Document and Entity Information - USD ($) $ in Billions	12 Months Ended
Document and Entity Information - USD ($) $ in Billions	Dec. 31, 2017	Feb. 06, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
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 Common Stock, Shares Outstanding		29,428,555
Entity Public Float			$ 2.0

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 565,153	$ 479,616	$ 440,804
Cost of sales	321,780	292,521	285,935
Gross profit	243,373	187,095	154,869
Selling, general and administrative expenses	100,993	83,140	77,463
Income from operations	142,380	103,955	77,406
Interest expense, net	461	1,125	619
Income before income taxes	141,919	102,830	76,787
Provision for income taxes	46,791	34,983	28,689
Net income	$ 95,128	$ 67,847	$ 48,098
Basic earnings per common share	$ 3.24	$ 2.31	$ 1.53
Basic weighted average common shares outstanding	29,392,559	29,394,559	31,350,542
Diluted earnings per common share	$ 3.22	$ 2.29	$ 1.52
Diluted weighted average common shares outstanding	29,575,460	29,612,669	31,682,509
Comprehensive income	$ 95,128	$ 67,847	$ 48,098

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents	$ 30,514	$ 18,664
Accounts receivable, net	66,882	48,039
Inventories	34,524	28,546
Prepaid expenses and other assets	16,878	10,400
Total current assets	148,798	105,649
Property, plant and equipment, net	103,110	103,286
Goodwill and other intangibles	71,319	10,523
Other assets	3,000	1,972
Total Assets	326,227	221,430
Current Liabilities:
Accounts payable	9,953	10,767
Accrued expenses and other liabilities	46,266	34,693
Accrued warranty	6,290	5,925
Line of Credit	0	0
Total current liabilities	62,509	51,385
Deferred income taxes	1,286	894
Non-current accrued warranty	28,709	31,767
Other long-term liabilities	2,473	3,223
Total Liabilities	94,977	87,269
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, 80,000,000 shares authorized; 34,922,111 and 34,894,233 shares issued and 29,428,430 and 29,400,552 shares outstanding at December 31, 2017 and 2016, respectively	349	349
Additional paid-in capital	122,043	120,082
Retained earnings	282,370	187,242
Treasury stock, at cost, 5,493,681 shares at December 31, 2017 and 2016, respectively	(173,512)	(173,512)
Total Stockholders' Equity	231,250	134,161
Total Liabilities and Stockholders' Equity	$ 326,227	$ 221,430

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
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	80,000,000	80,000,000
Common stock, shares issued	34,922,111	34,894,233
Common stock, shares outstanding	29,428,430	29,400,552
Treasury stock, shares	5,493,681	5,493,681

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, 2014	$ 113,385	$ 348	$ 116,740	$ 71,297	$ (75,000)
Beginning Balance, Shares at Dec. 31, 2014		32,020,123			2,780,429
Net income	48,098			48,098
Employee stock purchase and option plans	315	$ 1	314
Employee stock purchase and option plans, Shares		113,996
Shares withheld for taxes on share-based payment awards	(8,086)	$ (1)	(8,085)
Shares withheld for taxes on share-based payment awards, Shares		(115,453)
Stock-based compensation	4,861		4,861
Stock-based compensation, Shares		20,164
Excess tax benefits from stock compensation	3,117		3,117
Shares repurchased under our publicly announced share repurchase programs	(45,227)				$ (45,227)
Shares repurchased under our publicly announced share repurchase programs, Shares					1,134,300
Shares repurchased under our publicly announced share repurchase programs, Shares		(1,134,300)
Ending Balance at Dec. 31, 2015	116,463	$ 348	116,947	119,395	$ (120,227)
Ending Balance, Shares at Dec. 31, 2015		30,904,530			3,914,729
Net income	67,847			67,847
Employee stock purchase and option plans	280	$ 1	279
Employee stock purchase and option plans, Shares		79,175
Shares withheld for taxes on share-based payment awards	(1,933)	$ (1)	(1,932)
Shares withheld for taxes on share-based payment awards, Shares		(13,193)
Stock-based compensation	4,789	$ 1	4,788
Stock-based compensation, Shares		8,992
Shares repurchased under our publicly announced share repurchase programs	(53,285)				$ (53,285)
Shares repurchased under our publicly announced share repurchase programs, Shares					1,578,952
Shares repurchased under our publicly announced share repurchase programs, Shares		(1,578,952)
Ending Balance at Dec. 31, 2016	134,161	$ 349	120,082	187,242	$ (173,512)
Ending Balance, Shares at Dec. 31, 2016		29,400,552			5,493,681
Net income	95,128			95,128
Employee stock purchase and option plans	392	$ 1	391
Employee stock purchase and option plans, Shares		16,614
Shares withheld for taxes on share-based payment awards	(3,618)	$ (1)	(3,617)
Shares withheld for taxes on share-based payment awards, Shares		(29,235)
Stock-based compensation	5,187		5,187
Stock-based compensation, Shares		40,499
Ending Balance at Dec. 31, 2017	$ 231,250	$ 349	$ 122,043	$ 282,370	$ (173,512)
Ending Balance, Shares at Dec. 31, 2017		29,428,430			5,493,681

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net income	$ 95,128	$ 67,847	$ 48,098
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	16,860	14,498	14,384
Deferred income taxes	194	5,433	1,024
Stock-based compensation	5,187	4,788	4,861
Loss (Gain) on disposal of property, plant and equipment	1,738	(185)	649
Excess tax benefits from stock compensation			(3,147)
Other non-cash adjustments	(406)	(284)	(271)
Changes in operating assets and liabilities:
Accounts receivable	(10,486)	(653)	(10,995)
Inventories	(3,635)	(5,442)	643
Prepaid expenses and other assets	(2,194)	(4,256)	905
Accounts payable	(4,804)	(6,966)	(2,317)
Accrued expenses and other liabilities	2,488	9,403	7,554
Income taxes receivable/payable	1,795	1,110	1,246
Net cash provided by operating activities	101,865	85,293	62,634
Investing Activities
Expenditures for property, plant and equipment	(15,040)	(14,551)	(23,333)
Proceeds from sales of property, plant and equipment	55	4,349	35
Acquisition of business, net of cash acquired	(71,804)		(31)
Net cash used in investing activities	(86,789)	(10,202)	(23,329)
Financing Activities
Financing costs		(485)	(3)
Borrowings under line of credit	201,000	242,700	225,500
Principal payments under line of credit	(201,000)	(249,700)	(218,500)
Repurchases of common stock	(3,617)	(55,216)	(53,313)
Proceeds from employee stock purchase and option plans	391	279	315
Excess tax benefits from stock compensation			3,147
Net cash used in financing activities	(3,226)	(62,422)	(42,854)
Net increase (decrease) in cash and cash equivalents	11,850	12,669	(3,549)
Cash and cash equivalents at beginning of year	18,664	5,995	9,544
Cash and cash equivalents at end of year	30,514	18,664	5,995
Supplemental disclosures of cash flow information:
Cash paid for interest	418	852	625
Cash paid for income taxes, net	$ 44,802	$ 28,626	$ 26,327

Business and Organization

12 Months Ended

Dec. 31, 2017

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 systems and solutions for the commercial and multifamily markets, and a provider of staging, acoustical and seating systems for commercial markets, 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 and Trex Commercial Products.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

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 newly-formed, wholly-owned subsidiary, Trex Commercial Products, Inc. (Trex Commercial Products), from July 31, 2017 through December 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, 2017.

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, 2017, 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 carried at the original invoice amount less an estimate made for payment discounts and doubtful accounts. 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, 2017 and 2016.

In the years ended December 31, 2017, 2016 and 2015, sales to certain customers accounted for 10% or more of the Company’s total 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. For the year ended December 31, 2015, one customer of the Company represented approximately 27% of the Company’s net sales. At December 31, 2017, three customers represented 29%, 14%, and 11%, respectively, of the Company’s accounts receivable balance.

Approximately 33%, 33%, and 35% of the Company’s materials purchases for the years ended December 31, 2017, 2016 and 2015, respectively, 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 net realizable value. 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, 2017, the excess of the replacement cost of inventory over the LIFO value of inventory was approximately $20.1 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 staging and railing products for the commercial and multi-family markets 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 a separate operation manager at a level below the Company’s chief operating decision maker. 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, 2017, 2016 and 2015, 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, 2017, the Company had goodwill of $68.5 million that is reviewed annually for impairment.

Product Warranty

The Company warrants that its 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 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, on a quarterly basis 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

For Trex Residential Products, the Company recognizes revenue when title is transferred to customers, which is generally upon shipment of the product to the customer. The Company does not grant contractual product return rights to customers other than pursuant to its residential product warranty. The Company does not expect future product returns to be material and, consequently, does not maintain an allowance for product returns.

The Company records all shipping and handling fees in sales and records all of the related costs in cost of sales. The Company offers sales incentive programs to dealers and distributors, including rebates, pricing discounts, favorable payment terms and cooperative advertising, many of which result in cash consideration made to dealers and distributors. The Company accounts for consideration made pursuant to these programs in accordance with accounting guidance that governs consideration given by a vendor to a customer. With the exception of cooperative advertising, the Company classifies sales incentives as a reduction in revenue in “Net sales.” Sales incentives are recorded in the period in which they are earned by customers. The Company’s cooperative advertising program meets the requirements for exclusion from net sales and the costs are recorded as expenses in “Selling, general and administrative expenses” in the accompanying Consolidated Statements of Comprehensive Income. Cooperative advertising costs are expensed as incurred.

For Trex Commercial Products, the Company recognizes revenue using the percentage of completion method measured under the cost-to-cost method of accounting, whereby the Company recognizes sales and estimated profit as costs are incurred based on the proportion that the incurred costs represent of total estimated costs for each contract. Contract costs include all direct material, labor, subcontract and certain indirect costs. Administrative costs are charged to expense as incurred. Provisions for estimated losses on uncompleted contracts are recognized when such losses are determined. Changes in job performance, conditions and estimated profitability may result in revisions to costs and income and are recognized in the period they are determined. Revenues recognized in excess of amounts billed are classified under current assets and billings in excess of revenues are classified under current liabilities in the Consolidated Balance Sheets.

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, we have recognized the tax effects of the Act in our financial statements and related notes as of and for the year ended December 31, 2017. As of December 31, 2017, the Company has a valuation allowance of $3.1 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, 2017, 2016 and 2015, research and development costs were $3.8 million, $3.7 million, and $1.5 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, 2016 and 2015, $3.8 million, $2.4 million and $0.8 million, respectively, were included in prepaid expenses for production costs.

For the years ended December 31, 2017, 2016 and 2015, branding expenses, including advertising expenses as described above, were $31.0 million, $24.8 million, and $23.4 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 at December 31, 2017 and 2016.

Recently Adopted Accounting Standards

In March 2016, the FASB issued ASU No. 2016-09, “Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting.” The standard amended certain aspects of accounting for employee share-based payment transactions, including the accounting for income taxes related to those transactions and forfeitures. The standard requires recognizing excess tax benefits and deficiencies on share-based awards in the tax provision, instead of in equity. Also, the standard requires these amounts to be classified as an operating activity, and shares withheld to satisfy employee taxes to be classified as a financing activity in the statement of cash flows, rather than as financing and operating activities, respectively. The standard was effective for annual reporting periods beginning after December 15, 2016 and interim periods within that reporting period, with early adoption permitted. The Company elected to early adopt the standard in fiscal year 2016. The impact of the early adoption resulted in the following:

•

The Company recorded a tax benefit of $1.7 million within income tax expense related to the excess tax benefits of the settlement or vesting of time-based restricted stock or time-based restricted stock units and performance-based restricted stock or performance-based restricted stock units. The Company applied this guidance prospectively as of January 1, 2016 and, accordingly, data for the year ended December 31, 2015 was not adjusted. Prior to adoption this amount would have been recorded as an increase in additional paid-in capital. Going forward, this change could create volatility in the Company’s effective tax rate.

•

The Company elected to change its policy on accounting for forfeitures and recognize forfeitures as they occur. The Company applied this guidance on a modified retrospective transition method. The Company determined that the cumulative effect of applying the guidance under the modified retrospective transition method was not material to its Consolidated Financial Statements

•

Excess tax benefits are now reported as an operating activity in the Company’s Consolidated Statements of Cash Flows, rather than as a financing activity as was previously reported. As the Company applied this guidance prospectively as of January 1, 2016, excess tax benefits for the year ended December 31, 2015 were not adjusted and continue to be reported in financing activities in the Consolidated Statements of Cash Flows.

•

The standard requires the presentation of employee taxes as a financing activity in the Consolidated Statements of Cash Flows. This provision did not impact the Company’s Consolidated Financial Statements as the Company currently presents employee taxes as a financing activity in its Consolidated Statements of Cash Flows.

The Company excluded the excess tax benefits from the assumed proceeds available to repurchase shares in the computation of diluted earnings per share for 2016, which did not materially increase the diluted weighted average common shares outstanding.

New Accounting Standards Not Yet Adopted

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, the new standard). The new standard provides a single, comprehensive model for revenue arising from contracts with customers and supersedes most current revenue recognition guidance. The new standard requires an entity to recognize revenue when it satisfies a performance obligation at an amount that reflects the consideration to which the entity expects to be entitled in exchange for transferring control of goods or services to a customer. The Company will to adopt the new standard in the first quarter of fiscal 2018. The Company intends to use the retrospective application to each reporting period presented, with the option to elect certain practical expedients as defined in the new standard. The Company has completed its evaluation of its Trex Residential segment and determined that adoption of the new standard will not have a significant impact on that segment. The Company continues to evaluate the impacts of adoption on its Trex Commercial segment, which was acquired on July 31, 2017. The Company expects expanded financial statement note disclosure. The Company expects expanded financial statement note disclosure.

In February 2016, the FASB issued ASU No. 2016-02, “Leases (Topic 842).” 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 standards, 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 must be adopted using the modified retrospective transition method and provides for the option to elect a package of practical expedients upon adoption. The Company intends to adopt the standard in the first quarter of fiscal 2019 and is assessing the impact of adoption of the standard on its consolidated financial statements and related note disclosures. The Company has not made any decision on the option to elect adoption of the practical expedients.

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 is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. The guidance requires application using a retrospective transition method. The Company intends to adopt the guidance on the effective date and does not believe adoption will have a material impact on its consolidated financial statements.

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 is to 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 the effective date and does not believe adoption will have a material impact on its financial condition or results of operations.

In May 2017, the FASB issued 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 is effective prospectively for annual periods beginning on or after December 15, 2017. Early adoption is permitted. The Company intends to adopt the guidance on the effective date and does not believe adoption will have a material impact on its financial condition or results of operations.

Acquisition

12 Months Ended

Dec. 31, 2017

Business Combinations [Abstract]

Acquisition

3.	ACQUISITION

On July 31, 2017, through its newly-formed, wholly-owned subsidiary, Trex Commercial Products, 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 systems and solutions for the commercial and multifamily markets, and provides staging, acoustical and seating systems for commercial markets, 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 for the year ended December 31, 2017 include the operating results of the acquired business from the date of acquisition through year end. The Company’s consolidated balance sheet at December 31, 2017 includes the acquired assets and any liabilities assumed.

Based on the Company’s preliminary valuation, a total estimated consideration of $71.8 million has been allocated on to the assets acquired and liabilities assumed, as follows (in thousands). During the fourth quarter, a final determination of the purchase price and the final valuation report were completed upon the final determination of working capital at closing. No adjustments were made to the fair values of assets acquired and liabilities assumed as a result:


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 2017 was $1.6 million. All of the goodwill was recorded to the Trex Commercial Products reportable segment. 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.

From July 31, 2017, through December 31, 2017, Trex Commercial Products 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 during the year ended December 31, 2017, which are included in selling, general and administrative expense.

The following pro forma results are prepared for comparative purposes only and do not necessarily reflect the results that would have occurred had the acquisition occurred at the beginning of the years presented or the results which may occur in the future. The following unaudited pro forma results of operations assume the acquisition occurred on January 1, 2016 (in thousands, except per share amounts):


	Year Ended December 31
	2017		2016		2017		2016
	Actual				Pro Forma
Net sales	$	565,153	$	479,616	$	597,288	$	534,618
Net income	$	95,128	$	67,847	$	96,608	$	68,344
Basic earnings per common share	$	3.24	$	2.31	$	3.29	$	2.33
Diluted earnings per common share	$	3.22	$	2.29	$	3.27	$	2.31

Significant pro forma adjustments included in the above pro forma information include an adjustment to amortization expense for the intangible assets acquired, elimination of transaction costs related to the acquisition as such costs are considered to be non-recurring in nature, an adjustment to compensation expense related to restricted stock units granted in connection with the acquisition, the income tax effects of the adjustments based on a blended statutory rate of 38.0%.

Inventories

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Inventories

4.	INVENTORIES

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


	2017			2016
Finished goods	$	32,986		$	29,686
Raw materials		19,432			20,231

Total FIFO (first-in, first out) inventories		52,418			49,917
Reserve to adjust inventories to LIFO value		(20,070	)		(21,371	)

Total LIFO inventories	$	32,348		$	28,546

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

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 2017 and 2016.

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

Prepaid Expenses and Other Assets

12 Months Ended

Dec. 31, 2017

Text Block [Abstract]

Prepaid Expenses and Other Assets

5.	PREPAID EXPENSES AND OTHER ASSETS

Prepaid expenses and other assets consist of the following as of December 31 (in thousands):


	2017		2016
Prepaid expenses	$	7,494	$	6,209
Contract retainage		1,449		—
Revenues in excess of billings		4,841		—
Income tax receivable		2,230		4,024
Other		864		167

Total prepaid expenses and other assets	$	16,878	$	10,400

Goodwill and Other Intangible Assets

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Other Intangible Assets

6.	GOODWILL AND OTHER INTANGIBLE ASSETS

The following table summarizes the activity related to the carrying amount of goodwill during the year ended December 31, 2017 (in thousands):


	2017
Beginning balance, January 1	$	10,523
Goodwill recognized from acquisition of SC Company		57,938

Ending balance, December 31	$	68,461

The following table reports the carrying amount of goodwill by reportable segment as of December 31, 2017 (in thousands):


	2017
Trex Residential Products	$	14,216
Trex Commercial Products		54,245

Ending Balance, December 31	$	68,461

Intangible assets acquired from SC Company on July 31, 2017 consist of the following at December 31, 2017:


	Net Carrying Amount			Amortization Period
	(in thousands)			(in months)
Intangible assets:
Customer backlog	$	4,000			12
Trade names and trademarks		900			12

Total intangible assets		4,900

Accumulated amortization:
Customer backlog		(1,666	)
Trade name		(376	)

Total accumulated amortization		(2,042	)

Intantible assets, net	$	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 bases, which approximates the pattern in which the economic benefits are expected to be received. Amortization expense for the year ended December 31, 2017 was $2.0 million.

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Property, Plant and Equipment

12 Months Ended

Dec. 31, 2017

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):


	2017			2016
Building and improvements	$	49,403		$	47,859
Machinery and equipment		228,107			223,450
Furniture and fixtures		1,620			2,710
Forklifts and tractors		9,799			10,167
Computer equipment		9,680			10,481
Construction in process		5,954			4,172
Land		11,417			11,417

Total property, plant and equipment		315,980			310,256
Accumulated depreciation		(212,870	)		(206,970	)

Total property, plant and equipment, net	$	103,110		$	103,286

The Company had construction in process as of December 31, 2017 of approximately $5.9 million. The Company expects that the construction in process will be completed and put into service in the year ending December 31, 2018.

Depreciation expense for the years ended December 31, 2017, 2016, and 2015 totaled $14.7 million, $14.2 million, and $14.3 million, respectively.

In January 2016, the Company sold a portion of the Olive Branch facility that contained the buildings for $4.2 million and recognized a $0.1 million gain on sale, which is reported in “Selling, general and administrative expenses” in the Consolidated Statements of Comprehensive Income. As of December 31, 2017, the Company continues to own approximately 62 acres of undeveloped land that is reported in “Property, plant and equipment, net” in the Consolidated Balance Sheet.

Accrued Expenses and Other Liabilities

12 Months Ended

Dec. 31, 2017

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):


	2017		2016
Sales and marketing costs	$	21,964	$	16,707
Compensation and benefits		14,818		13,298
Manufacturing costs		1,979		1,799
Billings in excess of revenues		1,842		—
Customer deposits		1,230		—
Rent obligations		779		632
Other		3,654		2,257

Total accrued expenses	$	46,266	$	34,693

Debt

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Debt

DEBT

The Company’s debt consists of a revolving credit facility. At December 31, 2017 and 2016, the Company had no outstanding indebtedness. Available borrowing capacity at December 31, 2017, 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, 2017. 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, 2017

Equity [Abstract]

Stockholders' Equity

11.

STOCKHOLDERS’ EQUITY

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,
	2017		2016		2015
Numerator:
Net income	$	95,128	$	67,847	$	48,098

Denominator:
Basic weighted average shares outstanding		29,392,559		29,394,559		31,350,542
Effect of dilutive securities:
SARS		99,321		125,119		197,299
Restricted stock		83,580		92,991		134,668

Diluted weighted average shares outstanding		29,575,460		29,612,669		31,682,509

Basic earnings per share	$	3.24	$	2.31	$	1.53

Diluted earnings per share	$	3.22	$	2.29	$	1.52

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,
	2017		2016		2015
Restricted stock		83		12		501
Stock appreciation rights		10,617		4,631		5,828

Stock Repurchase Programs

On October 23, 2014, the Board of Directors authorized a common stock repurchase program of up to 2.0 million shares of the Company’s outstanding common stock (October 2014 Stock Repurchase Program). This authorization had no expiration date. During 2015, the Company repurchased 1,134,300 shares for $45.2 million under the October 2014 Stock Repurchase Program. On October 22, 2015, the Board of Directors terminated the October 2014 Stock Repurchase Program and adopted a new 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 2.9 million shares of the Company’s outstanding common stock (February 2018 Stock Repurchase Program). As of the date of this report, the Company has made no repurchases under the February 2018 Stock Repurchase Program.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

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

Stock-Based Compensation

12.

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 6,420,000.

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,
	2017		2016		2015
Time-based restricted stock and time-based restricted stock units	$	1,992	$	2,281	$	2,704
Performance-based restricted stock and performance-based restricted stock units		2,805		2,210		1,562
Stock appreciation rights		251		184		525
Employee stock purchase plan		139		113		70

Total stock-based compensation	$	5,187	$	4,788	$	4,861

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, 2017, 2016 and 2015 was $5.5 million, $1.7 million, and $9.8 million, respectively. At December 31, 2017, there was $2.1 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 1.8 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, 2014		329,562		$	18.89
Granted		57,598		$	43.81
Vested		(230,704	)	$	42.37
Forfeited		(48,549	)	$	20.20

Nonvested at December 31, 2015		107,907		$	29.43
Granted		57,874		$	37.64
Vested		(43,848	)	$	42.34
Forfeited		(133	)	$	43.89

Nonvested at December 31, 2016		121,800		$	31.59
Granted		36,201		$	72.54
Vested		(81,186	)	$	28.90
Forfeited		(256	)	$	37.36

Nonvested at December 31, 2017		76,559		$	53.79

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, 2017, 2016, and 2015 there was $1.8 million, $1.2 million, and $0.6 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 1.9 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, 2014		42,676		$	33.72
Granted		34,638		$	43.89
Vested		(35,679	)	$	41.91
Forfeited		(12,538	)	$	38.12

Nonvested at December 31, 2015		29,097		$	39.38
Granted		44,925		$	35.83
Vested		(14,949	)	$	35.71
Forfeited		(657	)	$	33.72

Nonvested at December 31, 2016		58,416		$	36.63
Granted		43,307		$	57.54
Vested		(43,394	)	$	37.27
Forfeited		—		$	—

Nonvested at December 31, 2017		58,329		$	51.69

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, 2017, there was $0.3 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, 2017 and 2015, respectively, the assumptions shown in the following table were used:


	December 31,
	2017			2015
Dividend yield		0	%		0	%
Average risk-free interest rate		2.0	%		1.6	%
Expected term (years)		5			5
Expected volatility		42.3	%		42.9	%

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, 2017 and 2015 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, 2017 and 2015 was $27.97 and $16.26, 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, 2017
Outstanding at December 31, 2014		515,830		$	13.98
Granted		15,585		$	41.19
Exercised		(263,626	)	$	13.86
Canceled		(5,712	)	$	21.94

Outstanding at December 31, 2015		262,077		$	13.13
Granted		—		$	—
Exercised		(124,352	)	$	11.09
Canceled		—		$	—

Outstanding at December 31, 2016		137,725		$	19.57
Granted		18,739		$	70.75
Exercised		(17,406	)	$	16.13
Canceled		—		$	—

Outstanding at December 31, 2017		139,058		$	26.89		5.3	$	11,333,033
Vested at December 31, 2017		139,058		$	26.89		5.3	$	11,333,033
Exercisable at December 31, 2017		115,191		$	19.12		4.6	$	10,282,908

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 600,000. Through December 31, 2017, employees had purchased approximately 429,073 shares under the plan.

Stock Options

Stock options are granted with an exercise 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 options are generally forfeitable upon termination of a holder’s service as an employee or director, unless the individual’s service is terminated due to retirement, death or permanent disability. The fair value of each stock option award is estimated on the date of grant using a Black-Scholes option-pricing model. The Company recognizes compensation cost on a straight-line basis over the vesting period for the award. All outstanding options were exercised during fiscal 2015 and there were no stock options outstanding at December 31, 2017 and 2016.

Leases

12 Months Ended

Dec. 31, 2017

Leases [Abstract]

Leases

13.

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, 2017 were as follows (in thousands):


Year Ending December 31,
2018	$	10,626
2019		9,344
2020		7,223
2021		6,716
2022		4,843
Thereafter		14,046

Total minimum lease payments	$	52,798

For the years ended December 31, 2017, 2016 and 2015, the Company recognized rental expenses of approximately $9.1 million, $9.9 million, and $7.7 million, respectively.

Employee Benefit Plans

12 Months Ended

Dec. 31, 2017

Postemployment Benefits [Abstract]

Employee Benefit Plans

14.

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 for every $1.00 contributed by an employee to the plan up to 6% of compensation.

The Company’s contributions to the plans totaled $3.0 million, $2.5 million, and $2.2 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

15.

INCOME TAXES

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


	Year Ended December 31,
	2017			2016		2015
Current income tax provision:
Federal	$	41,177		$	26,752	$	25,105
State		5,420			2,798		2,560

		46,597			29,550		27,665

Deferred income tax provision:
Federal		1,177			5,217		987
State		(983	)		216		37

		194			5,433		1,024

Total income tax provision	$	46,791		$	34,983	$	28,689

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,
	2017			2016			2015
U.S. Federal statutory taxes	$	49,671		$	35,990		$	26,876
State and local taxes, net of U.S. Federal benefit		5,110			3,747			2,806
Permanent items		576			396			1,308
Excess tax benefits from vesting or settlement of stock compensation awards		(1,454	)		(1,749	)		—
Domestic production activities deduction		(4,376	)		(2,740	)		(2,262	)
Federal credits		(534	)		(488	)		(328	)
Other		(2,202	)		(173	)		289

Total income tax provision	$	46,791		$	34,983		$	28,689

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


	As of December 31,
	2017			2016
Deferred tax assets:
Net operating losses	$	123		$	93
Residential product warranty reserve		8,876			14,510
Stock-based compensation		1,823			2,186
Accruals not currently deductible and other		1,838			2,261
Inventories		3,783			5,785
State tax credit carryforwards		3,619			4,020

Gross deferred tax assets, before valuation allowance		20,062			28,855
Valuation allowance		(3,096	)		(4,061	)

Gross deferred tax assets, after valuation allowance		16,966			24,794

Deferred tax liabilities:
Depreciation and other		(18,055	)		(25,688	)

Gross deferred tax liabilities		(18,055	)		(25,688	)

Net deferred tax (liability) asset	$	(1,089	)	$	(894	)

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 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, which is included in “Other” in the above tax rate reconciliation. We continue to analyze certain aspects of the Act and refine our calculation, which could potentially affect the measurement of these balances or give rise to new deferred tax amounts. As of December 31, 2017, the Company had a valuation allowance of $3.1 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.

In 2016, the Company adopted ASU No. 2016-09, “Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting,” and, accordingly, recognizes excess tax benefits for stock-based awards within income tax expense when realized. The Company applied the guidance in the new standard prospectively as of January 1, 2016. Excess tax benefits for the year ended December 31, 2015 are recorded in additional paid-in-capital. The Company realized $1.5 million and $1.7 million of excess tax benefits during 2017 and 2016, respectively.

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, 2017, 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, 2017, Federal tax years 2013 through 2016 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, 2017

Segment Reporting [Abstract]

Segment Information

16.

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 Products 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 Products net sales were $543.3 million, $479.6 million, and $440.8 million, in the years ended December 31, 2017, 2016, and 2015, respectively.

•

Trex Commercial Products designs, engineers, and markets modular and architectural railing systems and solutions for the commercial and multifamily markets, and staging, acoustical and seating systems for commercial markets, 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 Products net sales were $21.8 million from the date of acquisition through December 31, 2017.

The Company’s operating 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 for the year ended December 31, 2017, includes data for Trex Residential Products for the year ended December 31, 2017, and data for Trex Commercial Products from the date of the acquisition of SC Company through December 31, 2017 (in thousands):


	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

Reconciliation of net income to EBITDA:


	Year Ended December 31, 2017
	Residential		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, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

18.

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, 2017, 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, 2017, the Company has purchase commitments under material supply contracts of $47.2 million, $9.5 million, and $5.9 million for the years ending December 31, 2018, 2019, and 2020, respectively.

Product Warranty

The Company warrants that its 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 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 claims received in the year ended December 31, 2017 was lower than claims received in the year ended December 31, 2016, and consistent with the Company’s expectations for 2017. Also, the average settlement cost per claim experienced in the year ended December 31, 2017 was lower than the average settlement cost per claim experienced during the year ended December 31, 2016 and consistent with the Company’s expectation for 2017. Based on the facts and circumstances at December 31, 2017, the Company believes its reserve is sufficient to cover future surface flaking obligations. 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 $2.8 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, 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


	Year Ended December 31, 2016
	Surface Flaking			Other Residential			Total
Beginning balance, January 1	$	29,673		$	3,849		$	33,522
Provisions and changes in estimates		9,835			1,017			10,852
Settlements made during the period		(5,661	)		(1,021	)		(6,682	)

Ending balance, December 31	$	33,847		$	3,845		$	37,692

Interim Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Interim Financial Data (Unaudited)

19.

INTERIM FINANCIAL DATA (Unaudited)


	Three Months Ended
	December 31, 2017		September 30, 2017		June 30, 2017		March 31, 2017		December 31, 2016		September 30, 2016		June 30, 2016		March 31, 2016
	(In thousands, except share and per share data)
Net sales	$	122,212	$	140,194	$	157,941	$	144,806	$	95,322	$	106,168	$	146,450	$	131,676
Gross profit	$	50,906	$	55,284	$	72,014	$	65,169	$	38,113	$	29,945	$	61,410	$	57,627
Net income	$	18,299	$	20,098	$	28,782	$	27,949	$	12,629	$	7,787	$	23,725	$	23,706
Basic net income per share	$	0.62	$	0.68	$	0.98	$	0.95	$	0.43	$	0.27	$	0.81	$	0.80
Basic weighted average common shares outstanding		29,412,848		29,404,049		29,389,458		29,363,210		29,318,915		29,295,284		29,264,362		29,697,722
Diluted net income per share	$	0.62	$	0.68	$	0.97	$	0.95	$	0.43	$	0.26	$	0.80	$	0.79
Diluted weighted average common shares outstanding		29,611,129		29,578,216		29,550,418		29,561,406		29,543,842		29,516,718		29,477,870		29,910,292

The Company’s operating results 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 Trex products to a later 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.

Schedule II - Valuation and Qualifying Accounts and Reserves

12 Months Ended

Dec. 31, 2017

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, 2017:
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:
Residential product warranty reserve	$	33,522	$	10,852	$	(6,682	)	$	37,692

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

Year ended December 31, 2015:
Residential product warranty reserve	$	33,841	$	8,515	$	(8,834	)	$	33,522

Income tax valuation allowance	$	4,465	$	117	$	—		$	4,582

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

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

Approximately 33%, 33%, and 35% of the Company’s materials purchases for the years ended December 31, 2017, 2016 and 2015, respectively, 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

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, 2017, 2016 and 2015, branding expenses, including advertising expenses as described above, were $31.0 million, $24.8 million, and $23.4 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, 2017

Business Combinations [Abstract]

Summary of Estimated Consideration Allocated on a Preliminary Basis to Assets Acquired and Liabilities Assumed


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

Summary of Unaudited Pro Forma Results of Operations


	Year Ended December 31
	2017		2016		2017		2016
	Actual				Pro Forma
Net sales	$	565,153	$	479,616	$	597,288	$	534,618
Net income	$	95,128	$	67,847	$	96,608	$	68,344
Basic earnings per common share	$	3.24	$	2.31	$	3.29	$	2.33
Diluted earnings per common share	$	3.22	$	2.29	$	3.27	$	2.31

Inventories (Tables)

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Summary of Inventories

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


	2017			2016
Finished goods	$	32,986		$	29,686
Raw materials		19,432			20,231

Total FIFO (first-in, first out) inventories		52,418			49,917
Reserve to adjust inventories to LIFO value		(20,070	)		(21,371	)

Total LIFO inventories	$	32,348		$	28,546

Prepaid Expenses and Other Assets (Tables)

12 Months Ended

Dec. 31, 2017

Text Block [Abstract]

Summary of Prepaid Expenses and Other Assets

Prepaid expenses and other assets consist of the following as of December 31 (in thousands):


	2017		2016
Prepaid expenses	$	7,494	$	6,209
Contract retainage		1,449		—
Revenues in excess of billings		4,841		—
Income tax receivable		2,230		4,024
Other		864		167

Total prepaid expenses and other assets	$	16,878	$	10,400

Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Activity Related to Carrying Amount of Goodwill

The following table summarizes the activity related to the carrying amount of goodwill during the year ended December 31, 2017 (in thousands):


	2017
Beginning balance, January 1	$	10,523
Goodwill recognized from acquisition of SC Company		57,938

Ending balance, December 31	$	68,461

Summary of Carrying Amount of Goodwill by Reportable Segment

The following table reports the carrying amount of goodwill by reportable segment as of December 31, 2017 (in thousands):


	2017
Trex Residential Products	$	14,216
Trex Commercial Products		54,245

Ending Balance, December 31	$	68,461

Details of Intangible Assets Acquired

Intangible assets acquired from SC Company on July 31, 2017 consist of the following at December 31, 2017:


	Net Carrying Amount			Amortization Period
	(in thousands)			(in months)
Intangible assets:
Customer backlog	$	4,000			12
Trade names and trademarks		900			12

Total intangible assets		4,900

Accumulated amortization:
Customer backlog		(1,666	)
Trade name		(376	)

Total accumulated amortization		(2,042	)

Intantible assets, net	$	2,858

Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

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):


	2017			2016
Building and improvements	$	49,403		$	47,859
Machinery and equipment		228,107			223,450
Furniture and fixtures		1,620			2,710
Forklifts and tractors		9,799			10,167
Computer equipment		9,680			10,481
Construction in process		5,954			4,172
Land		11,417			11,417

Total property, plant and equipment		315,980			310,256
Accumulated depreciation		(212,870	)		(206,970	)

Total property, plant and equipment, net	$	103,110		$	103,286

Accrued Expenses and Other Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Summary of Accrued Expenses and Other Liabilities

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


	2017		2016
Sales and marketing costs	$	21,964	$	16,707
Compensation and benefits		14,818		13,298
Manufacturing costs		1,979		1,799
Billings in excess of revenues		1,842		—
Customer deposits		1,230		—
Rent obligations		779		632
Other		3,654		2,257

Total accrued expenses	$	46,266	$	34,693

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

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,
	2017		2016		2015
Numerator:
Net income	$	95,128	$	67,847	$	48,098

Denominator:
Basic weighted average shares outstanding		29,392,559		29,394,559		31,350,542
Effect of dilutive securities:
SARS		99,321		125,119		197,299
Restricted stock		83,580		92,991		134,668

Diluted weighted average shares outstanding		29,575,460		29,612,669		31,682,509

Basic earnings per share	$	3.24	$	2.31	$	1.53

Diluted earnings per share	$	3.22	$	2.29	$	1.52

Antidilutive Securities Excluded from Computation of Earnings Per Share

The computation of diluted earnings per share excludes the following potentially dilutive securities because the effect would be anti-dilutive:


	Year Ended December 31,
	2017		2016		2015
Restricted stock		83		12		501
Stock appreciation rights		10,617		4,631		5,828

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Stock-Based Compensation Expense

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


	Year Ended December 31,
	2017		2016		2015
Time-based restricted stock and time-based restricted stock units	$	1,992	$	2,281	$	2,704
Performance-based restricted stock and performance-based restricted stock units		2,805		2,210		1,562
Stock appreciation rights		251		184		525
Employee stock purchase plan		139		113		70

Total stock-based compensation	$	5,187	$	4,788	$	4,861

Summary of Assumptions Used to Estimate Fair Value of Each SAR

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, 2017 and 2015, respectively, the assumptions shown in the following table were used:


	December 31,
	2017			2015
Dividend yield		0	%		0	%
Average risk-free interest rate		2.0	%		1.6	%
Expected term (years)		5			5
Expected volatility		42.3	%		42.9	%

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, 2017
Outstanding at December 31, 2014		515,830		$	13.98
Granted		15,585		$	41.19
Exercised		(263,626	)	$	13.86
Canceled		(5,712	)	$	21.94

Outstanding at December 31, 2015		262,077		$	13.13
Granted		—		$	—
Exercised		(124,352	)	$	11.09
Canceled		—		$	—

Outstanding at December 31, 2016		137,725		$	19.57
Granted		18,739		$	70.75
Exercised		(17,406	)	$	16.13
Canceled		—		$	—

Outstanding at December 31, 2017		139,058		$	26.89		5.3	$	11,333,033
Vested at December 31, 2017		139,058		$	26.89		5.3	$	11,333,033
Exercisable at December 31, 2017		115,191		$	19.12		4.6	$	10,282,908

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, 2014		329,562		$	18.89
Granted		57,598		$	43.81
Vested		(230,704	)	$	42.37
Forfeited		(48,549	)	$	20.20

Nonvested at December 31, 2015		107,907		$	29.43
Granted		57,874		$	37.64
Vested		(43,848	)	$	42.34
Forfeited		(133	)	$	43.89

Nonvested at December 31, 2016		121,800		$	31.59
Granted		36,201		$	72.54
Vested		(81,186	)	$	28.90
Forfeited		(256	)	$	37.36

Nonvested at December 31, 2017		76,559		$	53.79

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, 2014		42,676		$	33.72
Granted		34,638		$	43.89
Vested		(35,679	)	$	41.91
Forfeited		(12,538	)	$	38.12

Nonvested at December 31, 2015		29,097		$	39.38
Granted		44,925		$	35.83
Vested		(14,949	)	$	35.71
Forfeited		(657	)	$	33.72

Nonvested at December 31, 2016		58,416		$	36.63
Granted		43,307		$	57.54
Vested		(43,394	)	$	37.27
Forfeited		—		$	—

Nonvested at December 31, 2017		58,329		$	51.69

Leases (Tables)

12 Months Ended

Dec. 31, 2017

Leases [Abstract]

Minimum Annual Payments Under Non-Cancelable Leases

Minimum annual payments under these non-cancelable leases as of December 31, 2017 were as follows (in thousands):


Year Ending December 31,
2018	$	10,626
2019		9,344
2020		7,223
2021		6,716
2022		4,843
Thereafter		14,046

Total minimum lease payments	$	52,798

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Tax Provision (Benefit)

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


	Year Ended December 31,
	2017			2016		2015
Current income tax provision:
Federal	$	41,177		$	26,752	$	25,105
State		5,420			2,798		2,560

		46,597			29,550		27,665

Deferred income tax provision:
Federal		1,177			5,217		987
State		(983	)		216		37

		194			5,433		1,024

Total income tax provision	$	46,791		$	34,983	$	28,689

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,
	2017			2016			2015
U.S. Federal statutory taxes	$	49,671		$	35,990		$	26,876
State and local taxes, net of U.S. Federal benefit		5,110			3,747			2,806
Permanent items		576			396			1,308
Excess tax benefits from vesting or settlement of stock compensation awards		(1,454	)		(1,749	)		—
Domestic production activities deduction		(4,376	)		(2,740	)		(2,262	)
Federal credits		(534	)		(488	)		(328	)
Other		(2,202	)		(173	)		289

Total income tax provision	$	46,791		$	34,983		$	28,689

Schedule of Deferred Tax Assets and Liabilities

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


	As of December 31,
	2017			2016
Deferred tax assets:
Net operating losses	$	123		$	93
Residential product warranty reserve		8,876			14,510
Stock-based compensation		1,823			2,186
Accruals not currently deductible and other		1,838			2,261
Inventories		3,783			5,785
State tax credit carryforwards		3,619			4,020

Gross deferred tax assets, before valuation allowance		20,062			28,855
Valuation allowance		(3,096	)		(4,061	)

Gross deferred tax assets, after valuation allowance		16,966			24,794

Deferred tax liabilities:
Depreciation and other		(18,055	)		(25,688	)

Gross deferred tax liabilities		(18,055	)		(25,688	)

Net deferred tax (liability) asset	$	(1,089	)	$	(894	)

Segment Information (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Details of Segment Information

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


	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, 2017
	Residential		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, 2017

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, 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


	Year Ended December 31, 2016
	Surface Flaking			Other Residential			Total
Beginning balance, January 1	$	29,673		$	3,849		$	33,522
Provisions and changes in estimates		9,835			1,017			10,852
Settlements made during the period		(5,661	)		(1,021	)		(6,682	)

Ending balance, December 31	$	33,847		$	3,845		$	37,692

Interim Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Summary of Interim Financial Data


	Three Months Ended
	December 31, 2017		September 30, 2017		June 30, 2017		March 31, 2017		December 31, 2016		September 30, 2016		June 30, 2016		March 31, 2016
	(In thousands, except share and per share data)
Net sales	$	122,212	$	140,194	$	157,941	$	144,806	$	95,322	$	106,168	$	146,450	$	131,676
Gross profit	$	50,906	$	55,284	$	72,014	$	65,169	$	38,113	$	29,945	$	61,410	$	57,627
Net income	$	18,299	$	20,098	$	28,782	$	27,949	$	12,629	$	7,787	$	23,725	$	23,706
Basic net income per share	$	0.62	$	0.68	$	0.98	$	0.95	$	0.43	$	0.27	$	0.81	$	0.80
Basic weighted average common shares outstanding		29,412,848		29,404,049		29,389,458		29,363,210		29,318,915		29,295,284		29,264,362		29,697,722
Diluted net income per share	$	0.62	$	0.68	$	0.97	$	0.95	$	0.43	$	0.26	$	0.80	$	0.79
Diluted weighted average common shares outstanding		29,611,129		29,578,216		29,550,418		29,561,406		29,543,842		29,516,718		29,477,870		29,910,292

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) Customer Institution Supplier	Dec. 31, 2016 USD ($) Customer	Dec. 31, 2015 USD ($) Customer	Dec. 31, 2010 USD ($)
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	1
Number of customer accounted for 10% or more account receivable \| Customer	3
Number of largest raw material suppliers \| Supplier	4
Excess of the replacement cost of inventory over the LIFO value of inventory	$ 20,100,000
Annual impairment test of goodwill	0	$ 0	$ 0
Goodwill	68,461,000	10,523,000
Valuation allowance	3,096,000	4,061,000
Research and Development costs	3,800,000	3,700,000	1,500,000
Prepaid expenses for production costs of advertising	3,800,000	2,400,000	800,000
Branding Expenses	31,000,000	24,800,000	23,400,000
Income tax expense (benefit)	46,791,000	34,983,000	$ 28,689,000
Accounting Standards Update 2016-09 [Member]
Schedule Of Significant Accounting Policies [Line Items]
Income tax expense (benefit)	$ (1,500,000)	$ (1,700,000)
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
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	41.00%	39.00%	27.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer One [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	29.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Two [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	14.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Three [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	11.00%
Raw Materials [Member] \| Supplier Concentration Risk [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	33.00%	33.00%	35.00%
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, 2017
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 ($) $ in Thousands			3 Months Ended								5 Months Ended	12 Months Ended
	Aug. 17, 2017	Jul. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Fund used to acquire business from revolving credit facility			$ 0				$ 0				$ 0	$ 0	$ 0
Repayment of revolving credit facility												201,000	249,700	$ 218,500
Goodwill			68,461				10,523				68,461	68,461	10,523
Net sales			122,212	$ 140,194	$ 157,941	$ 144,806	95,322	$ 106,168	$ 146,450	$ 131,676		565,153	479,616	440,804
Net income (loss)			18,299	$ 20,098	$ 28,782	$ 27,949	$ 12,629	$ 7,787	$ 23,725	$ 23,706		95,128	$ 67,847	$ 48,098
Acquisition-related expenses												$ 500
Blended statutory rate												38.00%
Trex Commercial Products, Inc. (TCP) [Member]
Business Acquisition [Line Items]
Net sales											21,800
Net income (loss)											(2,300)
Staging Concepts Acquisition, LLC [Member]
Business Acquisition [Line Items]
Certain assets and liabilities acquired in cash		$ 71,800
Estimated consideration			71,804								71,804	$ 71,804
Goodwill			57,938								57,938	57,938
Goodwill expected to be amortized and deductible for tax purposes			$ 1,600								$ 1,600	$ 1,600
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
Repayment of revolving credit facility	$ 30,000

Acquisition - Summary of Estimated Consideration Allocated on a Preliminary Basis to Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 68,461	$ 10,523
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

Acquisition - Summary of Unaudited Pro Forma Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Combinations [Abstract]
Net sales	$ 122,212	$ 140,194	$ 157,941	$ 144,806	$ 95,322	$ 106,168	$ 146,450	$ 131,676	$ 565,153	$ 479,616	$ 440,804
Net income	$ 18,299	$ 20,098	$ 28,782	$ 27,949	$ 12,629	$ 7,787	$ 23,725	$ 23,706	$ 95,128	$ 67,847	$ 48,098
Basic earnings per common share	$ 0.62	$ 0.68	$ 0.98	$ 0.95	$ 0.43	$ 0.27	$ 0.81	$ 0.80	$ 3.24	$ 2.31	$ 1.53
Diluted earnings per common share	$ 0.62	$ 0.68	$ 0.97	$ 0.95	$ 0.43	$ 0.26	$ 0.80	$ 0.79	$ 3.22	$ 2.29	$ 1.52
Pro Forma Net sales									$ 597,288	$ 534,618
Pro Forma Net income									$ 96,608	$ 68,344
Pro Forma Basic earnings per common share									$ 3.29	$ 2.33
Pro Forma Diluted earnings per common share									$ 3.27	$ 2.31

Inventories - Summary of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Inventory [Line Items]
Raw materials	$ 2,200
Reserve to adjust inventories to LIFO value	(20,100)
Total LIFO inventories	34,524	$ 28,546
LIFO [Member]
Inventory [Line Items]
Finished goods	32,986	29,686
Raw materials	19,432	20,231
Total FIFO (first-in, first out) inventories	52,418	49,917
Reserve to adjust inventories to LIFO value	(20,070)	(21,371)
Total LIFO inventories	$ 32,348	$ 28,546

Prepaid Expenses and Other Assets - Summary of Prepaid Expenses and Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Prepaid Expense and Other Assets [Abstract]
Prepaid expenses	$ 7,494	$ 6,209
Contract retainage	1,449
Revenues in excess of billings	4,841
Income tax receivable	2,230	4,024
Other	864	167
Total prepaid expenses and other assets	$ 16,878	$ 10,400

Goodwill and Other Intangible Assets - Summary of Activity Related to Carrying Amount of Goodwill (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Beginning balance	$ 10,523
Goodwill recognized from acquisition of SC Company	57,938
Ending balance	$ 68,461

Goodwill and Other Intangible Assets - Summary of Carrying Amount of Goodwill by Reportable Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 68,461	$ 10,523
Residential [Member]
Goodwill [Line Items]
Goodwill	14,216
Commercial [Member]
Goodwill [Line Items]
Goodwill	$ 54,245

Goodwill and Other Intangible Assets - Details of Intangible Assets Acquired (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Net carrying amount,Intangible assets	$ 4,900
Net carrying amount, Accumulated amortization	(2,042)
Intantible assets, net	2,858
Customer Backlog [Member]
Indefinite-lived Intangible Assets [Line Items]
Net carrying amount,Intangible assets	4,000
Net carrying amount, Accumulated amortization	$ (1,666)
Amortization period	12 months
Trade Names and Trademarks [Member]
Indefinite-lived Intangible Assets [Line Items]
Net carrying amount,Intangible assets	$ 900
Amortization period	12 months
Trade Name [Member]
Indefinite-lived Intangible Assets [Line Items]
Net carrying amount, Accumulated amortization	$ (376)

Property, Plant and Equipment - Summary of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 315,980	$ 310,256
Accumulated depreciation	(212,870)	(206,970)
Total property, plant and equipment, net	103,110	103,286
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	49,403	47,859
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	228,107	223,450
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,620	2,710
Forklifts and Tractors [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	9,799	10,167
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	9,680	10,481
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	5,954	4,172
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 11,417	$ 11,417

Property, Plant and Equipment - Additional Information (Detail) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) a	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross		$ 315,980	$ 310,256
Depreciation expense		14,700	14,200	$ 14,300
Proceeds from sales of property, plant and equipment		55	4,349	35
Gain (loss) on disposal of property, plant and equipment		$ (1,738)	185	$ (649)
Olive Branch Assets [Member]
Property, Plant and Equipment [Line Items]
Proceeds from sales of property, plant and equipment	$ 4,200
Gain (loss) on disposal of property, plant and equipment	$ 100
Area of land owned \| a		62
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross		$ 5,954	$ 4,172

Accrued Expenses and Other Liabilities - Summary of Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Sales and marketing costs	$ 21,964	$ 16,707
Compensation and benefits	14,818	13,298
Manufacturing costs	1,979	1,799
Billings in excess of revenues	1,842
Customer deposits	1,230
Rent obligations	779	632
Other	3,654	2,257
Total accrued expenses	$ 46,266	$ 34,693

Debt - Additional Information (Detail)		3 Months Ended	12 Months Ended
Debt - Additional Information (Detail)	Jan. 12, 2016	Dec. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Remaining available borrowing capacity		$ 200,000,000	$ 200,000,000
Company indebtedness		0	$ 0
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 - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income	$ 18,299	$ 20,098	$ 28,782	$ 27,949	$ 12,629	$ 7,787	$ 23,725	$ 23,706	$ 95,128	$ 67,847	$ 48,098
Denominator:
Basic weighted average shares outstanding	29,412,848	29,404,049	29,389,458	29,363,210	29,318,915	29,295,284	29,264,362	29,697,722	29,392,559	29,394,559	31,350,542
Effect of dilutive securities:
Diluted weighted average shares outstanding	29,611,129	29,578,216	29,550,418	29,561,406	29,543,842	29,516,718	29,477,870	29,910,292	29,575,460	29,612,669	31,682,509
Basic earnings per share	$ 0.62	$ 0.68	$ 0.98	$ 0.95	$ 0.43	$ 0.27	$ 0.81	$ 0.80	$ 3.24	$ 2.31	$ 1.53
Diluted earnings per share	$ 0.62	$ 0.68	$ 0.97	$ 0.95	$ 0.43	$ 0.26	$ 0.80	$ 0.79	$ 3.22	$ 2.29	$ 1.52
Stock Appreciation Rights [Member]
Effect of dilutive securities:
Dilutive securities									99,321	125,119	197,299
Restricted Stock [Member]
Effect of dilutive securities:
Dilutive securities									83,580	92,991	134,668

Stockholders' Equity - Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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	83	12	501
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	10,617	4,631	5,828

Stockholders' Equity - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 16, 2018	Feb. 16, 2017	Oct. 22, 2015	Oct. 23, 2014
October 2014 Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase program, authorized shares							2,000,000
Number of shares repurchased by the Company			1,134,300
Value of shares repurchased by the Company			$ 45.2
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, authorized shares						3,150,000
Number of shares repurchased by the Company		1,578,952
Value of shares repurchased by the Company		$ 53.3
Common stock repurchase program, termination date	Dec. 31, 2016
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]
Number of shares repurchased by the Company	0
February 2018 Stock Repurchase Program [Member] \| Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase program, authorized shares				2,900,000

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Approximate number of shares employees purchased under the Employee Stock Purchase Plan		429,073
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	6,420,000	6,420,000
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 10 months 25 days
Unrecognized compensation cost related to unvested awards	$ 1.8	$ 1.8	$ 1.2	$ 0.6
Vesting period		3 years
Number of shares or rights issued		43,307	44,925	34,638
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			$ 0.3
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		$ 27.97		$ 16.26
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		1 year 9 months 18 days
Unrecognized compensation cost related to unvested awards	$ 2.1	$ 2.1
Total fair value of restricted shares vested		$ 5.5	$ 1.7	$ 9.8
Number of shares or rights issued		36,201	57,874	57,598
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	600,000	600,000
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, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 5,187	$ 4,788	$ 4,861
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	1,992	2,281	2,704
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	2,805	2,210	1,562
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	251	184	525
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 139	$ 113	$ 70

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, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Restricted Stock Activity [Line Items]
Nonvested, Shares, Beginning Balance	121,800	107,907	329,562
Time-based Restricted Stock, Granted	36,201	57,874	57,598
Time-based Restricted Stock, Vested	(81,186)	(43,848)	(230,704)
Time-based Restricted Stock, Forfeited	(256)	(133)	(48,549)
Nonvested, Shares, Ending Balance	76,559	121,800	107,907
Nonvested, Weighted-Average Grant Price Per Share, Beginning Balance	$ 31.59	$ 29.43	$ 18.89
Weighted-Average Grant Price Per Share, Granted	72.54	37.64	43.81
Weighted-Average Grant Price Per Share, Vested	28.90	42.34	42.37
Weighted-Average Grant Price Per Share, Forfeited	37.36	43.89	20.20
Nonvested, Weighted-Average Grant Price Per Share, Ending Balance	$ 53.79	$ 31.59	$ 29.43

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, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Restricted Stock Activity [Line Items]
Nonvested, Shares, Beginning Balance	58,416	29,097	42,676
Performance-based Restricted Stock, Granted	43,307	44,925	34,638
Performance-based Restricted Stock, Vested	(43,394)	(14,949)	(35,679)
Performance-based Restricted Stock, Forfeited		(657)	(12,538)
Nonvested, Shares, Ending Balance	58,329	58,416	29,097
Nonvested, Weighted-Average Grant Price Per Share, Beginning Balance	$ 36.63	$ 39.38	$ 33.72
Weighted-Average Grant Price Per Share, Granted	57.54	35.83	43.89
Weighted-Average Grant Price Per Share, Vested	37.27	35.71	41.91
Weighted-Average Grant Price Per Share, Forfeited		33.72	38.12
Nonvested, Weighted-Average Grant Price Per Share, Ending Balance	$ 51.69	$ 36.63	$ 39.38

Stock-Based Compensation - Summary of Assumptions Used to Estimate Fair Value of Each SAR (Detail) - Stock Appreciation Rights [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
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	2.00%	1.60%
Expected term (years)	5 years	5 years
Expected volatility	42.30%	42.90%

Stock-Based Compensation - SAR Activity (Detail) - Stock Appreciation Rights [Member] - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Stock Appreciation Rights Activity [Line Items]
SARs Outstanding, Beginning Balance	137,725	262,077	515,830
Granted, SARs	18,739		15,585
Exercised, SARs	(17,406)	(124,352)	(263,626)
Canceled, SARs			(5,712)
Shares Outstanding, SARs, Ending Balance	139,058	137,725	262,077
Outstanding, Weighted Average Grant Price Per Share, Beginning Balance	$ 19.57	$ 13.13	$ 13.98
Vested, SARs	139,058
Granted, Weighted Average Grant Price Per Share	$ 70.75		41.19
Exercisable, SARs	115,191
Exercised, Weighted Average Grant Price Per Share	$ 16.13	11.09	13.86
Canceled, Weighted Average Grant Price Per Share			21.94
Outstanding, Weighted Average Grant Price Per Share, Ending Balance	26.89	$ 19.57	$ 13.13
Vested, Weighted Average Grant Price Per Share	26.89
Exercisable, Weighted Average Grant Price Per Share	$ 19.12
Weighted Average Remaining Contractual Life, Outstanding	5 years 3 months 19 days
Weighted Average Remaining Contractual Life, Vested	5 years 3 months 19 days
Weighted Average Remaining Contractual Life, Exercisable	4 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding	$ 11,333,033
Aggregate Intrinsic Value, Vested	11,333,033
Aggregate Intrinsic Value, Exercisable	$ 10,282,908

Leases - Minimum Annual Payments Under Non-Cancelable Leases (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	$ 10,626
2019	9,344
2020	7,223
2021	6,716
2022	4,843
Thereafter	14,046
Total minimum lease payments	$ 52,798

Employee Benefit Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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	$ 3,000,000	$ 2,500,000	$ 2,200,000
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

Income Taxes - Income Tax Provision (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current income tax provision:
Federal	$ 41,177	$ 26,752	$ 25,105
State	5,420	2,798	2,560
Total	46,597	29,550	27,665
Deferred income tax provision:
Federal	1,177	5,217	987
State	(983)	216	37
Total	194	5,433	1,024
Total income tax provision	$ 46,791	$ 34,983	$ 28,689

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, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
U.S. Federal statutory taxes	$ 49,671	$ 35,990	$ 26,876
State and local taxes, net of U.S. Federal benefit	5,110	3,747	2,806
Permanent items	576	396	1,308
Excess tax benefits from vesting or settlement of stock compensation awards	(1,454)	(1,749)
Domestic production activities deduction	(4,376)	(2,740)	(2,262)
Federal credits	(534)	(488)	(328)
Other	(2,202)	(173)	289
Total income tax provision	$ 46,791	$ 34,983	$ 28,689

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating losses	$ 123	$ 93
Residential product warranty reserve	8,876	14,510
Stock-based compensation	1,823	2,186
Accruals not currently deductible and other	1,838	2,261
Inventories	3,783	5,785
State tax credit carryforwards	3,619	4,020
Gross deferred tax assets, before valuation allowance	20,062	28,855
Valuation allowance	(3,096)	(4,061)
Gross deferred tax assets, after valuation allowance	16,966	24,794
Deferred tax liabilities:
Depreciation and other	(18,055)	(25,688)
Gross deferred tax liabilities	(18,055)	(25,688)
Net deferred tax (liability) asset	$ (1,089)	$ (894)

Income Taxes - Additional Information (Detail)	12 Months Ended
Income Taxes - Additional Information (Detail)	Dec. 31, 2018	Dec. 31, 2017 USD ($) Tax_Positions	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Income Tax Contingency [Line Items]
Deferred tax assets, liability		$ 1,900,000
Valuation allowance		3,096,000	$ 4,061,000
Income tax expense (benefit)		$ 46,791,000	34,983,000	$ 28,689,000
Unrecognized tax benefits number of tax matters \| Tax_Positions		0
Unrecognized tax benefits related to identified uncertain tax positions		$ 0
Accounting Standards Update 2016-09 [Member]
Income Tax Contingency [Line Items]
Income tax expense (benefit)		$ (1,500,000)	$ (1,700,000)
Scenario, Forecast [Member]
Income Tax Contingency [Line Items]
Statutory tax rate, percentage	21.00%
Earliest Tax Year [Member] \| Federal Tax Jurisdiction [Member]
Income Tax Contingency [Line Items]
Tax years subject to examination		2013
Latest Tax Year [Member] \| Federal Tax Jurisdiction [Member]
Income Tax Contingency [Line Items]
Tax years subject to examination		2016

Segment Information - Additional Information (Detail) $ in Thousands	3 Months Ended								7 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jul. 31, 2017 Segment	Dec. 31, 2017 USD ($) Segment Retailer	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segment \| Segment									1	2
Number of national retailers \| Retailer										2
Net sales	$ 122,212	$ 140,194	$ 157,941	$ 144,806	$ 95,322	$ 106,168	$ 146,450	$ 131,676		$ 565,153	$ 479,616	$ 440,804
Residential [Member]
Segment Reporting Information [Line Items]
Net sales										543,300	$ 479,600	$ 440,800
Commercial [Member]
Segment Reporting Information [Line Items]
Net sales										$ 21,800

Segment Information - Details of Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net sales	$ 122,212	$ 140,194	$ 157,941	$ 144,806	$ 95,322	$ 106,168	$ 146,450	$ 131,676	$ 565,153	$ 479,616	$ 440,804
Net income (loss)	18,299	$ 20,098	$ 28,782	$ 27,949	12,629	$ 7,787	$ 23,725	$ 23,706	95,128	67,847	48,098
Depreciation and amortization									16,860	14,498	14,384
Income tax expense (benefit)									46,791	34,983	28,689
Total assets	326,227				$ 221,430				326,227	221,430
Residential [Member]
Segment Reporting Information [Line Items]
Net sales									543,300	$ 479,600	$ 440,800
Commercial [Member]
Segment Reporting Information [Line Items]
Net sales									21,800
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales									565,153
Net income (loss)									95,128
EBITDA									159,110
Depreciation and amortization									16,730
Income tax expense (benefit)									46,791
Capital expenditures									15,040
Total assets	326,227								326,227
Operating Segments [Member] \| Residential [Member]
Segment Reporting Information [Line Items]
Net sales									543,346
Net income (loss)									97,412
EBITDA									160,382
Depreciation and amortization									14,598
Income tax expense (benefit)									47,911
Capital expenditures									14,989
Total assets	247,817								247,817
Operating Segments [Member] \| Commercial [Member]
Segment Reporting Information [Line Items]
Net sales									21,807
Net income (loss)									(2,284)
EBITDA									(1,272)
Depreciation and amortization									2,132
Income tax expense (benefit)									(1,120)
Capital expenditures									51
Total assets	$ 78,410								$ 78,410

Segment Information - Schedule of Reconciliation of Net Income to EBITDA (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net income (loss)	$ 18,299	$ 20,098	$ 28,782	$ 27,949	$ 12,629	$ 7,787	$ 23,725	$ 23,706	$ 95,128	$ 67,847	$ 48,098
Interest									461	1,125	619
Taxes									46,791	34,983	28,689
Depreciation and amortization									16,860	$ 14,498	$ 14,384
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net income (loss)									95,128
Interest									461
Taxes									46,791
Depreciation and amortization									16,730
EBITDA									159,110
Operating Segments [Member] \| Residential [Member]
Segment Reporting Information [Line Items]
Net income (loss)									97,412
Interest									461
Taxes									47,911
Depreciation and amortization									14,598
EBITDA									160,382
Operating Segments [Member] \| Commercial [Member]
Segment Reporting Information [Line Items]
Net income (loss)									(2,284)
Taxes									(1,120)
Depreciation and amortization									2,132
EBITDA									$ (1,272)

Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Schedule Of Commitments And Contingencies [Line Items]
Change in warranty reserve for disclosure purposes only	$ 2.8
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
Raw Material Supply Contracts [Member]
Schedule Of Commitments And Contingencies [Line Items]
Purchase commitment	$ 47.2
Purchase commitment, due in second year	9.5
Purchase commitment, due in third year	$ 5.9

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, 2017	Dec. 31, 2016
Product Warranty Liability [Line Items]
Beginning balance	$ 37,692	$ 33,522
Provisions and changes in estimates	4,268	10,852
Settlements made during the period	(6,961)	(6,682)
Ending balance	34,999	37,692
Surface Flaking [Member]
Product Warranty Liability [Line Items]
Beginning balance	33,847	29,673
Provisions and changes in estimates		9,835
Settlements made during the period	(5,689)	(5,661)
Ending balance	28,158	33,847
Other Residential [Member]
Product Warranty Liability [Line Items]
Beginning balance	3,845	3,849
Provisions and changes in estimates	4,268	1,017
Settlements made during the period	(1,272)	(1,021)
Ending balance	$ 6,841	$ 3,845

Interim Financial Data (Unaudited) - Summary of Interim Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Abstract]
Net sales	$ 122,212	$ 140,194	$ 157,941	$ 144,806	$ 95,322	$ 106,168	$ 146,450	$ 131,676	$ 565,153	$ 479,616	$ 440,804
Gross profit	50,906	55,284	72,014	65,169	38,113	29,945	61,410	57,627	243,373	187,095	154,869
Net income	$ 18,299	$ 20,098	$ 28,782	$ 27,949	$ 12,629	$ 7,787	$ 23,725	$ 23,706	$ 95,128	$ 67,847	$ 48,098
Basic net income per share	$ 0.62	$ 0.68	$ 0.98	$ 0.95	$ 0.43	$ 0.27	$ 0.81	$ 0.80	$ 3.24	$ 2.31	$ 1.53
Basic weighted average common shares outstanding	29,412,848	29,404,049	29,389,458	29,363,210	29,318,915	29,295,284	29,264,362	29,697,722	29,392,559	29,394,559	31,350,542
Diluted net income per share	$ 0.62	$ 0.68	$ 0.97	$ 0.95	$ 0.43	$ 0.26	$ 0.80	$ 0.79	$ 3.22	$ 2.29	$ 1.52
Diluted weighted average common shares outstanding	29,611,129	29,578,216	29,550,418	29,561,406	29,543,842	29,516,718	29,477,870	29,910,292	29,575,460	29,612,669	31,682,509

Interim Financial Data (Unaudited) - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Interim Reporting [Line Items]
Tax benefit due to change in tax rate on the deferred tax assets and deferred tax liabilities		$ 1.9
Scenario, Forecast [Member]
Interim Reporting [Line Items]
Federal statutory tax rate, percentage	21.00%

Schedule II - Valuation and Qualifying Accounts and Reserves (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Warranty Reserve [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 37,692	$ 33,522	$ 33,841
Additions (Reductions) Charged to Cost and Expenses	4,268	10,852	8,515
Deductions	(6,961)	(6,682)	(8,834)
Balance at End of Period	34,999	37,692	33,522
Valuation Allowance of Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	4,061	4,582	4,465
Additions (Reductions) Charged to Cost and Expenses			117
Deductions	(965)	(521)
Balance at End of Period	$ 3,096	$ 4,061	$ 4,582

Goodwill and Other Intangible Assets - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 2.0