v3.7.0.1
Document and Entity Information - shares
6 Months Ended
Jun. 30, 2017
Jul. 18, 2017
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2017  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q2  
Trading Symbol TREX  
Entity Registrant Name TREX CO INC  
Entity Central Index Key 0001069878  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   29,406,092