Document and Entity Information - USD ($) $ in Billions	12 Months Ended
Document and Entity Information - USD ($) $ in Billions	Dec. 31, 2018	Feb. 06, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	TREX
Entity Registrant Name	TREX CO INC
Entity Central Index Key	0001069878
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		58,508,808
Entity Public Float			$ 3.6

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 684,250	$ 565,153	$ 479,616
Cost of sales	389,356	321,780	292,521
Gross profit	294,894	243,373	187,095
Selling, general and administrative expenses	118,225	100,993	83,140
Income from operations	176,669	142,380	103,955
Interest (income) expense, net	(192)	461	1,125
Income before income taxes	176,861	141,919	102,830
Provision for income taxes	42,289	46,791	34,983
Net income	$ 134,572	$ 95,128	$ 67,847
Basic earnings per common share	$ 2.29	$ 1.62	$ 1.16
Basic weighted average common shares outstanding	58,739,670	58,785,118	58,789,118
Diluted earnings per common share	$ 2.28	$ 1.61	$ 1.15
Diluted weighted average common shares outstanding	59,067,302	59,150,920	59,225,338
Comprehensive income	$ 134,572	$ 95,128	$ 67,847

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 105,699	$ 30,514
Accounts receivable, net	91,163	66,882
Inventories	57,801	34,524
Prepaid expenses and other assets	15,562	16,878
Total current assets	270,225	148,798
Property, plant and equipment, net	117,144	103,110
Goodwill and other intangibles	74,503	71,319
Other assets	3,250	3,000
Total Assets	465,122	326,227
Current Liabilities:
Accounts payable	31,084	9,953
Accrued expenses and other liabilities	56,291	46,266
Accrued warranty	5,400	6,290
Total current liabilities	92,775	62,509
Deferred income taxes	2,125	1,286
Non-current accrued warranty	25,354	28,709
Other long-term liabilities	1,905	2,473
Total Liabilities	122,159	94,977
Commitments and contingencies
Stockholders' Equity:
Preferred stock, $0.01 par value, 3,000,000 shares authorized; none issued and outstanding
Common stock, $0.01 par value, 120,000,000 shares authorized; 69,998,336 and 69,844,222 shares issued and 58,551,653 and 58,856,860 shares outstanding at December 31, 2018 and 2017, respectively	700	698
Additional paid-in capital	124,224	121,694
Retained earnings	416,942	282,370
Treasury stock, at cost, 11,446,683 and 10,987,362 shares at December 31, 2018 and 2017, respectively	(198,903)	(173,512)
Total Stockholders' Equity	342,963	231,250
Total Liabilities and Stockholders' Equity	$ 465,122	$ 326,227

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	3,000,000	3,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	69,998,336	69,844,222
Common stock, shares outstanding	58,551,653	58,856,860
Treasury stock, shares	11,446,683	10,987,362

Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings (Deficit) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2015	$ 116,462	$ 696	$ 116,598	$ 119,395	$ (120,227)
Beginning Balance, Shares at Dec. 31, 2015		61,809,060			7,829,458
Net income	67,847			67,847
Employee stock purchase and option plans	281	$ 2	279
Employee stock purchase and option plans, Shares		158,350
Shares withheld for taxes on share-based payment awards	(1,934)	$ (2)	(1,932)
Shares withheld for taxes on share-based payment awards, Shares		(26,386)
Stock-based compensation	4,790	$ 2	4,788
Stock-based compensation, Shares		17,984
Shares repurchased under our publicly announced share repurchase programs	(53,285)				$ (53,285)
Shares repurchased under our publicly announced share repurchase programs, Shares		(3,157,904)			3,157,904
Ending Balance at Dec. 31, 2016	134,161	$ 698	119,733	187,242	$ (173,512)
Ending Balance, Shares at Dec. 31, 2016		58,801,104			10,987,362
Net income	95,128			95,128
Employee stock purchase and option plans	393	$ 2	391
Employee stock purchase and option plans, Shares		33,228
Shares withheld for taxes on share-based payment awards	(3,619)	$ (2)	(3,617)
Shares withheld for taxes on share-based payment awards, Shares		(58,470)
Stock-based compensation	5,187		5,187
Stock-based compensation, Shares		80,998
Ending Balance at Dec. 31, 2017	231,250	$ 698	121,694	282,370	$ (173,512)
Ending Balance, Shares at Dec. 31, 2017		58,856,860			10,987,362
Net income	134,572			134,572
Employee stock purchase and option plans	882	$ 1	881
Employee stock purchase and option plans, Shares		63,448
Shares withheld for taxes on share-based payment awards	(4,695)		(4,695)
Shares withheld for taxes on share-based payment awards, Shares		(13,028)
Stock-based compensation	6,345	$ 1	6,344
Stock-based compensation, Shares		103,694
Shares repurchased under our publicly announced share repurchase programs	(25,391)				$ (25,391)
Shares repurchased under our publicly announced share repurchase programs, Shares		(459,321)			459,321
Ending Balance at Dec. 31, 2018	$ 342,963	$ 700	$ 124,224	$ 416,942	$ (198,903)
Ending Balance, Shares at Dec. 31, 2018		58,551,653			11,446,683

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities
Net income	$ 134,572	$ 95,128	$ 67,847
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	16,597	16,860	14,498
Deferred income taxes	1,037	194	5,433
Stock-based compensation	6,344	5,187	4,788
Loss (Gain) on disposal of property, plant and equipment	47	1,738	(185)
Other non-cash adjustments	(406)	(406)	(284)
Changes in operating assets and liabilities:
Accounts receivable	(24,281)	(10,486)	(653)
Inventories	(23,276)	(3,635)	(5,442)
Prepaid expenses and other assets	(613)	(2,194)	(4,256)
Accounts payable	21,131	(4,804)	(6,966)
Accrued expenses and other liabilities	5,040	2,488	9,403
Income taxes receivable/payable	1,929	1,795	1,110
Net cash provided by operating activities	138,121	101,865	85,293
Investing Activities
Expenditures for property, plant and equipment and intangibles	(33,816)	(15,040)	(14,551)
Proceeds from sales of property, plant and equipment	83	55	4,349
Acquisition of business, net of cash acquired		(71,804)
Net cash used in investing activities	(33,733)	(86,789)	(10,202)
Financing Activities
Financing costs			(485)
Borrowings under line of credit	172,250	201,000	242,700
Principal payments under line of credit	(172,250)	(201,000)	(249,700)
Repurchases of common stock	(30,085)	(3,617)	(55,216)
Proceeds from employee stock purchase and option plans	882	391	279
Net cash used in financing activities	(29,203)	(3,226)	(62,422)
Net increase in cash and cash equivalents	75,185	11,850	12,669
Cash and cash equivalents at beginning of year	30,514	18,664	5,995
Cash and cash equivalents at end of year	105,699	30,514	18,664
Supplemental disclosures of cash flow information:
Cash paid for interest	662	418	852
Cash paid for income taxes, net	$ 48,238	$ 44,802	$ 28,626

Business and Organization

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Business and Organization

1.	BUSINESS AND ORGANIZATION

Trex Company, Inc. (together with its subsidiaries, the Company), a Delaware corporation, was incorporated on September 4, 1998. The Company’s principal business based on net sales is the manufacture and distribution of wood/plastic composite products, as well as related accessories, primarily for residential and commercial decking and railing applications. A majority of its products are manufactured in a proprietary process that combines reclaimed wood fibers and scrap polyethylene. On July 31, 2017, through its newly-formed, wholly-owned subsidiary, Trex Commercial Products, Inc., the Company acquired certain assets and assumed certain liabilities of Staging Concepts Acquisition, LLC (SC Company) and thus expanded its markets to include the design, engineering and marketing of modular and architectural railing and staging systems for the commercial and multi-family market, including sports stadiums and performing arts venues. Additional information on the acquisition of SC Company is presented in Note 3. The principal executive offices are located at 160 Exeter Drive, Winchester, Virginia 22603, and the telephone number at that address is (540) 542-6300. Subsequent to the acquisition, the Company operates in two reportable segments, Trex Residential Products (Trex Residential) and Trex Commercial Products (Trex Commercial).

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Accounting

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States. The consolidated financial statements include the accounts of the Company, its wholly-owned subsidiary, Trex Wood-Polymer Espana, S.L. (TWPE) for all years presented, and its wholly-owned subsidiary, Trex Commercial Products, Inc. (Trex Commercial Products), from date of acquisition of July 31, 2017. Intercompany accounts and transactions have been eliminated in consolidation.

TWPE was formed to hold the Company’s 35% equity interest in Denplax, S.A. (Denplax), a venture with a Spanish company responsible for public environmental programs in southern Spain and with an Italian equipment manufacturer. The venture was formed to recycle polyethylene at a facility in El Ejido, Spain. The Company’s investment in Denplax is accounted for using the equity method. During 2010, the Company determined that its investment in Denplax and a related note receivable were no longer recoverable and recorded a $2.4 million charge to earnings to fully reserve the equity investment and note. Both the equity investment and note remain fully reserved as of December 31, 2018.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and the accompanying notes. Actual results could differ from those estimates.

Cash and Cash Equivalents

Cash equivalents consist of highly liquid investments purchased with original maturities of three months or less.

Concentrations and Credit Risk

The Company’s financial instruments that are exposed to concentrations of credit risk consist primarily of cash and cash equivalents and trade accounts receivable. The Company from time to time may have bank deposits in excess of insurance limits of the Federal Deposit Insurance Corporation. As of December 31, 2018, substantially all deposits are maintained in one financial institution. The Company has not experienced any losses in such accounts and believes it is not exposed to any significant credit risk related to its cash and cash equivalents.

The Company routinely assesses the financial strength of its customers and believes that its trade receivables credit risk exposure is limited. Trade receivables are recognized at the amount of revenue recognized on each shipment for Trex Residential products and for satisfied performance obligations for Trex Commercial products as the Company has an unconditional right to consideration from the customer and payment is due based solely on the passage of time. A valuation allowance is provided for known and anticipated credit losses and disputed amounts, as determined by management in the course of regularly evaluating individual customer receivables. This evaluation takes into consideration a customer’s financial condition and credit history, as well as current economic conditions. There was no material valuation allowance recorded as of December 31, 2018 and 2017.

In the years ended December 31, 2018, 2017 and 2016, sales to certain customers accounted for 10% or more of the Company’s total net sales. For the year ended December 31, 2018, two customers of the Company represented approximately 42% of the Company’s net sales. For the year ended December 31, 2017, two customers of the Company represented approximately 41% of the Company’s net sales. For the year ended December 31, 2016, two customers of the Company represented approximately 39% of the Company’s net sales. At December 31, 2018, four customers represented 31%, 19%, 13% and 12%, respectively, of the Company’s accounts receivable balance.

For each year ended December 31, 2018, 2017 and 2016, approximately 33% of the Company’s materials purchases were purchased from its four largest suppliers.

Inventories

Inventories for the Company’s wood-alternative decking and railing products are stated at the lower of cost (last-in, first-out, or LIFO, method) and market. The Company periodically reviews its inventory for slow moving or obsolete items and writes down the related products to estimated realizable value. The Company’s reserves for estimated slow moving products or obsolescence are not material. At December 31, 2018, the excess of the replacement cost of inventory over the LIFO value of inventory was approximately $18.4 million. Due to the nature of the LIFO valuation methodology, liquidations of inventories will result in a portion of the Company’s cost of sales being based on historical rather than current year costs.

A majority of the Company’s products are made in a proprietary process that combines reclaimed wood fibers and scrap polyethylene. The Company grinds up scrap materials generated from its manufacturing process and inventories deemed no longer salable and reintroduces the reclaimed material into the manufacturing process as a substitute for raw materials. The reclaimed material is valued at the costs of the raw material components of the material.

Inventories for the Company’s railing and staging products for the commercial and multi-family market are stated at the lower of cost (first-in, first-out or FIFO method), using actual cost, and net realizable value. Work-in process includes estimated production costs.

Property, Plant and Equipment

Property, plant and equipment are stated at historical cost. The costs of additions and improvements are capitalized, while maintenance and repairs are expensed as incurred. Depreciation is provided using the straight-line method over the following estimated useful lives:


Buildings		40 years
Machinery and equipment		3-11 years
Furniture and equipment		10 years
Forklifts and tractors		5 years
Computer equipment and software		5 years

Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset.

The Company reviews its long-lived assets, including property, plant and equipment, whenever events or changes in circumstances indicate that the carrying amount of the assets may not be fully recoverable. To determine the recoverability of its long-lived assets, the Company evaluates the probability that future estimated undiscounted net cash flows will be less than the carrying amount of the long-lived assets. If the estimated cash flows are less than the carrying amount of the long-lived assets, the assets are written down to their fair value. The Company’s estimates of anticipated cash flows and the remaining estimated useful lives of long-lived assets could be reduced in the future. As a result, the carrying amount of long-lived assets could be reduced in the future. Long-lived assets held for sale are stated at the lower of cost or fair value less cost to sell.

Fair Value Measurement

Assets and liabilities measured at fair value are measured at the amount that would be received for selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date and classified into one of the following fair value hierarchy:

•

Level 1 – Quoted prices for identical instruments in active markets.

•

Level 2 – Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model derived valuations in which all significant inputs and significant value drivers are observable in active markets.

•

Level 3 – Valuations derived from management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model.

Goodwill

Goodwill represents the excess of cost over net assets acquired resulting from the Company’s 1996 purchase of the Mobil Composite Products Division, the 2011 purchase of the assets of the Iron Deck Corporation, and the 2017 purchase of certain assets and the assumption of certain liabilities of SC Company. The Company evaluates the recoverability of goodwill in accordance with Accounting Standard Codification Topic 350, “Intangibles – Goodwill and Other,” annually or more frequently if an event occurs or circumstances change in the interim that would more likely than not reduce the fair value of the asset below its carrying amount. Goodwill is considered to be impaired when the net book value of the reporting unit exceeds its estimated fair value.

The Company first assesses qualitative factors to determine if it is more likely than not that the fair value of the reporting units is less than the carrying amount to determine if it should proceed with the evaluation of goodwill for impairment. The Company identified its reporting units based on the way it manages its operating segments. Each reporting unit constitutes a business with discrete financial information and operating segment management, at a level below the Company’s chief operating decision maker, regularly reviews the operating results of the reporting unit. The Company assigned goodwill to the reporting units based on the excess of the fair values acquired over the fair value of the sum of the individual assets acquired and liabilities assumed that were assigned to the reporting units. If the Company proceeds with the two-step impairment test, the Company first compares the fair value of the reporting unit to its carrying value. If the carrying value of a reporting unit exceeds its fair value, the goodwill of that reporting unit is potentially impaired and step two of the impairment analysis is performed. In step two of the analysis, an impairment loss is recorded equal to the excess of the carrying value of the reporting unit’s goodwill over its implied fair value should such a circumstance arise.

The Company measures fair value of the reporting units based on a present value of future discounted cash flows and a market valuation approach. The discounted cash flows model indicates the fair value of the reporting unit based on the present value of the cash flows that the reporting unit is expected to generate in the future. Significant estimates in the discounted cash flows model include: the weighted average cost of capital; long-term rate of growth and profitability of the business; and working capital effects. The market valuation approach indicates the fair value of the business based on a comparison of the Company against certain market information. Significant estimates in the market approach model include identifying appropriate market multiples and assessing earnings before interest, income taxes, depreciation and amortization (EBITDA) in estimating the fair value of the reporting unit.

For the years ended December 31, 2018, 2017 and 2016, the Company completed its annual impairment test of goodwill utilizing the qualitative assessment and concluded it was not more likely than not that the fair value of the reporting units are less than the carrying amounts. The Company performs the annual impairment testing of its goodwill as of October 31 of each year. However, actual results could differ from the Company’s estimates and projections, which would affect the assessment of impairment. As of December 31, 2018, the Company had goodwill of $68.5 million that is reviewed annually for impairment.

Product Warranty

The Company warrants that its Trex Residential decking products will be free from material defects in workmanship and materials. This warranty generally extends for a period of 25 years for residential use and 10 years for commercial use. With respect to Trex Signature^® Railing, the warranty period is 25 years for both residential and commercial use. With respect to the Company’s Transcend^®, Enhance^®, Select^® and Universal Fascia product, the Company further warrants that the product will not fade in color more than a certain amount and will be resistant to permanent staining from food substances or mold, provided the stain is cleaned within seven days of appearance. This warranty extends for a period of 25 years for residential use and 10 years for commercial use. If there is a breach of such warranties, the Company has an obligation either to replace the defective product or refund the purchase price. The Company also warrants its Trex Commercial products for one to three years. The Company establishes warranty reserves to provide for estimated future expenses as a result of product defects that result in claims. Reserve estimates are based on management’s judgment, considering such factors as cost per claim, historical experience, anticipated rates of claims, and other available information. Management reviews and adjusts these estimates, if necessary, based on the differences between actual experience and historical estimates.

Treasury Stock

The Company records the repurchase of shares of its common stock at cost. These shares are considered treasury stock, which is a reduction to stockholders’ equity. Treasury stock is included in authorized and issued shares but excluded from outstanding shares.

Revenue Recognition

Effective January 1, 2018, the Company retrospectively adopted the requirements of Financial Accounting Standards Board Accounting Standards Update 2014-09, “Revenue from Contracts with Customers” (Topic 606). The Company determined the appropriate revenue recognition for its contracts with customers by analyzing the type, terms and conditions of the contracts with customers. Topic 606 provides a single, comprehensive model for revenue recognition arising from contracts with customers. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in Topic 606. A contract’s transaction price is allocated to each distinct performance obligation and revenue is recognized when or as the Company satisfies the performance obligation. Revenue is recognized at an amount that reflects the consideration to which the entity expects to be entitled in exchange for transferring control of the goods or services to a customer. Adoption of Topic 606 did not have an impact on the Company’s financial condition or results of operations. The following provides additional information about the Company’s contracts with customers.

Trex Residential Products

Trex Residential principally generates revenue from the manufacture and sale of its high performance, low maintenance composite decking and railing products and accessories. Substantially all of its revenues are from contracts with customers, which are individual customer purchase orders of short-term duration of less than one year. Trex Residential satisfies its performance obligations at a point in time. The shipment of each product is a separate performance obligation as the customer is able to derive benefit from each product shipped and no performance obligation remains after shipment. Upon shipment of the product, the customer obtains control over the distinct product and Trex Residential satisfies its performance obligation. Any performance obligation that remains unsatisfied at the end of a reporting period is part of a contract that has an original expected duration of one year or less. Any variable consideration related to the unsatisfied performance obligation is allocated wholly to the unsatisfied performance obligation and recognized when the product ships and the performance obligation is satisfied.

Trex Commercial Products

Trex Commercial generates revenue from the manufacture and sale of its modular and architectural railing and staging systems. All of its revenues are from fixed-price contracts with customers. Trex Commercial contracts have a single performance obligation as the promise to transfer the individual goods or services is not separately identifiable from other promises in the contract and is, therefore, not distinct.

Trex Commercial satisfies its performance obligation over time as work progresses because control is transferred continuously to its customers. Revenue and estimated profit is recognized over time based on the proportion of actual costs incurred to date relative to total estimated costs at completion to measure progress toward satisfying the performance obligation. Incurred costs represent work performed, which corresponds with, and thereby best depicts, the transfer of control to the customer. Incurred costs include all direct material, labor, subcontract and certain indirect costs. The Company reviews and updates its estimates regularly and recognizes adjustments in estimated profit on contracts under the cumulative catch-up method. Under this method, the impact of the adjustment on revenue and estimated profit to date on a contract is recognized in the period the adjustment is identified. Revenues and profits in future periods are recognized using the adjusted estimate. If at any time the estimate of contract profitability indicates an anticipated loss on the contract, the Company recognizes the total loss in the period it is identified. During the year ended December 31, 2018, no adjustment to any one contract was material to the Company’s Consolidated Financial Statements and no material impairment loss on any contract was recorded.

Stock-Based Compensation

The Company measures stock-based compensation at the grant date of the award based on the fair value. For stock options, stock appreciation rights and time-based restricted stock and time-based restricted stock units, stock-based compensation is recognized on a straight line basis over the vesting periods of the award. The Company recognizes forfeitures as they occur. For performance-based restricted stock and performance-based restricted stock units, expense is recognized ratably over the performance and vesting period of each tranche based on management’s judgment of the ultimate award that is probable to be paid out based on the achievement of predetermined performance measures. Stock-based compensation expense is included in “Selling, general and administrative expenses” in the accompanying Consolidated Statements of Comprehensive Income.

Income Taxes

The Company recognizes deferred tax assets and liabilities based on the difference between the financial statement basis and tax basis of assets and liabilities using enacted rates expected to be in effect during the year in which the differences reverse. The Company assesses the likelihood that its deferred tax assets will be realized. Deferred tax assets are reduced by a valuation allowance when, after considering all available positive and negative evidence, it is determined that it is more likely than not that some portion, or all, of the deferred tax asset will not be realized. The tax legislation H.R.1, “An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018,” known as the Tax Cuts and Jobs Act (Act), was enacted on December 22, 2017. Accordingly, the Company recognized the tax effects of the Act in its financial statements and related notes. As of December 31, 2018, the Company has a valuation allowance of $3.0 million against these deferred tax assets. The Company analyzes its position in subsequent reporting periods, considering all available positive and negative evidence, in determining the expected realization of its deferred tax assets.

Research and Development Costs

Research and development costs are expensed as incurred. For the years ended December 31, 2018, 2017 and 2016, research and development costs were $4.2 million, $3.8 million, and $3.7 million, respectively, and have been included in “Selling, general and administrative expenses” in the accompanying Consolidated Statements of Comprehensive Income.

Advertising Costs

The Company expenses its branding and advertising communication costs as incurred. Significant production costs are deferred and recognized as expense in the period that the related advertisement is first used. At December 31, 2017 and 2016, $3.8 million, and $2.4 million, respectively, were included in prepaid expenses for production costs. At December 31, 2018 there were no production costs included in prepaid expenses.

For the years ended December 31, 2018, 2017 and 2016, branding expenses, including advertising expenses as described above, were $35.0 million, $31.0 million, and $24.8 million, respectively.

Fair Value of Financial Instruments

The Company considers the recorded value of its financial assets and liabilities, consisting primarily of cash and cash equivalents, accounts receivable, accounts payable, accrued expenses and other current liabilities to approximate the fair value of the respective assets and liabilities on the Consolidated Balance Sheets at December 31, 2018 and 2017.

Recently Adopted Accounting Standards

In May 2017, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2017-09, “Compensation—Stock Compensation (Topic 718), Scope Modification Accounting.” The guidance clarified when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value (or calculated intrinsic value, if those amounts are being used to measure the award under ASC 718), the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The guidance was effective prospectively for annual periods beginning on or after December 15, 2017. Adoption of the new standard did not have a material impact on the Company’s financial condition or results of operations.

In January 2017, the FASB issued ASU No. 2017-01, “Business Combinations (Topic 805), Clarifying the Definition of a Business.” The guidance requires an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets: if so, the set of transferred assets and activities is not a business. The guidance was effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Adoption of the new standard did not have a material impact on the Company’s financial condition or results of operations.

In August 2016, the FASB issued ASU No. 2016-15, “Statement of Cash flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments.” The guidance is intended to reduce diversity in practice across all industries in how certain transactions are classified in the statement of cash flows. The guidance was effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Adoption of the new standard did not have a material impact on the Company’s consolidated financial statements.

In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” and issued subsequent amendments to the initial guidance in August 2015 within ASU No. 2015-14, in March 2016 within ASU No. 2016-08, in April 2016 within ASU No. 2016-10, in May 2016 within ASU No. 2016-12, and in December 2016 within ASU No. 2016-20 (collectively, Topic 606). The Company adopted Topic 606 on January 1, 2018 and applied Topic 606 under the full retrospective method. The Company determined the appropriate revenue recognition for its contracts with customers by analyzing the type, terms and conditions of its contracts with its customers. The Company has consistently applied the accounting policies to all periods presented in these Consolidated Financial Statements. Adoption of Topic 606 did not have an impact on the Company’s financial condition or results of operations other than increased disclosures. Refer to Note 12, “Revenue from Contracts with Customers,” for a discussion of the Company’s accounting policy related to revenue from contracts with customers

New Accounting Standards Not Yet Adopted

In June 2018, the FASB issued ASU No. 2018-07, “Compensation – Stock Compensation (Topic 718).” The ASU expands the scope of Topic 718, which currently only includes share-based payments issued to employees, to also include share-based payments issued to nonemployees for goods or services. The ASU supersedes Subtopic 505-50, “Equity—Equity-Based Payment to Non-Employees.” Consequently, the accounting for share-based payments to nonemployees and employees will be substantially aligned. The ASU is effective for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. Early adoption is permitted. The Company intends to adopt the guidance on January 1, 2019 and does not believe adoption will have a material impact on its financial condition or results of operations.

In January 2017, the FASB issued ASU No. 2017-04, “Intangibles—Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment.” The guidance removes Step 2 of the goodwill impairment test and eliminates the need to determine the fair value of individual assets and liabilities to measure goodwill impairment. A goodwill impairment will now be the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. Entities will continue to have the option to perform a qualitative assessment to determine if a quantitative impairment test is necessary. The guidance will be applied prospectively, and is effective for annual and interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for any impairment tests performed on testing dates after January 1, 2017. The Company intends to adopt the guidance on January 1, 2020 and does not believe adoption will have a material impact on its financial condition or results of operations.

In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842),” and issued subsequent amendments to the initial guidance in January 2018 within ASU No. 2018-01 and in July 2018 within ASU Nos. 2018-10 and 2018-11. The standard requires lessees to recognize leases on the balance sheet as a right-of-use asset and a lease liability, other than leases that meet the definition of a short-term lease. The liability will be equal to the present value of the lease payments. The asset will be based on the liability, subject to adjustment. Currently, under existing U.S. generally accepted accounting principles, the Company does not recognize on the balance sheet a right-of-use asset or lease liability related to its operating leases. For income statement purposes, the leases will continue to be classified as either operating or finance. Operating leases will result in straight-line expense (similar to current operating leases) and finance leases will result in a front-loaded expense pattern (similar to current capital leases). The standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted. The standard allows an entity to elect to have a date of initial application as of the beginning of the period of adoption. The standard provides for the option to elect a package of practical expedients upon adoption. The Company intends to adopt the standard on January 1, 2019 and is currently planning on electing the package of practical expedients to not reassess prior conclusions related to contracts containing leases, lease classification and initial direct costs and is evaluating the other practical expedients available under the guidance. The Company expects expanded financial statement note disclosure in addition to recognizing a right-of-use asset and lease liability for its operating leases on the balance sheet. Based on leases outstanding at December 31, 2018, the Company estimates the operating lease right of use asset and lease liability would have been in the range of $45 million to $50 million The Company continues to evaluate the impacts of the pending adoption. As such, the Company’s preliminary assessments are subject to change.

Acquisition

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Acquisition

3.	ACQUISITION

On July 31, 2017, through its newly-formed, wholly-owned subsidiary, Trex Commercial Products, Inc., the Company acquired certain assets and assumed certain liabilities of SC Company for $71.8 million in cash. The Company used cash on hand and $30.0 million of funding from its existing revolving credit facility, which was fully paid on August 17, 2017, to acquire the assets. The acquired business designs, engineers and markets modular architectural railing and staging systems for the commercial and multi- family market, including sports stadiums and performing arts venues. As a result of the purchase, the Company gained access to growing commercial markets, expanded its custom design and engineering capabilities, and added the contract architect and specifier communities as new channels for its products.

The acquisition was accounted for using the acquisition method of accounting under U.S. Generally Accepted Accounting Principles, which requires, among other things, that the assets acquired and liabilities assumed be recognized at their fair values as of the acquisition date. The fair values of consideration transferred and net assets acquired were determined using a combination of Level 2 and Level 3 inputs as specified in the fair value hierarchy in ASC 820, “Fair Value Measurements and Disclosures.” The Company believes that the fair values assigned to the assets acquired and liabilities assumed are based on reasonable assumptions. The Company’s consolidated results of operations include the operating results of the acquired business from the date of acquisition. The Company’s consolidated balance sheets at December 31, 2018 and December 31, 2017 includes the acquired assets and any liabilities assumed.

Based on the Company’s valuation, total consideration of $71.8 million was allocated to the assets acquired and liabilities assumed, as follows (in thousands):


Accounts receivable, net	$	8,357
Contract retainage		1,948
Inventories, net		2,344
Prepaid expenses and other assets		1,223
Revenues in excess of billings		3,463
Fixed assets, net		1,264
Intangible assets		4,900
Goodwill		57,938
Accounts payable		(3,990	)
Accrued liabilities and other expenses		(2,329	)
Billings in excess of revenues		(1,752	)
Customer deposits		(1,562	)

Total consideration	$	71,804

Goodwill of $57.9 million is primarily attributable to the potential opportunity for the Company to offer full service railing systems in the growing commercial and multi-family markets, access to a complementary product category with a track record of substantial revenue growth, the ability to achieve economies of scale around raw material procurement, an increase in the range of products the Company may offer its core customers, and intangible assets that do not qualify for separable or legal criterion, such as an assembled workforce. The amount of goodwill that was amortized and deductible for tax purposes in 2018 and 2017 was $3.9 million and $1.6 million, respectively. Primarily all of the goodwill was recorded to Trex Commercial. The fair value attributed to intangible assets, which consists of production backlog and trade names and trademarks, is being amortized straight line over 12 months and is based on the estimated economics of the assets. The fair value attributed to the intangible assets acquired and goodwill was based on assumptions and other information compiled by management, including independent valuations that utilized established valuation techniques.

During the year ended December 31, 2018, Trex Commercial generated $71.0 million of net sales and $2.7 million of net income, which included amortization expense of $2.9 million. From July 31, 2017, through December 31, 2017, Trex Commercial generated $21.8 million in net sales and incurred a net loss of $2.3 million, and which included $0.5 million of acquisition-related expenses and $2.0 million of amortization expense during the year ended December 31, 2017, which are included in selling, general and administrative expense.

Inventories

12 Months Ended

Dec. 31, 2018

Inventory Disclosure [Abstract]

Inventories

4.	INVENTORIES

Inventories (at LIFO value) consist of the following as of December 31 (in thousands):


	2018			2017
Finished goods	$	46,638		$	32,986
Raw materials		27,321			19,432

Total FIFO (first-in, first out) inventories		73,959			52,418
Reserve to adjust inventories to LIFO value		(18,442	)		(20,070	)

Total LIFO inventories	$	55,517		$	32,348

Inventory related to the Company’s wood-alternative decking and railing products is stated at the lower of LIFO cost or market. The Company periodically reviews its inventory for slow moving or obsolete items and writes down the related products to estimated market.

Under the LIFO method, reductions in inventory cause a portion of the Company’s cost of sales to be based on historical costs rather than current year costs. There was no inventory reduction during 2018 and 2017.

Inventories valued at lower of cost (FIFO method) and net realizable value as of December 31, 2018 and December 31, 2017, consist of $2.3 million and $2.2 million, respectively, of raw materials. The Company utilizes the FIFO method of accounting related to its commercial products.

Goodwill and Other Intangible Assets

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Other Intangible Assets

6.	GOODWILL AND OTHER INTANGIBLE ASSETS

The carrying amount of goodwill by reportable segment at December 31, 2018 and 2017 was $14.2 million for Trex Residential and $54.3 million for Trex Commercial.

Intangible assets consist of the following (in thousands):


	December 31, 2018			December 31, 2017
Intangible assets:
Customer backlog	$	4,000		$	4,000
Trade names and trademarks		900			900
Domain names		6,327			—

Total intangible assets		11,227			4,900

Accumulated amortization:
Customer backlog		(4,000	)		(1,666	)
Trade name and trademarks		(900	)		(376	)
Domain names		(285	)		—

Total accumulated amortization		(5,185	)		(2,042	)

Intantible assets, net	$	6,042		$	2,858

Intangible asset amounts were determined based on the estimated economics of the asset and are amortized over the estimated useful lives on a straight-line basis over 12 months for customer backlog and trade names and trademarks and 15 years for domain names, which approximates the pattern in which the economic benefits are expected to be received. In May 2018, the Company purchased certain domain names for $6.3 million. We evaluate the recoverability of intangible assets periodically and consider events or circumstances that may warrant revised estimates of useful lives or that may indicate an impairment. Intangible asset amortization expense for the years ended December 31, 2018 and December 31, 2017, was $3.1 million and $2.0 million, respectively.

Property, Plant and Equipment

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

7.	PROPERTY, PLANT AND EQUIPMENT

Property, plant and equipment consist of the following as of December 31 (in thousands):


	2018			2017
Building and improvements	$	50,240		$	49,403
Machinery and equipment		233,464			228,107
Furniture and fixtures		1,625			1,620
Forklifts and tractors		10,872			9,799
Computer equipment		10,142			9,680
Construction in process		16,392			5,954
Land		11,417			11,417

Total property, plant and equipment		334,152			315,980
Accumulated depreciation		(217,008	)		(212,870	)

Total property, plant and equipment, net	$	117,144		$	103,110

The Company had construction in process as of December 31, 2018 of approximately $16.4 million. The Company expects that the construction in process will be completed and put into service in the year ending December 31, 2019.

Depreciation expense for the years ended December 31, 2018, 2017, and 2016 totaled $13.4 million, $14.7 million, and $14.2 million, respectively.

Accrued Expenses and Other Liabilities

12 Months Ended

Dec. 31, 2018

Payables and Accruals [Abstract]

Accrued Expenses and Other Liabilities

8.	ACCRUED EXPENSES AND OTHER LIABILITIES

Accrued expenses and other liabilities consist of the following as of December 31 (in thousands):


	2018		2017
Sales and marketing costs	$	25,379	$	21,964
Compensation and benefits		19,124		14,818
Manufacturing costs		3,744		1,979
Customer deposits		2,058		1,230
Rent obligations		663		779
Billings in excess of revenues		512		1,842
Other		4,811		3,654

Total accrued expenses	$	56,291	$	46,266

Debt

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Debt

DEBT

The Company’s debt consists of a revolving credit facility. At December 31, 2018 and 2017, the Company had no outstanding indebtedness. Available borrowing capacity at December 31, 2018, was $200 million.

Revolving Credit Facility

On January 12, 2016, the Company entered into a Third Amended and Restated Credit Agreement and also the First Amendment to the Third Amended and Restated Credit Agreement (together, the Third Amended Credit Agreement) with Bank of America, N.A. (BOA) as Lender, Administrative Agent, Swing Line Lender and Letter of Credit Issuer; and certain other lenders including Citibank, N.A., Capital One, N.A., and SunTrust Bank (collectively, Lenders) arranged by Bank of America Merrill Lynch as Sole Lead Arranger and Sole Bookrunner. The Third Amended Credit Agreement amended and restated the Second Amended Credit Agreement.

Under the Third Amended Credit Agreement, the Lenders agree to provide the Company with one or more revolving loans in a collective maximum principal amount of $250 million from January 1 through June 30 of each year and a maximum principal amount of $200 million from July 1 through December 31 of each year throughout the term, which ends January 12, 2021. Included within the revolving loan limit are sublimits for a letter of credit facility in an amount not to exceed $15 million and swing line loans in an aggregate principal amount at any time outstanding not to exceed $5 million. The revolving loans, the letter of credit facility and the swing line loans are for the purpose of funding working capital needs and supporting general business operations. Additionally, within the Revolving Loan Limit, the Company could borrow, repay, and reborrow, at any time or from time to time while the Third Amended Credit Agreement is in effect.

The Company has the option to select interest rates for each loan request at the Base Rate or Eurodollar Rate. Base rate loans under the revolving loans and the swing line loans accrue interest at the Base Rate plus the Applicable Rate. Eurodollar Rate Loans for the revolving loans and swing line loans accrue interest at the Adjusted London InterBank Offered Rate plus the Applicable Rate. The Base Rate for any day is a fluctuating rate per annum equal to the highest of (a) the Federal Funds Rate plus 0.50%, (b) the rate of interest in effect for such day as publicly announced from time to time by BOA as its prime rate, and (c) the Eurodollar Rate plus 1.0%. Repayment of all then outstanding principal, interest, fees and costs is due on January 12, 2021.

The Company shall reimburse BOA for all amounts payable, including interest, under a letter of credit at the earlier of (i) the date set forth in the application, or (ii) one business day after the payment under such letter of credit by BOA.

The Third Amended Credit Agreement is secured by property with respect to which liens in favor of the Administrative Agent, for the benefit of itself and the other holders of the obligations, are purported to be granted pursuant to and in accordance with the terms of the collateral documents as referenced in the Third Amended Credit Agreement.

Compliance with Debt Covenants and Restrictions

The Company’s ability to make scheduled principal and interest payments, borrow and repay amounts under any outstanding revolving credit facility and continue to comply with any loan covenants depends primarily on its ability to generate sufficient cash flows from operations. To remain in compliance with financial covenants, the Company is required to maintain specified financial ratios based on levels of debt, fixed charges, and earnings (excluding extraordinary gains and extraordinary non-cash losses) before interest, taxes, depreciation and amortization, all of which are subject to the risks of the business, some of which are discussed in this report under “Risk Factors.” The material financial covenants and restrictions do not permit the Company’s fixed charge coverage ratio to be less than 1.5 to 1.0 and do not permit the Company’s consolidated debt to consolidated EBITDA ratio to exceed 3.0 to 1.0, measured as of the end of each fiscal quarter (and in the case of Consolidated EBITDA, for the four-quarter period ending on such date). The Company was in compliance with all covenants contained in the Third Amended Credit Agreement at December 31, 2018. Failure to comply with the financial covenants could be considered a default of repayment obligations and, among other remedies, could accelerate payment of any amounts outstanding.

Stockholders' Equity

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Stockholders' Equity

11.

STOCKHOLDERS’ EQUITY

Amendment of Restated Certificate of Incorporation

The Company’s Board of Directors unanimously approved an amendment to the Company’s Restated Certificate of Incorporation (Amendment) on February 14, 2018, subject to stockholder approval. At the annual meeting of stockholders of the Company held on May 2, 2018, the Company’s stockholders approved the Amendment, effective as of May 2, 2018. The Amendment increased the number of shares of common stock, par value $.01 per share, that the Company is authorized to issue from 80,000,000 shares to 120,000,000 shares. The Amendment was filed with the Delaware Secretary of State on May 2, 2018.

Stock Split

On May 2, 2018, the Board of Directors of the Company approved a two-for-one stock split of the Company’s common stock, par value $0.01. The stock split was in the form of a stock dividend distributed on June 18, 2018, to stockholders of record at the close of business on May 23, 2018. The stock split entitled each stockholder to receive one additional share of common stock, par value $0.01, for each share they held as of the record date. All common stock share and per share data for all periods presented in the accompanying consolidated financial statements and notes thereto have been retroactively adjusted to reflect the stock split.

Earnings Per Share

The following table sets forth the computation of basic and diluted earnings per share (in thousands, except share and per share data):


	Year Ended December 31,
	2018		2017		2016
Numerator:
Net income	$	134,572	$	95,128	$	67,847

Denominator:
Basic weighted average shares outstanding		58,739,670		58,785,118		58,789,118
Effect of dilutive securities:
Stock appreciation rights		176,700		198,642		250,238
Restricted stock		150,932		167,160		185,982

Diluted weighted average shares outstanding		59,067,302		59,150,920		59,225,338

Basic earnings per share	$	2.29	$	1.62	$	1.16

Diluted earnings per share	$	2.28	$	1.61	$	1.15

Diluted earnings per share is computed using the weighted average number of shares determined for the basic earnings per share computation plus the dilutive effect of common stock equivalents using the treasury stock method. The computation of diluted earnings per share excludes the following potentially dilutive securities because the effect would be anti-dilutive:


	Year Ended December 31,
	2018		2017		2016
Restricted stock		214		166		24
Stock appreciation rights		13,347		21,234		9,262

Stock Repurchase Programs

On October 22, 2015, the Board of Directors adopted a stock repurchase program of up to 3.15 million shares of the Company’s outstanding common stock (October 2015 Stock Repurchase Program). This authorization terminated on December 31, 2016. During 2016, the Company repurchased 1,578,952 shares for $53.3 million under the October 2015 Stock Repurchase Program.

On February 16, 2017, the Board of Directors authorized a common stock repurchase program of up to 2.961 million shares of the Company’s outstanding common stock (February 2017 Stock Repurchase Program). The Company made no repurchases under the February 2017 Stock Repurchase Program.

On February 16, 2018, the Board of Directors terminated the February 2017 Stock Repurchase Program and adopted a new stock repurchase program of up to 5.8 million shares of the Company’s outstanding common stock (February 2018 Stock Repurchase Program). As of the date of this report, the Company has repurchased 459,321 shares under the February 2018 Stock Repurchase Program.

Revenue From Contract With Customer

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Revenue From Contract With Customer

12.

REVENUE FROM CONTRACTS WITH CUSTOMERS

Topic 606 provides a single, comprehensive model for revenue recognition arising from contracts with customers. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in Topic 606. A contract’s transaction price is allocated to each distinct performance obligation and revenue is recognized when or as the Company satisfies the performance obligation. Revenue is recognized at an amount that reflects the consideration to which the entity expects to be entitled in exchange for transferring control of the goods or services to a customer.

Trex Residential Products

Trex Residential principally generates revenue from the manufacture and sale of its high performance, low maintenance composite decking and residential railing products and accessories. Substantially all of its revenues are from contracts with customers, which are purchase orders of short-term duration of less than one year. Its customers, in turn, sell primarily to the residential market, which includes replacement, remodeling and new construction related to outdoor living products. Trex Residential satisfies its performance obligations at a point in time. The shipment of each product is a separate performance obligation as the customer is able to derive benefit from each product shipped and no performance obligation remains after shipment. Upon shipment of the product, the customer obtains control over the distinct product and Trex Residential satisfies its performance obligation. Any performance obligation that remains unsatisfied at the end of a reporting period is part of a contract that has an original expected duration of one year or less. Any variable consideration related to the unsatisfied performance obligation is allocated wholly to the unsatisfied performance obligation and recognized when the product ships and the performance obligation is satisfied.

For each product shipped, the transaction price by product is specified in the purchase order. The Company recognizes revenue on the transaction price less any amount offered under a sales incentive program. The Company recognizes an account receivable (contract asset) for the amount of revenue recognized as it has an unconditional right to consideration at the time of shipment and payment from the customer is due based solely on the passage of time. The Company receives payments from its customers based on the payment terms applicable to each individual contract and the customer pays in accordance with the billing terms specified in the purchase order, which is less than one year. The related accounts receivables are included in “Accounts receivable, net” in the Consolidated Balance Sheets.

Trex Residential may offer various sales incentive programs throughout the year. It estimates the amount of sales incentive to allocate to each performance obligation, or product shipped, based on direct sales to the customer. The estimate is updated each reporting period and any changes are allocated to the performance obligations on the same basis as at inception. Changes in estimate allocated to a previously satisfied performance obligation are recognized as a reduction of revenue in the period in which the change occurs under the cumulative catch-up method. In addition to sales incentive programs, Trex Residential may offer a payment discount. It estimates the payment discount that it believes will be taken by the customer based on prior history.

Trex Residential pays commissions to certain employees. However, the sales commissions are not directly attributable to identifiable contracts, are discretionary in nature and are based on other factors not related to obtaining a contract, such as individual performance, profitability of the entity, annual sales targets, etc. These costs are included in selling, general and administrative expenses as incurred. Trex Residential does not grant contractual product return rights to customers other than pursuant to its assurance product warranty (see related disclosure on product warranties in Note 19, “Commitments and Contingencies”). Trex Residential accounts for all shipping and handling fees invoiced to the customer in net sales and the related costs in cost of sales.

Trex Commercial Products

Trex Commercial satisfies its performance obligation over time as work progresses because control is transferred continuously to its customers. Revenue and estimated profit is recognized over time based on the proportion of actual costs incurred to date relative to total estimated costs at completion to measure progress toward satisfying the performance obligation. Incurred costs represent work performed, which corresponds with, and thereby best depicts, the transfer of control to the customer. Incurred costs include all direct material, labor, subcontract and certain indirect costs. The Company reviews and updates its estimates regularly and recognizes adjustments in estimated profit on contracts under the cumulative catch-up method. Under this method, the impact of the adjustment on revenue and estimated profit to date on a contract is recognized in the period the adjustment is identified. Revenues and profits in future periods are recognized using the adjusted estimate. If at any time the estimate of contract profitability indicates an anticipated loss on the contract, the Company recognizes the total loss in the period it is identified. During the year ended December 31, 2018, no adjustment to any one contract was material to the Company’s Consolidated Financial Statements. In accordance with ASC 606-10-50-15, the Company discloses only the transaction price allocated to its remaining performance obligations on contracts with an original duration greater than one year, which was $49.1 million as of December 31, 2018. The Company will recognize this revenue as performance obligations are satisfied, which is expected to occur within the next 18 months.

The Company recognizes an account receivable (contract asset) for satisfied performance obligations as it has an unconditional right to consideration and payment from the customer is due based solely on the passage of time. The Company receives payments from its customers on the accounts receivable based on the payment terms applicable to each individual contract and the customer pays in less than one year. Accounts receivables are included in “Accounts receivable, net” in the Consolidated Balance Sheets.

In addition, the timing of revenue recognition, billings and cash collections may result in revenues in excess of billings and contract retainage (contract assets), and billings in excess of revenues and customer deposits (contract liabilities). These assets and liabilities are reported on a contract-by-contract basis at the end of each reporting period in prepaid expenses and other assets (contract assets), and accrued expenses and other liabilities (contract liabilities). These assets and liabilities and changes in these assets and liabilities, respectively, were not material as of and for the year ended December 31, 2018.

Trex Commercial pays sales commissions that are directly attributable to identifiable contracts to certain of its employees. If the amortization period of the commission is one year or less then the Company recognizes the commission expense as incurred. Otherwise, the Company capitalizes the commission and amortizes it on a straight-line basis over the life of the contract. Trex Commercial does not grant contractual product return rights to customers other than pursuant to its assurance product warranty. All shipping and handling fees invoiced to the customer are included in net sales and the related costs are included in cost of sales.

For the years ended December 31, 2018 and December 31, 2017, net sales were disaggregated in the following tables by (1) market (2) timing of revenue recognition, and (3) type of contract. The tables also include a reconciliation of the respective disaggregated net sales with the Company’s reportable segments (in thousands).


Year Ended December 31, 2018	Reportable Segment
	Trex Residential		Trex Commercial		*Total*
Timing of Revenue Recognition and Type of Contract
Products transferred at a point in time and variable consideration contracts	$	613.229	$	—	$	613,229
Products transferred over time and fixed price contracts		—		71,021		71,021

	$	613,229	$	71,021	$	684,250


Year Ended December 31, 2017	Reportable Segment
	Trex Residential		Trex Commercial		*Total*
Timing of Revenue Recognition and Type of Contract
Products transferred at a point in time and variable consideration contracts	$	543,346	$	—	$	543,346
Products transferred over time and fixed price contracts		—		21,807		21,807

	$	543,346	$	21,807	$	565,153

Stock-Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

13.

STOCK-BASED COMPENSATION

On April 30, 2014, the Company’s stockholders approved the Trex Company, Inc. 2014 Stock Incentive Plan (Plan), which was previously approved by the Board of Directors on February 19, 2014. The Plan amended and restated in its entirety the Trex Company, Inc. 2005 Stock Incentive Plan, as previously disclosed. The Plan is administered by the Compensation Committee of the Company’s Board of Directors. Stock-based compensation is granted to officers, directors and certain key employees in accordance with the provisions of the Plan. The Plan provides for grants of stock options, restricted stock, restricted stock units, stock appreciation rights (SARs), and unrestricted stock. The total aggregate number of shares of the Company’s common stock that may be issued under the Plan is 12,840,000.

The Company recognizes stock-based compensation expense ratably over the period from grant date to the earlier of (1) the vesting date of the award, or (2) the date the grantee is eligible to retire without forfeiting the award. For performance-based restricted stock and performance-based restricted stock units, expense is recognized ratably over the performance and vesting period of each tranche based on management’s judgment of the ultimate award that is probable to be paid out based on the achievement of the predetermined performance measures. For the employee stock purchase plan, compensation expense is recognized related to the discount on purchases. The following table summarizes the Company’s stock-based compensation expense (in thousands):


	Year Ended December 31,
	2018		2017		2016
Time-based restricted stock and time-based restricted stock units	$	2,687	$	1,992	$	2,281
Performance-based restricted stock and performance-based restricted stock units		3,144		2,805		2,210
Stock appreciation rights		370		251		184
Employee stock purchase plan		143		139		113

Total stock-based compensation	$	6,344	$	5,187	$	4,788

Stock-based compensation expense is included in “Selling, general and administrative expenses” in the accompanying Consolidated Statements of Comprehensive Income.

Time-Based Restricted Stock and Time-Based Restricted Stock Units

The fair value of time-based restricted stock and time-based restricted stock units is determined based on the closing price of the Company’s shares on the grant date. Time-based restricted stock and time-based restricted stock units vest based on the terms of the awards. Unvested time-based restricted stock and unvested time-based restricted stock units are generally forfeitable upon the resignation of employment or termination of employment with cause. The total fair value of vested time-based restricted shares and vested time-based restricted stock units for the years ended December 31, 2018, 2017 and 2016 was $5.1 million, $5.5 million, and $1.7 million, respectively. At December 31, 2018, there was $4.2 million of total compensation expense related to unvested time-based restricted stock and unvested time-based restricted stock units remaining to be recognized over a weighted-average period of approximately 2.7 years.

Time-based restricted stock and restricted stock unit activity under the Plan and all predecessor stock incentive plans is as follows:


	Time-based Restricted Stock and Restricted Stock Unit			Weighted-Average Grant Price Per Share
Nonvested at December 31, 2015		215,814		$	14.72
Granted		115,748		$	18.82
Vested		(87,696	)	$	21.17
Forfeited		(266	)	$	21.95

Nonvested at December 31, 2016		243,600		$	15.80
Granted		72,402		$	36.27
Vested		(162,372	)	$	14.45
Forfeited		(512	)	$	18.68

Nonvested at December 31, 2017		153,118		$	26.90
Granted		87,264		$	54.72
Vested		(84,550	)	$	26.65
Forfeited		(284	)	$	35.05

Nonvested at December 31, 2018		155,548		$	42.68

Performance-based Restricted Stock and Performance-Based Restricted Stock Units

The fair value of performance-based restricted stock and performance-based restricted stock units is determined based on the closing price of the Company’s shares on the grant date. Unvested performance-based restricted stock and unvested performance-based restricted stock units are generally forfeitable upon the resignation of employment or termination of employment with cause. The performance-based restricted shares and performance-based restricted stock units have a three-year vesting period, vesting one-third each year based on target earnings before interest, taxes, depreciation and amortization (EBITDA) for 1 year, cumulative 2 years and cumulative 3 years, respectively. The number of shares that will vest, with respect to each vesting, will be between 0% and 200% of the target number of shares. At December 31, 2018, 2017, and 2016 there was $1.6 million, $1.8 million, and $1.2 million, respectively, of total compensation expense related to unvested performance-based restricted stock and unvested performance-based restricted stock units remaining to be recognized over a weighted-average period of approximately 1.5 years.

Performance-based restricted stock activity under the Plan is as follows:


	Performance-based Restricted Stock and Performance-based Restricted Stock Units			Weighted-Average Grant Price Per Share
Nonvested at December 31, 2015		58,194		$	19.69
Granted		89,850		$	17.92
Vested		(29,898	)	$	17.86
Forfeited		(1,314	)	$	16.85

Nonvested at December 31, 2016		116,832		$	18.32
Granted		86,614		$	28.77
Vested		(86,788	)	$	18.64
Forfeited		—		$	—

Nonvested at December 31, 2017		116,658		$	25.85
Granted		80,570		$	35.26
Vested		(106,022	)	$	23.52
Forfeited		—		$	—

Nonvested at December 31, 2018		91,206		$	36.86

Stock Appreciation Rights

SARs are granted with a grant price equal to the closing market price of the Company’s common stock on the date of grant. These awards expire ten years after the date of grant and vest based on the terms of the individual awards. The SARs are generally forfeitable upon the resignation of employment or termination of employment with cause. The Company recognizes compensation cost on a straight-line basis over the vesting period for the award.

As of December 31, 2018, there was $0.4 million of unrecognized compensation cost related to SARs. The fair value of each SAR is estimated on the date of grant using a Black-Scholes option-pricing model. There were no SARs issued in the year ended December 31, 2016. For SARs issued in the years ended December 31, 2018 and December 31, 2017, respectively, the assumptions shown in the following table were used:


	December 31,
	2018			2017
Dividend yield		0	%		0	%
Average risk-free interest rate		2.7	%		2.0	%
Expected term (years)		5			5
Expected volatility		40.5	%		42.3	%

Dividend Yield. The Company has never paid cash dividends on its common stock.

Average Risk-Free Interest Rate. The Company uses the U.S. Treasury rate having a term that most closely resembles the expected term of the option.

Expected Term. The expected term is the period of time that the SARs granted are expected to remain unexercised. SARs granted during the years ended December 31, 2018 and 2017 had a maximum term of ten years. The Company used historical exercise behavior with further consideration given to the class of employees to whom the equity awards were granted to estimate the expected term of the SAR.

Expected Volatility. Volatility is a measure of the amount by which a financial variable such as a share price has fluctuated (historical volatility) or is expected to fluctuate (expected volatility) during a period. The Company has used the historical volatility over the average expected term of the options granted as the expected volatility.

The Company recognizes forfeitures as they occur.

The weighted-average grant date fair value of SARs granted during the years ended December 31, 2018 and December 31, 2017 was $22.09 and $13.99, respectively.

SAR activity under the Plan and all predecessor stock incentive plans is as follows:


	SARs			Weighted-Average Grant Price Per Share		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value as of December 31, 2018
Outstanding at December 31, 2015		524,154		$	6.57
Granted		—		$	—
Exercised		(248,704	)	$	5.55
Canceled		—		$	—

Outstanding at December 31, 2016		275,450		$	9.79
Granted		37,478		$	35.38
Exercised		(34,812	)	$	8.07
Canceled		—		$	—

Outstanding at December 31, 2017		278,116		$	13.45
Granted		21,260		$	56.59
Exercised		(60,900	)	$	5.27
Canceled		—		$	—

Outstanding at December 31, 2018		238,476		$	19.26		5.3	$	9,562,603
Vested at December 31, 2018		192,232		$	13.08		4.5	$	8,896,335
Exercisable at December 31, 2018		192,232		$	13.08		4.5	$	8,896,335

Employee Stock Purchase Plan

The Company has an employee stock purchase plan (ESPP) that permits eligible employees to purchase shares of common stock of the Company at a purchase price which is the lesser of 85% of the market price on either the first day of the calendar quarter or the last day of the calendar quarter. Eligible employees may elect to participate in the plan by authorizing payroll deductions of up to 15% of gross compensation for each payroll period. On the last day of each quarter, each participant’s contribution account is used to purchase the maximum number of whole shares of common stock determined by dividing the contribution account balance by the purchase price. The aggregate number of shares of common stock that may be purchased under the plan is 1,200,000. Through December 31, 2018, employees had purchased approximately 874,235 shares under the plan.

Leases

12 Months Ended

Dec. 31, 2018

Leases [Abstract]

Leases

14.

LEASES

The Company leases office space, storage warehouses and certain office and plant equipment under various operating leases. Minimum annual payments under these non-cancelable leases as of December 31, 2018 were as follows (in thousands):


Year Ending December 31,
2019	$	10,998
2020		9,317
2021		8,952
2022		6,901
2023		6,576
Thereafter		19,080

Total minimum lease payments	$	61,824

For the years ended December 31, 2018, 2017 and 2016, the Company recognized rental expenses of approximately $10.0 million, $9.1 million, and $9.9 million, respectively.

Employee Benefit Plans

12 Months Ended

Dec. 31, 2018

Postemployment Benefits [Abstract]

Employee Benefit Plans

15.

EMPLOYEE BENEFIT PLANS

The Company has two 401(k) Profit Sharing Plans for the benefit of its employees who meet certain eligibility requirements. The plans cover substantially all of the Company’s full-time employees. One of the plans provides for the Company to match contributions equal to 100% of an employee’s contribution to the plan up to 6% of base salary. The other plan provides for the Company to match $0.25 in 2018 and $0.50 beginning in 2019 for every $1.00 contributed by an employee to the plan up to 6% of compensation.

The Company’s contributions to the plans totaled $4.2 million, $3.0 million, and $2.5 million, for the years ended December 31, 2018, 2017 and 2016, respectively.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

16.

INCOME TAXES

Income tax provision (benefit) consists of the following (in thousands):


	Year Ended December 31,
	2018		2017			2016
Current income tax provision:
Federal	$	33,578	$	41,177		$	26,752
State		7,674		5,420			2,798

		41,252		46,597			29,550

Deferred income tax provision:
Federal		988		1,177			5,217
State		49		(983	)		216

		1,037		194			5,433

Total income tax provision	$	42,289	$	46,791		$	34,983

The income tax provision differs from the amount of income tax determined by applying the U.S. Federal statutory rate to income before taxes as a result of the following (in thousands):


	Year Ended December 31,
	2018			2017			2016
U.S. Federal statutory taxes	$	37,141		$	49,671		$	35,990
State and local taxes, net of U.S. Federal benefit		7,716			5,110			3,747
Permanent items		470			576			396
Excess tax benefits from vesting or settlement of stock compensation awards		(2,368	)		(1,454	)		(1,749	)
Domestic production activities deduction		—			(4,376	)		(2,740	)
Federal credits		(662	)		(534	)		(488	)
Other		(8	)		(2,202	)		(173	)

Total income tax provision	$	42,289		$	46,791		$	34,983

Deferred tax assets and liabilities consist of the following (in thousands):


	As of December 31,
	2018			2017
Deferred tax assets:
Net operating losses	$	79		$	123
Residential product warranty reserve		7,804			8,876
Stock-based compensation		1,725			1,823
Accruals not currently deductible and other		3,928			1,838
Inventories		4,682			3,783
State tax credit carryforwards		3,400			3,619

Gross deferred tax assets, before valuation allowance		21,618			20,062
Valuation allowance		(3,015	)		(3,096	)

Gross deferred tax assets, after valuation allowance		18,603			16,966

Deferred tax liabilities:
Depreciation		(13,893	)		(12,046	)
Goodwill amortization		(3,774	)		(2,781	)
Inventories and other		(3,061	)		(3,228	)

Gross deferred tax liabilities		(20,728	)		(18,055	)

Net deferred tax liability	$	(2,125	)	$	(1,089	)

The Company has recognized the tax effects of the Tax Cuts and Jobs Act (Act) in its consolidated financial statements and related notes as of and for the year ended December 31, 2017. Deferred tax assets and deferred tax liabilities that existed as of the enactment date and that reversed after the Act’s effective date of January 1, 2018 were adjusted to reflect the new Federal statutory tax rate of 21%. The effect of the change in tax rate on the deferred tax assets and deferred tax liabilities resulted in a tax benefit of $1.9 million for the year ended December 31, 2017, which is included in “Other” in the above tax rate reconciliation. The Company finalized its analysis of the Act and completed its calculation, which did not affect the measurement of these balances nor give rise to new deferred tax amounts. As of December 31, 2018, the Company had a valuation allowance of $3.0 million against deferred tax assets it estimates will not be realized. The Company will analyze its position in subsequent reporting periods, considering all available positive and negative evidence, in determining the expected realization of its deferred tax assets.

The Company realized $2.4 million and $1.5 million of excess tax benefits during 2018 and 2017, respectively, related to share-based compensation awards.

The Company recognizes interest and penalties related to tax matters as a component of “Selling, general and administrative expenses” in the accompanying Consolidated Statements of Comprehensive Income. As of December 31, 2018, the Company has identified no uncertain tax position and, accordingly, has not recorded any unrecognized tax benefits or associated interest and penalties.

The Company operates in multiple tax jurisdictions and, in the normal course of business, its tax returns are subject to examination by various taxing authorities. Such examinations may result in future assessments by these taxing authorities, and the Company has accrued a liability when it believes that it is not more likely than not that it will realize the benefits of tax positions that it has taken or for the amount of any tax benefit that exceeds the cumulative probability threshold in accordance with accounting standards. As of December 31, 2018, Federal tax years 2015 through 2018 remain subject to examination. The Company believes that adequate provisions have been made for all tax returns subject to examination. Sales made to foreign distributors are not taxable in any foreign jurisdictions as the Company does not have a taxable presence.

Segment Information

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Segment Information

17.

SEGMENT INFORMATION

Prior to July 31, 2017, the Company operated in one reportable segment. Subsequent to the acquisition of certain assets and assumption of certain liabilities of SC Company on July 31, 2017, the Company operates in two reportable segments:

•

Trex Residential manufactures wood-alternative decking and railing and related products marketed under the brand name Trex^®. The products are sold to its distributors and two national retailers who, in turn, sell primarily to the residential market, which includes replacement, remodeling and new construction related to outdoor living products. Trex Residential net sales were $613.2 million, $543.3 million, and $479.6 million in the years ended December 31, 2018, 2017, and 2016, respectively.

•

Trex Commercial designs, engineers, and markets modular and architectural railing and staging systems for commercial and multi-family market, including sports stadiums and performing arts venues. The segment’s products are sold through architects, specifiers, contractors, and others doing business within the segment’s commercial market. Trex Commercial net sales were $71.0 million in the year ended December 31, 2018, and $21.8 million from the date of acquisition through December 31, 2017.

The Company’s reportable segments have been determined in accordance with its internal management structure, which is organized based on residential and commercial operations. The Company evaluates performance of each segment primarily based on net sales and earnings before interest, taxes, depreciation and amortization (EBITDA). The Company uses net sales to assess performance and allocate resources as this measure represents the amount of business the segment engaged in during a given period of time, is an indicator of market growth and acceptance of segment products, and represents the segment’s customers’ spending habits along with the amount of product the segment sells relative to its competitors. The Company uses EBITDA to assess performance and allocate resources because it believes that EBITDA facilitates performance comparison between the segments by eliminating interest, taxes, and depreciation and amortization charges to income. The below segment data includes data for Trex Residential for the years ended December 31, 2018 and December 31, 2017, and data for Trex Commercial for the year ended December 31, 2018, and for the year ended December 31, 2017 from the date of the acquisition of SC Company through December 31, 2017 (in thousands):


	Year ended December 31, 2018
	Trex Residential		Trex Commercial		Total
Net sales	$	613,229	$	71,021	$	684,250
Net income	$	131,823	$	2,749	$	134,572
EBITDA	$	186,268	$	6,868	$	193,136
Depreciation and amortization	$	13,216	$	3,251	$	16,467
Income tax expense	$	41,421	$	868	$	42,289
Capital expenditures	$	31,392	$	2,424	$	33,816
Total assets	$	380,682	$	84,440	$	465,122

Reconciliation of net income to EBITDA:


	Year Ended December 31, 2018
	Trex Residential			Trex Commercial		Total
Net income	$	131,823		$	2,749	$	134,572
Interest (income) expense, net		(192	)		—		(192	)
Taxes		41,421			868		42,289
Depreciation and amortization		13,216			3,251		16,467

EBITDA	$	186,268		$	6,868	$	193,136


	Year ended December 31, 2017
	Trex Residential		Trex Commercial			Total
Net sales	$	543,346	$	21,807		$	565,153
Net income (loss)	$	97,412	$	(2,284	)	$	95,128
EBITDA	$	160,382	$	(1,272	)	$	159,110
Depreciation and amortization	$	14,598	$	2,132		$	16,730
Income tax expense (benefit)	$	47,911	$	(1,120	)	$	46,791
Capital expenditures	$	14,989	$	51		$	15,040
Total assets	$	247,817	$	78,410		$	326,227

Reconciliation of net income to EBITDA:


	Year Ended December 31, 2017
	Trex Residential		Trex Commercial			Total
Net income (loss)	$	97,412	$	(2,284	)	$	95,128
Interest		461		—			461
Taxes		47,911		(1,120	)		46,791
Depreciation and amortization		14,598		2,132			16,730

EBITDA	$	160,382	$	(1,272	)	$	159,110

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

19.

COMMITMENTS AND CONTINGENCIES

Legal Matters

The Company has lawsuits, as well as other claims, pending against it which are ordinary routine litigation and claims incidental to the business. Management has evaluated the merits of these lawsuits and claims, and believes that their ultimate resolution will not have a material effect on the Company’s consolidated financial condition, results of operations, liquidity or competitive position.

Purchase Commitments

The Company fulfills requirements for raw materials under both purchase orders and supply contracts. In the year ended December 31, 2018, the Company purchased substantially all of its reclaimed wood fiber requirements under purchase orders which do not involve long-term supply commitments. All of the Company’s scrap polyethylene, aluminum and stainless steel purchases are under short-term supply contracts that may average approximately one to two years, for which pricing is negotiated as needed, or under purchase orders that do not involve long-term supply commitments.

The wood and polyethylene supply contracts generally provide that the Company is obligated to purchase all of the wood or polyethylene a supplier provides, if the wood or polyethylene meets certain specifications. The amount of wood and polyethylene the Company is required to purchase under these contracts varies with the production of its suppliers and, accordingly, is not fixed or determinable. As of December 31, 2018, the Company has purchase commitments under material supply contracts of $19.0 million, $7.6 million, and $0.03 million for the years ending December 31, 2019, 2020, and 2021, respectively.

Product Warranty

The Company warrants that its Trex Residential products will be free from material defects in workmanship and materials. This warranty generally extends for a period of 25 years for residential use and 10 years for commercial use, excluding Trex Signature^® Railing, which has a warranty period of 25 years for both residential and commercial use. The Company further warrants that Trex Transcend^®, Trex Enhance^®, Trex Select^® and Universal Fascia products will not fade in color more than a certain amount and will be resistant to permanent staining from food substances or mold, provided the stain is cleaned within seven days of appearance. This warranty extends for a period of 25 years for residential use and 10 years for commercial use. If there is a breach of such warranties, the Company has an obligation either to replace the defective product or refund the purchase price. The Company also warrants its Trex Commercial products for one to three years.

The Company continues to receive and settle claims for decking products manufactured at its Nevada facility prior to 2007 that exhibit surface flaking and maintains a warranty reserve to provide for the settlement of these claims. Estimating the warranty reserve for surface flaking claims requires management to estimate (1) the number of claims to be settled with payment and (2) the average cost to settle each claim.

To estimate the number of claims to be settled with payment, the Company utilizes actuarial techniques to determine a reasonable possible range of claims to be received and the percentage of those claims that will ultimately require payment. Management utilizes a range of assumptions derived from claim count history and the identification of factors influencing the claim counts to determine its best estimate of future claims for which to record a related liability. The number of claims received has declined each year since peaking in 2009, although the rate of decline has decelerated in recent years. The cost per claim varies due to a number of factors, including the size of affected decks, the availability and type of replacement material used, the cost of production of replacement material and the method of claim settlement.

The Company monitors surface flaking claims activity each quarter for indications that its estimates require revision. Typically, a majority of surface flaking claims received in a year are received during the summer outdoor season, which spans the second and third quarters. It has been the Company’s practice to utilize the actuarial techniques discussed above during the third quarter, after a significant portion of all claims has been received for the fiscal year and variances to annual claims expectations are more meaningful. The number of incoming claims received in the year ended December 31, 2018, was lower than the Company’s expectations and considerably lower than the number of claims received in the year ended December 31, 2017, continuing the historical year-over-year decline in incoming claims. The favorable experience in incoming claims was offset, in part, by increased average settlement cost per claim experienced in the year ended December 31, 2018. The Company believes its reserve at December 31, 2018 is sufficient to cover future surface flaking obligations and no adjustments were required in the current year.

The Company’s analysis is based on currently known facts and a number of assumptions, as discussed above, and current expectations. Projecting future events such as the number of claims to be received, the number of claims that will require payment and the average cost of claims could cause the actual warranty liabilities to be higher or lower than those projected, which could materially affect the Company’s financial condition, results of operations or cash flows. The Company estimates that the annual number of claims received will continue to decline over time and that the average cost per claim will increase slightly, primarily due to inflation. If the level of claims received or average cost per claim differs materially from expectations, it could result in additional increases or decreases to the warranty reserve and a decrease or increase in earnings and cash flows in future periods. The Company estimates that a 10% change in the expected number of remaining claims to be settled with payment or the expected cost to settle claims may result in approximately a $2.6 million change in the surface flaking warranty reserve.

The Company also maintains a warranty reserve for the settlement of other residential product warranty claims and records the provision at the time of product sale.

The following is a reconciliation of the Company’s residential product warranty reserve (in thousands):


	Year Ended December 31, 2018
	Surfac eFlaking			Other Residential			Total
Beginning balance, January 1	$	28,158		$	6,841		$	34,999
Provisions and changes in estimates		—			1,104			1,104
Settlements made during the period		(4,207	)		(1,142	)		(5,349	)

Ending balance, December 31	$	23,951		$	6,803		$	30,754


	Year Ended December 31, 2017
	Surface Flaking			Other Residential			Total
Beginning balance, January 1	$	33,847		$	3,845		$	37,692
Provisions and changes in estimates		—			4,268			4,268
Settlements made during the period		(5,689	)		(1,272	)		(6,961	)

Ending balance, December 31	$	28,158		$	6,841		$	34,999

Interim Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Interim Financial Data (Unaudited)

20.

INTERIM FINANCIAL DATA (Unaudited)


	Three Months Ended
	December 31, 2018		September 30, 2018		June 30, 2018		March 31, 2018		December 31, 2017		September 30, 2017		June 30, 2017		March 31, 2017
	(In thousands, except share and per share data)
Net sales	$	139,971	$	166,380	$	206,692	$	171,207	$	122,212	$	140,194	$	157,941	$	144,806
Gross profit	$	59,856	$	67,210	$	91,115	$	76,713	$	50,906	$	55,284	$	72,014	$	65,169
Net income	$	25,171	$	29,471	$	42,820	$	37,110	$	18,299	$	20,098	$	28,782	$	27,949
Basic net income per share	$	0.43	$	0.50	$	0.73	$	0.63	$	0.31	$	0.34	$	0.49	$	0.48
Basic weighted average common shares outstanding		58,603,537		58,741,973		58,760,753		58,855,156		58,825,696		58,808,098		58,778,916		58,726,420
Diluted net income per share	$	0.43	$	0.50	$	0.73	$	0.63	$	0.31	$	0.34	$	0.49	$	0.48
Diluted weighted average common shares outstanding		58,936,795		59,084,117		59,051,413		59,199,622		59,222,258		59,156,432		59,100,836		59,122,812

The operating results for Trex Residential have historically varied from quarter to quarter. Seasonal, erratic or prolonged adverse weather conditions in certain geographic regions reduce the level of home improvement and construction activity and can shift demand for its products to a later period. The operating results for Trex Commercial have not historically varied from quarter to quarter as a result of seasonality; however, they are driven by the timing of individual projects, which may vary each quarterly period.

The Tax Cuts and Jobs Act (Act) was enacted on December 22, 2017. Accordingly, the Company has recognized the tax effects of the Act in its consolidated financial statements and related notes as of and for the year ended December 31, 2017. Deferred tax assets that existed as of the enactment date and that are expected to reverse after the Act’s effective date of January 1, 2018 have been adjusted to reflect the new Federal statutory tax rate of 21%. The effect of the change in tax rate on the deferred tax assets and deferred tax liabilities resulted in a tax benefit of $1.9 million for the year ended December 31, 2017.

On May 2, 2018, the Board of Directors of the Company approved a two-for-one stock split of the Company’s common stock, par value $0.01. The stock split was in the form of a stock dividend distributed on June 18, 2018, to stockholders of record at the close of business on May 23, 2018. The stock split entitled each stockholder to receive one additional share of common stock, par value $0.01, for each share they held as of the record date. All common stock share and per share data for all periods presented have been retroactively adjusted to reflect the stock split.

Schedule II - Valuation and Qualifying Accounts and Reserves

12 Months Ended

Dec. 31, 2018

SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]

Schedule II - Valuation and Qualifying Accounts and Reserves

TREX COMPANY, INC.

SCHEDULE II—VALUATION AND QUALIFYING ACCOUNTS AND RESERVES

(In thousands)


Descriptions	Balance at Beginning of Period		Additions (Reductions) Charged to Cost and Expenses		Deductions			Balance at End of Period
Year ended December 31, 2018:
Trex Residential product warranty reserve	$	34,999	$	1,104	$	(5,349	)	$	30,754

Income tax valuation allowance	$	3,096	$	—	$	(81	)	$	3,015

Year ended December 31, 2017:
Trex Residential product warranty reserve	$	37,692	$	4,268	$	(6,961	)	$	34,999

Income tax valuation allowance	$	4,061	$	—	$	(965	)	$	3,096

Year ended December 31, 2016:
Trex Residential product warranty reserve	$	33,522	$	10,852	$	(6,682	)	$	37,692

Income tax valuation allowance	$	4,582	$	—	$	(521	)	$	4,061

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Basis of Accounting

Basis of Accounting

Use of Estimates

Use of Estimates

Cash and Cash Equivalents

Cash and Cash Equivalents

Cash equivalents consist of highly liquid investments purchased with original maturities of three months or less.

Concentrations and Credit Risk

Concentrations and Credit Risk

For each year ended December 31, 2018, 2017 and 2016, approximately 33% of the Company’s materials purchases were purchased from its four largest suppliers.

Inventories

Inventories

Property, Plant and Equipment

Property, Plant and Equipment


Buildings		40 years
Machinery and equipment		3-11 years
Furniture and equipment		10 years
Forklifts and tractors		5 years
Computer equipment and software		5 years

Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset.

Fair Value Measurement

Fair Value Measurement

•

Level 1 – Quoted prices for identical instruments in active markets.

•

Goodwill

Product Warranty

Treasury Stock

Revenue Recognition

Trex Residential Products

Trex Commercial Products

Stock-Based Compensation

Stock-Based Compensation

Income Taxes

Income Taxes

Research and Development Costs

Research and Development Costs

Advertising Costs

Advertising Costs

For the years ended December 31, 2018, 2017 and 2016, branding expenses, including advertising expenses as described above, were $35.0 million, $31.0 million, and $24.8 million, respectively.

Fair Value of Financial Instruments

Fair Value of Financial Instruments

Recently Adopted Accounting Standards

Recently Adopted Accounting Standards

New Accounting Standards Not Yet Adopted

New Accounting Standards Not Yet Adopted

Acquisition (Tables)

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Summary of Consideration Allocated to Assets Acquired and Liabilities Assumed

Based on the Company’s valuation, total consideration of $71.8 million was allocated to the assets acquired and liabilities assumed, as follows (in thousands):


Accounts receivable, net	$	8,357
Contract retainage		1,948
Inventories, net		2,344
Prepaid expenses and other assets		1,223
Revenues in excess of billings		3,463
Fixed assets, net		1,264
Intangible assets		4,900
Goodwill		57,938
Accounts payable		(3,990	)
Accrued liabilities and other expenses		(2,329	)
Billings in excess of revenues		(1,752	)
Customer deposits		(1,562	)

Total consideration	$	71,804

Inventories (Tables)

12 Months Ended

Dec. 31, 2018

Inventory Disclosure [Abstract]

Summary of Inventories

Inventories (at LIFO value) consist of the following as of December 31 (in thousands):


	2018			2017
Finished goods	$	46,638		$	32,986
Raw materials		27,321			19,432

Total FIFO (first-in, first out) inventories		73,959			52,418
Reserve to adjust inventories to LIFO value		(18,442	)		(20,070	)

Total LIFO inventories	$	55,517		$	32,348

Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Details of Intangible Assets

Intangible assets consist of the following (in thousands):


	December 31, 2018			December 31, 2017
Intangible assets:
Customer backlog	$	4,000		$	4,000
Trade names and trademarks		900			900
Domain names		6,327			—

Total intangible assets		11,227			4,900

Accumulated amortization:
Customer backlog		(4,000	)		(1,666	)
Trade name and trademarks		(900	)		(376	)
Domain names		(285	)		—

Total accumulated amortization		(5,185	)		(2,042	)

Intantible assets, net	$	6,042		$	2,858

Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Summary of Property, Plant and Equipment

Property, plant and equipment consist of the following as of December 31 (in thousands):


	2018			2017
Building and improvements	$	50,240		$	49,403
Machinery and equipment		233,464			228,107
Furniture and fixtures		1,625			1,620
Forklifts and tractors		10,872			9,799
Computer equipment		10,142			9,680
Construction in process		16,392			5,954
Land		11,417			11,417

Total property, plant and equipment		334,152			315,980
Accumulated depreciation		(217,008	)		(212,870	)

Total property, plant and equipment, net	$	117,144		$	103,110

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Computation of Basic and Diluted Earnings Per Share

The following table sets forth the computation of basic and diluted earnings per share (in thousands, except share and per share data):


	Year Ended December 31,
	2018		2017		2016
Numerator:
Net income	$	134,572	$	95,128	$	67,847

Denominator:
Basic weighted average shares outstanding		58,739,670		58,785,118		58,789,118
Effect of dilutive securities:
Stock appreciation rights		176,700		198,642		250,238
Restricted stock		150,932		167,160		185,982

Diluted weighted average shares outstanding		59,067,302		59,150,920		59,225,338

Basic earnings per share	$	2.29	$	1.62	$	1.16

Diluted earnings per share	$	2.28	$	1.61	$	1.15

Antidilutive Securities Excluded from Computation of Earnings Per Share

effect of common stock equivalents using the treasury stock method. The computation of diluted earnings per share excludes the following potentially dilutive securities because the effect would be anti-dilutive:


	Year Ended December 31,
	2018		2017		2016
Restricted stock		214		166		24
Stock appreciation rights		13,347		21,234		9,262

Revenue From Contract With Customer (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Summary of Disaggregated Net Sales

The tables also include a reconciliation of the respective disaggregated net sales with the Company’s reportable segments (in thousands).


Year Ended December 31, 2018	Reportable Segment
	Trex Residential		Trex Commercial		*Total*
Timing of Revenue Recognition and Type of Contract
Products transferred at a point in time and variable consideration contracts	$	613.229	$	—	$	613,229
Products transferred over time and fixed price contracts		—		71,021		71,021

	$	613,229	$	71,021	$	684,250


Year Ended December 31, 2017	Reportable Segment
	Trex Residential		Trex Commercial		*Total*
Timing of Revenue Recognition and Type of Contract
Products transferred at a point in time and variable consideration contracts	$	543,346	$	—	$	543,346
Products transferred over time and fixed price contracts		—		21,807		21,807

	$	543,346	$	21,807	$	565,153

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Summary of Stock-Based Compensation Expense

The following table summarizes the Company’s stock-based compensation expense (in thousands):


	Year Ended December 31,
	2018		2017		2016
Time-based restricted stock and time-based restricted stock units	$	2,687	$	1,992	$	2,281
Performance-based restricted stock and performance-based restricted stock units		3,144		2,805		2,210
Stock appreciation rights		370		251		184
Employee stock purchase plan		143		139		113

Total stock-based compensation	$	6,344	$	5,187	$	4,788

Summary of Assumptions Used to Estimate Fair Value of Each SAR

For SARs issued in the years ended December 31, 2018 and December 31, 2017, respectively, the assumptions shown in the following table were used:


	December 31,
	2018			2017
Dividend yield		0	%		0	%
Average risk-free interest rate		2.7	%		2.0	%
Expected term (years)		5			5
Expected volatility		40.5	%		42.3	%

SAR Activity

SAR activity under the Plan and all predecessor stock incentive plans is as follows:


	SARs			Weighted-Average Grant Price Per Share		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value as of December 31, 2018
Outstanding at December 31, 2015		524,154		$	6.57
Granted		—		$	—
Exercised		(248,704	)	$	5.55
Canceled		—		$	—

Outstanding at December 31, 2016		275,450		$	9.79
Granted		37,478		$	35.38
Exercised		(34,812	)	$	8.07
Canceled		—		$	—

Outstanding at December 31, 2017		278,116		$	13.45
Granted		21,260		$	56.59
Exercised		(60,900	)	$	5.27
Canceled		—		$	—

Outstanding at December 31, 2018		238,476		$	19.26		5.3	$	9,562,603
Vested at December 31, 2018		192,232		$	13.08		4.5	$	8,896,335
Exercisable at December 31, 2018		192,232		$	13.08		4.5	$	8,896,335

Time-Based Restricted Stock and Time-Based Restricted Stock Units [Member]

Restricted Stock Activity

Time-based restricted stock and restricted stock unit activity under the Plan and all predecessor stock incentive plans is as follows:


	Time-based Restricted Stock and Restricted Stock Unit			Weighted-Average Grant Price Per Share
Nonvested at December 31, 2015		215,814		$	14.72
Granted		115,748		$	18.82
Vested		(87,696	)	$	21.17
Forfeited		(266	)	$	21.95

Nonvested at December 31, 2016		243,600		$	15.80
Granted		72,402		$	36.27
Vested		(162,372	)	$	14.45
Forfeited		(512	)	$	18.68

Nonvested at December 31, 2017		153,118		$	26.90
Granted		87,264		$	54.72
Vested		(84,550	)	$	26.65
Forfeited		(284	)	$	35.05

Nonvested at December 31, 2018		155,548		$	42.68

Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member]

Restricted Stock Activity

Performance-based restricted stock activity under the Plan is as follows:


	Performance-based Restricted Stock and Performance-based Restricted Stock Units			Weighted-Average Grant Price Per Share
Nonvested at December 31, 2015		58,194		$	19.69
Granted		89,850		$	17.92
Vested		(29,898	)	$	17.86
Forfeited		(1,314	)	$	16.85

Nonvested at December 31, 2016		116,832		$	18.32
Granted		86,614		$	28.77
Vested		(86,788	)	$	18.64
Forfeited		—		$	—

Nonvested at December 31, 2017		116,658		$	25.85
Granted		80,570		$	35.26
Vested		(106,022	)	$	23.52
Forfeited		—		$	—

Nonvested at December 31, 2018		91,206		$	36.86

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Tax Provision (Benefit)

Income tax provision (benefit) consists of the following (in thousands):


	Year Ended December 31,
	2018		2017			2016
Current income tax provision:
Federal	$	33,578	$	41,177		$	26,752
State		7,674		5,420			2,798

		41,252		46,597			29,550

Deferred income tax provision:
Federal		988		1,177			5,217
State		49		(983	)		216

		1,037		194			5,433

Total income tax provision	$	42,289	$	46,791		$	34,983

Reconciliation of Differences between Income Tax Provision and Income Tax Determined by Applying US Federal Statutory Rate

The income tax provision differs from the amount of income tax determined by applying the U.S. Federal statutory rate to income before taxes as a result of the following (in thousands):


	Year Ended December 31,
	2018			2017			2016
U.S. Federal statutory taxes	$	37,141		$	49,671		$	35,990
State and local taxes, net of U.S. Federal benefit		7,716			5,110			3,747
Permanent items		470			576			396
Excess tax benefits from vesting or settlement of stock compensation awards		(2,368	)		(1,454	)		(1,749	)
Domestic production activities deduction		—			(4,376	)		(2,740	)
Federal credits		(662	)		(534	)		(488	)
Other		(8	)		(2,202	)		(173	)

Total income tax provision	$	42,289		$	46,791		$	34,983

Schedule of Deferred Tax Assets and Liabilities

Deferred tax assets and liabilities consist of the following (in thousands):


	As of December 31,
	2018			2017
Deferred tax assets:
Net operating losses	$	79		$	123
Residential product warranty reserve		7,804			8,876
Stock-based compensation		1,725			1,823
Accruals not currently deductible and other		3,928			1,838
Inventories		4,682			3,783
State tax credit carryforwards		3,400			3,619

Gross deferred tax assets, before valuation allowance		21,618			20,062
Valuation allowance		(3,015	)		(3,096	)

Gross deferred tax assets, after valuation allowance		18,603			16,966

Deferred tax liabilities:
Depreciation		(13,893	)		(12,046	)
Goodwill amortization		(3,774	)		(2,781	)
Inventories and other		(3,061	)		(3,228	)

Gross deferred tax liabilities		(20,728	)		(18,055	)

Net deferred tax liability	$	(2,125	)	$	(1,089	)

Segment Information (Tables)

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Details of Segment Information

The below segment data includes data for Trex Residential for the years ended December 31, 2018 and December 31, 2017, and data for Trex Commercial for the year ended December 31, 2018, and for the year ended December 31, 2017 from the date of the acquisition of SC Company through December 31, 2017 (in thousands):


	Year ended December 31, 2018
	Trex Residential		Trex Commercial		Total
Net sales	$	613,229	$	71,021	$	684,250
Net income	$	131,823	$	2,749	$	134,572
EBITDA	$	186,268	$	6,868	$	193,136
Depreciation and amortization	$	13,216	$	3,251	$	16,467
Income tax expense	$	41,421	$	868	$	42,289
Capital expenditures	$	31,392	$	2,424	$	33,816
Total assets	$	380,682	$	84,440	$	465,122


	Year ended December 31, 2017
	Residential		Commercial			Total
Net sales	$	543,346	$	21,807		$	565,153
Net income (loss)	$	97,412	$	(2,284	)	$	95,128
EBITDA	$	160,382	$	(1,272	)	$	159,110
Depreciation and amortization	$	14,598	$	2,132		$	16,730
Income tax expense (benefit)	$	47,911	$	(1,120	)	$	46,791
Capital expenditures	$	14,989	$	51		$	15,040
Total assets	$	247,817	$	78,410		$	326,227

Schedule of Reconciliation of Net Income to EBITDA

Reconciliation of net income to EBITDA:


	Year Ended December 31, 2018
	Residential			Commercial		Total
Net income	$	131,823		$	2,749	$	134,572
Interest (income) expense, net		(192	)		—		(192	)
Taxes		41,421			868		42,289
Depreciation and amortization		13,216			3,251		16,467

EBITDA	$	186,268		$	6,868	$	193,136

Reconciliation of net income to EBITDA:


	Year Ended December 31, 2017
	Trex Residential		Trex Commercial			Total
Net income (loss)	$	97,412	$	(2,284	)	$	95,128
Interest		461		—			461
Taxes		47,911		(1,120	)		46,791
Depreciation and amortization		14,598		2,132			16,730

EBITDA	$	160,382	$	(1,272	)	$	159,110

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Summary of Reconciliation of Company's Residential Product Warranty Reserve

The following is a reconciliation of the Company’s residential product warranty reserve (in thousands):


	Year Ended December 31, 2018
	Surfac eFlaking			Other Residential			Total
Beginning balance, January 1	$	28,158		$	6,841		$	34,999
Provisions and changes in estimates		—			1,104			1,104
Settlements made during the period		(4,207	)		(1,142	)		(5,349	)

Ending balance, December 31	$	23,951		$	6,803		$	30,754


	Year Ended December 31, 2017
	Surface Flaking			Other Residential			Total
Beginning balance, January 1	$	33,847		$	3,845		$	37,692
Provisions and changes in estimates		—			4,268			4,268
Settlements made during the period		(5,689	)		(1,272	)		(6,961	)

Ending balance, December 31	$	28,158		$	6,841		$	34,999

Interim Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Summary of Interim Financial Data


	Three Months Ended
	December 31, 2018		September 30, 2018		June 30, 2018		March 31, 2018		December 31, 2017		September 30, 2017		June 30, 2017		March 31, 2017
	(In thousands, except share and per share data)
Net sales	$	139,971	$	166,380	$	206,692	$	171,207	$	122,212	$	140,194	$	157,941	$	144,806
Gross profit	$	59,856	$	67,210	$	91,115	$	76,713	$	50,906	$	55,284	$	72,014	$	65,169
Net income	$	25,171	$	29,471	$	42,820	$	37,110	$	18,299	$	20,098	$	28,782	$	27,949
Basic net income per share	$	0.43	$	0.50	$	0.73	$	0.63	$	0.31	$	0.34	$	0.49	$	0.48
Basic weighted average common shares outstanding		58,603,537		58,741,973		58,760,753		58,855,156		58,825,696		58,808,098		58,778,916		58,726,420
Diluted net income per share	$	0.43	$	0.50	$	0.73	$	0.63	$	0.31	$	0.34	$	0.49	$	0.48
Diluted weighted average common shares outstanding		58,936,795		59,084,117		59,051,413		59,199,622		59,222,258		59,156,432		59,100,836		59,122,812

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018 USD ($) Customer Institution Supplier	Dec. 31, 2017 USD ($) Customer	Dec. 31, 2016 USD ($) Customer
Schedule Of Significant Accounting Policies [Line Items]
Charge to earning to fully reserve the equity investment and note	$ 2,400,000
Maximum term of original maturities to classify as cash equivalent	3 months
Number of financial institutions where deposits are maintained \| Institution	1
Valuation allowance	$ 0	$ 0
Number of customers that accounted for 10% or more of net sales \| Customer	2	2	2
Number of customer accounted for 10% or more account receivable \| Customer	4
Number of largest raw material suppliers \| Supplier	4
Excess of the replacement cost of inventory over the LIFO value of inventory	$ (18,442,000)	$ (20,070,000)
Annual impairment test of goodwill	0	0	$ 0
Goodwill	68,500,000
Impairment loss on contract	0
Valuation allowance	3,015,000	3,096,000
Research and Development costs	4,200,000	3,800,000	3,700,000
Prepaid expenses for production costs of advertising	0	3,800,000	2,400,000
Branding Expenses	$ 35,000,000	$ 31,000,000	$ 24,800,000
Residential Use [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	25 years
Commercial Use [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	10 years
Trex Signature Railing [Member] \| Residential Use [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	25 years
Trex Signature Railing [Member] \| Commercial Use [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	25 years
Transcend, Enhance, Select and Universal Fascia Product [Member] \| Residential Use [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	25 years
Transcend, Enhance, Select and Universal Fascia Product [Member] \| Commercial Use [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	10 years
Commercial Railing and Staging Systems [Member] \| Commercial Use [Member] \| Minimum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	1 year
Commercial Railing and Staging Systems [Member] \| Commercial Use [Member] \| Maximum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	3 years
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member] \| Minimum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	10.00%	10.00%	10.00%
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member] \| Customer One [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	42.00%	41.00%	39.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer One [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	31.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Two [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	19.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Three [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	13.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Four [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	12.00%
Raw Materials [Member] \| Supplier Concentration Risk [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	33.00%	33.00%	33.00%
Denplax [Member]
Schedule Of Significant Accounting Policies [Line Items]
Holding company's interest in Denplax	35.00%

Summary of Significant Accounting Policies - Estimated Useful Lives of Property Plant and Equipment (Detail)	12 Months Ended
	Dec. 31, 2018
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment estimated useful life	40 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment estimated useful life	10 years
Forklifts and Tractors [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment estimated useful life	5 years
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment estimated useful life	5 years
Minimum [Member] \| Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment estimated useful life	3 years
Maximum [Member] \| Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment estimated useful life	11 years

Acquisition - Additional Information (Detail) - USD ($)			3 Months Ended								5 Months Ended	12 Months Ended
Acquisition - Additional Information (Detail) - USD ($)	Aug. 17, 2017	Jul. 31, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Repayment of revolving credit facility												$ 172,250,000	$ 201,000,000	$ 249,700,000
Goodwill			$ 68,500,000									68,500,000
Net income (loss)			25,171,000	$ 29,471,000	$ 42,820,000	$ 37,110,000	$ 18,299,000	$ 20,098,000	$ 28,782,000	$ 27,949,000		134,572,000	95,128,000	$ 67,847,000
Amortization expense												3,100,000	2,000,000
Acquisition-related expenses											$ 500,000
Trex Commercial Products, Inc. (TCP) [Member]
Business Acquisition [Line Items]
Net sales											21,800,000	71,000,000
Net income (loss)											(2,300)	2,700,000
Amortization expense											2,000,000	2,900,000
Staging Concepts Acquisition, LLC [Member]
Business Acquisition [Line Items]
Certain assets and liabilities acquired		$ 71,800,000
Total consideration		71,804,000
Goodwill		57,938,000
Goodwill expected to be amortized and deductible for tax purposes			$ 3,900,000				$ 1,600,000				$ 1,600,000	$ 3,900,000	$ 1,600,000
Amortization period for intangible assets												12 months
Staging Concepts Acquisition, LLC [Member] \| Revolving Credit Facility [Member]
Business Acquisition [Line Items]
Fund used to acquire business from revolving credit facility		$ 30,000,000
Repayment of revolving credit facility	$ 30,000,000

Acquisition - Summary of Consideration Allocated to Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jul. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 68,500
Staging Concepts Acquisition, LLC [Member]
Business Acquisition [Line Items]
Accounts receivable, net		$ 8,357
Contract retainage		1,948
Inventories, net		2,344
Prepaid expenses and other assets		1,223
Revenues in excess of billings		3,463
Fixed assets, net		1,264
Intangible assets		4,900
Goodwill		57,938
Accounts payable		(3,990)
Accrued liabilities and other expenses		(2,329)
Billings in excess of revenues		(1,752)
Customer deposits		(1,562)
Total consideration		$ 71,804

Inventories - Summary of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Finished goods	$ 46,638	$ 32,986
Raw materials	27,321	19,432
Total FIFO (first-in, first out) inventories	73,959	52,418
Reserve to adjust inventories to LIFO value	(18,442)	(20,070)
Total LIFO inventories	$ 55,517	$ 32,348

Prepaid Expenses and Other Assets - Summary of Prepaid Expenses and Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Prepaid Expense and Other Assets [Abstract]
Revenues in excess of billings	$ 7,987	$ 4,841
Prepaid expenses	3,390	7,494
Contract retainage	2,469	1,449
Income tax receivable	471	2,230
Other	1,245	864
Total prepaid expenses and other assets	$ 15,562	$ 16,878

Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill		$ 68.5
Amortization of intangible asset		3.1	$ 2.0
Commercial [Member]
Goodwill [Line Items]
Goodwill		54.3
Residential [Member]
Goodwill [Line Items]
Goodwill		$ 14.2
Domain Names [Member]
Goodwill [Line Items]
Amortization period		15 years
Purchase of domain names	$ 6.3
Customer Backlog [Member]
Goodwill [Line Items]
Amortization period		12 months
Trade Names and Trademarks [Member]
Goodwill [Line Items]
Amortization period		12 months

Goodwill and Other Intangible Assets - Details of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Indefinite-lived Intangible Assets [Line Items]
Total intangible assets	$ 11,227	$ 4,900
Total accumulated amortization	(5,185)	(2,042)
Intangible assets, net	6,042	2,858
Domain Names [Member]
Indefinite-lived Intangible Assets [Line Items]
Total intangible assets	6,327
Total accumulated amortization	(285)
Customer Backlog [Member]
Indefinite-lived Intangible Assets [Line Items]
Total intangible assets	4,000	4,000
Total accumulated amortization	(4,000)	(1,666)
Trade Names and Trademarks [Member]
Indefinite-lived Intangible Assets [Line Items]
Total intangible assets	900	900
Total accumulated amortization	$ (900)	$ (376)

Property, Plant and Equipment - Summary of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 334,152	$ 315,980
Accumulated depreciation	(217,008)	(212,870)
Total property, plant and equipment, net	117,144	103,110
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	50,240	49,403
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	233,464	228,107
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,625	1,620
Forklifts and Tractors [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	10,872	9,799
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	10,142	9,680
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	16,392	5,954
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 11,417	$ 11,417

Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 334,152	$ 315,980
Depreciation expense	13,400	14,700	$ 14,200
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 16,392	$ 5,954

Accrued Expenses and Other Liabilities - Summary of Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Sales and marketing costs	$ 25,379	$ 21,964
Compensation and benefits	19,124	14,818
Manufacturing costs	3,744	1,979
Customer deposits	2,058	1,230
Rent obligations	663	779
Billings in excess of revenues	512	1,842
Other	4,811	3,654
Total accrued expenses	$ 56,291	$ 46,266	$ 46,266

Debt - Additional Information (Detail)		3 Months Ended	12 Months Ended
Debt - Additional Information (Detail)	Jan. 12, 2016	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017
Line of Credit Facility [Line Items]
Company indebtedness		$ 0	$ 0
Remaining available borrowing capacity		200,000,000	$ 200,000,000
Third Amended and Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Termination date of the Credit Agreement			Jan. 12, 2021
Third Amended and Restated Credit Agreement [Member] \| Federal Funds Rate [Member]
Line of Credit Facility [Line Items]
Interest rate	0.50%
Third Amended and Restated Credit Agreement [Member] \| Eurodollar Rate Loans [Member]
Line of Credit Facility [Line Items]
Interest rate	1.00%
Second Amended and Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Credit facility covenant terms				The material financial covenants and restrictions do not permit the Company’s fixed charge coverage ratio to be less than 1.5 to 1.0 and do not permit the Company’s consolidated debt to consolidated EBITDA ratio to exceed 3.0 to 1.0, measured as of the end of each fiscal quarter (and in the case of Consolidated EBITDA, for the four-quarter period ending on such date).
Revolver Loans Portion Effective January 1 through June 30 [Member] \| Third Amended and Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount		250,000,000	$ 250,000,000
Revolver Loans Portion Effective July 1 through December 31 [Member] \| Third Amended and Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount		$ 200,000,000	200,000,000
Revolving Credit Facility [Member] \| Second Amended and Restated Credit Agreement [Member] \| Minimum [Member]
Line of Credit Facility [Line Items]
Fixed charge coverage ratio as per credit agreement		1.5
Revolving Credit Facility [Member] \| Second Amended and Restated Credit Agreement [Member] \| Maximum [Member]
Line of Credit Facility [Line Items]
Consolidated debt to earnings before interest taxes depreciation amortization ratio as per the credit agreement		3.0
Revolving Credit Facility [Member] \| Letter of Credit Facility Sublimit [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount		$ 15,000,000	15,000,000
Revolving Credit Facility [Member] \| Swing Advance Loan Sublimit [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount		$ 5,000,000	$ 5,000,000

Stockholders' Equity - Additional Information (Detail) $ / shares in Units, $ in Millions		12 Months Ended
	May 02, 2018 shares	Dec. 31, 2018 $ / shares shares	Dec. 31, 2016 USD ($) shares	Feb. 16, 2018 shares	Dec. 31, 2017 shares	Feb. 16, 2017 shares	Oct. 22, 2015 shares
Equity, Class of Treasury Stock [Line Items]
Common stock, par value \| $ / shares		$ 0.01
Common stock, shares authorized	80,000,000	120,000,000			120,000,000
Stock split	2
October 2014 Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase program, termination date		Oct. 22, 2015
October 2015 Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase program, termination date		Dec. 31, 2016
Common stock repurchase program, authorized shares							3,150,000
Number of shares repurchased by the Company			1,578,952
Value of shares repurchased by the Company \| $			$ 53.3
February 2017 Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase program, authorized shares						2,961,000
Number of shares repurchased by the Company		0
February 2018 Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase program, authorized shares				5,800,000
Number of shares repurchased by the Company		459,321

Stockholders' Equity - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income	$ 25,171	$ 29,471	$ 42,820	$ 37,110	$ 18,299	$ 20,098	$ 28,782	$ 27,949	$ 134,572	$ 95,128	$ 67,847
Denominator:
Basic weighted average shares outstanding	58,603,537	58,741,973	58,760,753	58,855,156	58,825,696	58,808,098	58,778,916	58,726,420	58,739,670	58,785,118	58,789,118
Effect of dilutive securities:
Diluted weighted average shares outstanding	58,936,795	59,084,117	59,051,413	59,199,622	59,222,258	59,156,432	59,100,836	59,122,812	59,067,302	59,150,920	59,225,338
Basic earnings per share	$ 0.43	$ 0.50	$ 0.73	$ 0.63	$ 0.31	$ 0.34	$ 0.49	$ 0.48	$ 2.29	$ 1.62	$ 1.16
Diluted earnings per share	$ 0.43	$ 0.50	$ 0.73	$ 0.63	$ 0.31	$ 0.34	$ 0.49	$ 0.48	$ 2.28	$ 1.61	$ 1.15
Stock Appreciation Rights [Member]
Effect of dilutive securities:
Dilutive securities									176,700	198,642	250,238
Restricted Stock [Member]
Effect of dilutive securities:
Dilutive securities									150,932	167,160	185,982

Stockholders' Equity - Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted earnings per share	214	166	24
Stock Appreciation Rights [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted earnings per share	13,347	21,234	9,262

Revenue From Contracts With Customers - Summary of Disaggregated Net Sales (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	$ 139,971,000	$ 166,380,000	$ 206,692,000	$ 171,207,000	$ 122,212,000	$ 140,194,000	$ 157,941,000	$ 144,806,000	$ 684,250,000	$ 565,153,000	$ 479,616,000
Products Transferred at a Point in Time and Variable Consideration Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									613,229,000	543,346,000
Products Transferred Over Time and Fixed Price Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									71,021,000	21,807,000
Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									613,229,000	543,346,000	$ 479,600
Residential [Member] \| Products Transferred at a Point in Time and Variable Consideration Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									613,229,000	543,346,000
Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									71,021,000	21,807,000
Commercial [Member] \| Products Transferred Over Time and Fixed Price Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									$ 71,021,000	$ 21,807,000

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Approximate number of shares employees purchased under the Employee Stock Purchase Plan		874,235
2014 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total aggregate number of shares of common stock that may be issued	12,840,000	12,840,000
Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost recognition period for unvested awards	1 year 6 months
Unrecognized compensation cost related to unvested awards	$ 1.6	$ 1.6	$ 1.8	$ 1.2
Vesting period		3 years
Number of shares or rights issued		80,570	86,614	89,850
Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] \| Share-Based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based Compensation vesting percentage		33.33%
Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] \| Share-Based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based Compensation vesting percentage		33.33%
Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] \| Share-Based Compensation Award, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based Compensation vesting percentage		33.33%
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested awards	0.4	$ 0.4
Maximum contractual term		10 years
Fair value assumptions method used		Black-Scholes option-pricing model
Number of shares or rights issued				0
Weighted-average fair value of grants		$ 22.09	$ 13.99
Time-Based Restricted Stock and Time-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost recognition period for unvested awards		2 years 8 months 12 days
Unrecognized compensation cost related to unvested awards	$ 5.1	$ 5.1
Total fair value of restricted shares vested		$ 4.2	$ 5.5	$ 1.7
Number of shares or rights issued		87,264	72,402	115,748
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total aggregate number of shares of common stock that may be issued	1,200,000	1,200,000
Percentage of market price on lesser of either first day of calendar quarter or last day of calendar quarter for purchase price		85.00%
Percentage of gross compensation eligible employees may elect to participate in the plan	15.00%	15.00%
Minimum [Member] \| Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target number of shares that will vest		0.00%
Maximum [Member] \| Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of target number of shares that will vest		200.00%

Stock-Based Compensation - Summary of Stock-Based Compensation Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6,344	$ 5,187	$ 4,788
Time-Based Restricted Stock and Time-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2,687	1,992	2,281
Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	3,144	2,805	2,210
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	370	251	184
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 143	$ 139	$ 113

Stock-Based Compensation - Time-Based Restricted Stock and Restricted Stock Unit Activity (Detail) - Time-Based Restricted Stock and Time-Based Restricted Stock Units [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Restricted Stock Activity [Line Items]
Nonvested, Shares, Beginning Balance	153,118	243,600	215,814
Time-based Restricted Stock, Granted	87,264	72,402	115,748
Time-based Restricted Stock, Vested	(84,550)	(162,372)	(87,696)
Time-based Restricted Stock, Forfeited	(284)	(512)	(266)
Nonvested, Shares, Ending Balance	155,548	153,118	243,600
Nonvested, Weighted-Average Grant Price Per Share, Beginning Balance	$ 26.90	$ 15.80	$ 14.72
Weighted-Average Grant Price Per Share, Granted	54.72	36.27	18.82
Weighted-Average Grant Price Per Share, Vested	26.65	14.45	21.17
Weighted-Average Grant Price Per Share, Forfeited	35.05	18.68	21.95
Nonvested, Weighted-Average Grant Price Per Share, Ending Balance	$ 42.68	$ 26.90	$ 15.80

Stock-Based Compensation - Performance-Based Restricted Stock Activity (Detail) - Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Restricted Stock Activity [Line Items]
Nonvested, Shares, Beginning Balance	116,658	116,832	58,194
Performance-based Restricted Stock, Granted	80,570	86,614	89,850
Performance-based Restricted Stock, Vested	(106,022)	(86,788)	(29,898)
Performance-based Restricted Stock, Forfeited			(1,314)
Nonvested, Shares, Ending Balance	91,206	116,658	116,832
Nonvested, Weighted-Average Grant Price Per Share, Beginning Balance	$ 25.85	$ 18.32	$ 19.69
Weighted-Average Grant Price Per Share, Granted	35.26	28.77	17.92
Weighted-Average Grant Price Per Share, Vested	23.52	18.64	17.86
Weighted-Average Grant Price Per Share, Forfeited			16.85
Nonvested, Weighted-Average Grant Price Per Share, Ending Balance	$ 36.86	$ 25.85	$ 18.32

Stock-Based Compensation - Summary of Assumptions Used to Estimate Fair Value of Each SAR (Detail) - Stock Appreciation Rights [Member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions and Methodology [Line Items]
Dividend yield	0.00%	0.00%
Average risk-free interest rate	2.70%	2.00%
Expected term (years)	5 years	5 years
Expected volatility	40.50%	42.30%

Stock-Based Compensation - SAR Activity (Detail) - Stock Appreciation Rights [Member] - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Stock Appreciation Rights Activity [Line Items]
SARs Outstanding, Beginning Balance	278,116	275,450	524,154
Granted, SARs	21,260	37,478
Exercised, SARs	(60,900)	(34,812)	(248,704)
Canceled, SARs	0	0	0
Shares Outstanding, SARs, Ending Balance	238,476	278,116	275,450
Outstanding, Weighted Average Grant Price Per Share, Beginning Balance	$ 13.45	$ 9.79	$ 6.57
Vested, SARs	192,232
Granted, Weighted Average Grant Price Per Share	$ 56.59	35.38
Exercisable, SARs	192,232
Exercised, Weighted Average Grant Price Per Share	$ 5.27	8.07	5.55
Canceled, Weighted Average Grant Price Per Share	0	0	0
Outstanding, Weighted Average Grant Price Per Share, Ending Balance	19.26	$ 13.45	$ 9.79
Vested, Weighted Average Grant Price Per Share	13.08
Exercisable, Weighted Average Grant Price Per Share	$ 13.08
Weighted Average Remaining Contractual Life, Outstanding	5 years 3 months 18 days
Weighted Average Remaining Contractual Life, Vested	4 years 6 months
Weighted Average Remaining Contractual Life, Exercisable	4 years 6 months
Aggregate Intrinsic Value, Outstanding	$ 9,562,603
Aggregate Intrinsic Value, Vested	8,896,335
Aggregate Intrinsic Value, Exercisable	$ 8,896,335

Leases - Minimum Annual Payments Under Non-Cancelable Leases (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	$ 10,998
2020	9,317
2021	8,952
2022	6,901
2023	6,576
Thereafter	19,080
Total minimum lease payments	$ 61,824

Employee Benefit Plans - Additional Information (Detail) - USD ($)		12 Months Ended
	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Percentage of employee's contribution to the plan up to 6% of base salary matched by the Company		100.00%
Employer's contribution percentage		6.00%
Employer's contribution		$ 4,200,000	$ 3,000,000	$ 2,500,000
401(k) Profit Sharing Plan Two [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer's contribution percentage		6.00%
Employer contribution to the plan for every $1.00 contributed by an employee		$ 0.25
Employee's contribution to the plan up to 6% of base salary by the company		$ 1.00
401(k) Profit Sharing Plan Two [Member] \| Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contribution to the plan for every $1.00 contributed by an employee	$ 0.50

Income Taxes - Income Tax Provision (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current income tax provision:
Federal	$ 33,578	$ 41,177	$ 26,752
State	7,674	5,420	2,798
Total	41,252	46,597	29,550
Deferred income tax provision:
Federal	988	1,177	5,217
State	49	(983)	216
Total	1,037	194	5,433
Total income tax provision	$ 42,289	$ 46,791	$ 34,983

Income Taxes - Reconciliation of Differences between Income Tax Provision and Income Tax Determined by Applying US Federal Statutory Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
U.S. Federal statutory taxes	$ 37,141	$ 49,671	$ 35,990
State and local taxes, net of U.S. Federal benefit	7,716	5,110	3,747
Permanent items	470	576	396
Excess tax benefits from vesting or settlement of stock compensation awards	(2,368)	(1,454)	(1,749)
Domestic production activities deduction		(4,376)	(2,740)
Federal credits	(662)	(534)	(488)
Other	(8)	(2,202)	(173)
Total income tax provision	$ 42,289	$ 46,791	$ 34,983

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating losses	$ 79	$ 123
Residential product warranty reserve	7,804	8,876
Stock-based compensation	1,725	1,823
Accruals not currently deductible and other	3,928	1,838
Inventories	4,682	3,783
State tax credit carryforwards	3,400	3,619
Gross deferred tax assets, before valuation allowance	21,618	20,062
Valuation allowance	(3,015)	(3,096)
Gross deferred tax assets, after valuation allowance	18,603	16,966
Deferred tax liabilities:
Depreciation	(13,893)	(12,046)
Goodwill amortization	(3,774)	(2,781)
Inventories and other	(3,061)	(3,228)
Gross deferred tax liabilities	(20,728)	(18,055)
Net deferred tax liability	$ (2,125)	$ (1,089)

Income Taxes - Additional Information (Detail)	12 Months Ended
Income Taxes - Additional Information (Detail)	Dec. 31, 2018 USD ($) Tax_Positions	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Income Tax Contingency [Line Items]
Statutory tax rate, percentage	21.00%
Deferred tax assets, liability		$ 1,900,000
Valuation allowance	$ 3,015,000	3,096,000
Income tax expense (benefit)	$ 42,289,000	46,791,000	$ 34,983,000
Unrecognized tax benefits number of tax matters \| Tax_Positions	0
Unrecognized tax benefits related to identified uncertain tax positions	$ 0
Tax years subject to examination	2015 2016 2017 2018
Accounting Standards Update 2016-09 [Member]
Income Tax Contingency [Line Items]
Income tax expense (benefit)	$ 2,400,000	$ 1,500,000

Segment Information - Additional Information (Detail)	3 Months Ended								7 Months Ended	12 Months Ended
Segment Information - Additional Information (Detail)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Jul. 31, 2017 Segment	Dec. 31, 2018 USD ($) Segment Retailer	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segment \| Segment									1	2
Net sales	$ 139,971,000	$ 166,380,000	$ 206,692,000	$ 171,207,000	$ 122,212,000	$ 140,194,000	$ 157,941,000	$ 144,806,000		$ 684,250,000	$ 565,153,000	$ 479,616,000
Number of national retailers \| Retailer										2
Residential [Member]
Segment Reporting Information [Line Items]
Net sales										$ 613,229,000	543,346,000	$ 479,600
Commercial [Member]
Segment Reporting Information [Line Items]
Net sales										$ 71,021,000	$ 21,807,000

Segment Information - Details of Segment Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 139,971,000	$ 166,380,000	$ 206,692,000	$ 171,207,000	$ 122,212,000	$ 140,194,000	$ 157,941,000	$ 144,806,000	$ 684,250,000	$ 565,153,000	$ 479,616,000
Net income (loss)	25,171,000	$ 29,471,000	$ 42,820,000	$ 37,110,000	18,299,000	$ 20,098,000	$ 28,782,000	$ 27,949,000	134,572,000	95,128,000	67,847,000
Depreciation and amortization									16,597,000	16,860,000	14,498,000
Income tax expense (benefit)									42,289,000	46,791,000	34,983,000
Total assets	465,122,000				326,227,000				465,122,000	326,227,000
Residential [Member]
Segment Reporting Information [Line Items]
Net sales									613,229,000	543,346,000	$ 479,600
Commercial [Member]
Segment Reporting Information [Line Items]
Net sales									71,021,000	21,807,000
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									684,250,000	565,153,000
Net income (loss)									134,572,000	95,128,000
EBITDA									193,136,000	159,110,000
Depreciation and amortization									16,467,000	16,730,000
Income tax expense (benefit)									42,289,000	46,791,000
Capital expenditures									33,816,000	15,040,000
Total assets	465,122,000				326,227,000				465,122,000	326,227,000
Operating Segments [Member] \| Residential [Member]
Segment Reporting Information [Line Items]
Net sales									613,229,000	543,346,000
Net income (loss)									131,823,000	97,412,000
EBITDA									186,268,000	160,382,000
Depreciation and amortization									13,216,000	14,598,000
Income tax expense (benefit)									41,421,000	47,911,000
Capital expenditures									31,392,000	14,989,000
Total assets	380,682,000				247,817,000				380,682,000	247,817,000
Operating Segments [Member] \| Commercial [Member]
Segment Reporting Information [Line Items]
Net sales									71,021,000	21,807,000
Net income (loss)									2,749,000	(2,284,000)
EBITDA									6,868,000	(1,272,000)
Depreciation and amortization									3,251,000	2,132,000
Income tax expense (benefit)									868,000	(1,120,000)
Capital expenditures									2,424,000	51,000
Total assets	$ 84,440,000				$ 78,410,000				$ 84,440,000	$ 78,410,000

Segment Information - Schedule of Reconciliation of Net Income to EBITDA (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net income (loss)	$ 25,171	$ 29,471	$ 42,820	$ 37,110	$ 18,299	$ 20,098	$ 28,782	$ 27,949	$ 134,572	$ 95,128	$ 67,847
Interest (income) expense, net									192	(461)	(1,125)
Taxes									42,289	46,791	34,983
Depreciation and amortization									16,597	16,860	$ 14,498
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net income (loss)									134,572	95,128
Interest (income) expense, net									(192)	461
Taxes									42,289	46,791
Depreciation and amortization									16,467	16,730
EBITDA									193,136	159,110
Operating Segments [Member] \| Residential [Member]
Segment Reporting Information [Line Items]
Net income (loss)									131,823	97,412
Interest (income) expense, net									(192)	461
Taxes									41,421	47,911
Depreciation and amortization									13,216	14,598
EBITDA									186,268	160,382
Operating Segments [Member] \| Commercial [Member]
Segment Reporting Information [Line Items]
Net income (loss)									2,749	(2,284)
Taxes									868	(1,120)
Depreciation and amortization									3,251	2,132
EBITDA									$ 6,868	$ (1,272)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Schedule Of Commitments And Contingencies [Line Items]
Change in warranty reserve for disclosure purposes only	$ 2,600
Minimum [Member]
Schedule Of Commitments And Contingencies [Line Items]
Average period for PE material purchases under short-term supply contracts for which pricing is negotiated as needed	1 year
Maximum [Member]
Schedule Of Commitments And Contingencies [Line Items]
Average period for PE material purchases under short-term supply contracts for which pricing is negotiated as needed	2 years
Surface Flaking Warranty Reserve [Member]
Schedule Of Commitments And Contingencies [Line Items]
Percentage change in warranty claims used as a threshold for disclosure	10.00%
Residential Use [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	25 years
Commercial Use [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	10 years
Transcend, Enhance, Select and Universal Fascia Product [Member] \| Residential Use [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	25 years
Transcend, Enhance, Select and Universal Fascia Product [Member] \| Commercial Use [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	10 years
Trex Signature Railing [Member] \| Residential Use [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	25 years
Trex Signature Railing [Member] \| Commercial Use [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	25 years
Commercial Railing and Staging Systems [Member] \| Commercial Use [Member] \| Minimum [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	1 year
Commercial Railing and Staging Systems [Member] \| Commercial Use [Member] \| Maximum [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	3 years
Raw Material Supply Contracts [Member]
Schedule Of Commitments And Contingencies [Line Items]
Purchase commitment	$ 19,000
Purchase commitment, due in second year	7,600
Purchase commitment, due in third year	$ 30

Commitments and Contingencies - Summary of Reconciliation of Company's Residential Product Warranty Reserve (Detail) - Surface Flaking Warranty Reserve [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Product Warranty Liability [Line Items]
Beginning balance	$ 34,999	$ 37,692
Provisions and changes in estimates	1,104	4,268
Settlements made during the period	(5,349)	(6,961)
Ending balance	30,754	34,999
Surface Flaking [Member]
Product Warranty Liability [Line Items]
Beginning balance	28,158	33,847
Settlements made during the period	(4,207)	(5,689)
Ending balance	23,951	28,158
Other Residential [Member]
Product Warranty Liability [Line Items]
Beginning balance	6,841	3,845
Provisions and changes in estimates	1,104	4,268
Settlements made during the period	(1,142)	(1,272)
Ending balance	$ 6,803	$ 6,841

Interim Financial Data (Unaudited) - Summary of Interim Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Net sales	$ 139,971	$ 166,380	$ 206,692	$ 171,207	$ 122,212	$ 140,194	$ 157,941	$ 144,806	$ 684,250	$ 565,153	$ 479,616
Gross profit	59,856	67,210	91,115	76,713	50,906	55,284	72,014	65,169	294,894	243,373	187,095
Net income	$ 25,171	$ 29,471	$ 42,820	$ 37,110	$ 18,299	$ 20,098	$ 28,782	$ 27,949	$ 134,572	$ 95,128	$ 67,847
Basic net income per share	$ 0.43	$ 0.50	$ 0.73	$ 0.63	$ 0.31	$ 0.34	$ 0.49	$ 0.48	$ 2.29	$ 1.62	$ 1.16
Basic weighted average common shares outstanding	58,603,537	58,741,973	58,760,753	58,855,156	58,825,696	58,808,098	58,778,916	58,726,420	58,739,670	58,785,118	58,789,118
Diluted net income per share	$ 0.43	$ 0.50	$ 0.73	$ 0.63	$ 0.31	$ 0.34	$ 0.49	$ 0.48	$ 2.28	$ 1.61	$ 1.15
Diluted weighted average common shares outstanding	58,936,795	59,084,117	59,051,413	59,199,622	59,222,258	59,156,432	59,100,836	59,122,812	59,067,302	59,150,920	59,225,338

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Interim Financial Data (Unaudited) - Additional Information (Detail) $ in Millions		12 Months Ended
	May 02, 2018	Dec. 31, 2018	Dec. 31, 2017 USD ($)
Quarterly Financial Data [Abstract]
Federal statutory tax rate, percentage		21.00%
Tax benefit due to change in tax rate on the deferred tax assets and deferred tax liabilities			$ 1.9
Stock split	2

Schedule II - Valuation and Qualifying Accounts and Reserves (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Warranty Reserve [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 34,999	$ 37,692	$ 33,522
Additions (Reductions) Charged to Cost and Expenses	1,104	4,268	10,852
Deductions	(5,349)	(6,961)	(6,682)
Balance at End of Period	30,754	34,999	37,692
Valuation Allowance of Deferred Tax Assets [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	3,096	4,061	4,582
Deductions	(81)	(965)	(521)
Balance at End of Period	$ 3,015	$ 3,096	$ 4,061

Revenue From Contracts With Customers - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Revenue from Contract with Customer [Abstract]
Revenue remaining performance obligation	$ 49.1
Revenue remaining performance obligation description	The Company discloses only the transaction price allocated to its remaining performance obligations on contracts with an original duration greater than one year

Inventories - Additional Information (Detail) - USD ($)	12 Months Ended
Inventories - Additional Information (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
LIFO inventory liquidations	$ 0	$ 0
Raw materials	$ 2,300,000	$ 2,200,000