Commitments and Contingencies - Additional Information (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) ft²	Dec. 31, 2015 USD ($)
Schedule Of Commitments And Contingencies [Line Items]
Minimum payments, 2017		$ 9,606
Minimum payments, 2018		9,271
Minimum payments, 2019		8,205
Change in warranty reserve for disclosure purposes only		$ 3,400
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]
Increase in warranty reserve	$ 9,800	$ 9,835	$ 5,426
Change in percentage of annual cash outflow for surface flaking claims declined		21.00%	19.00%
Change in annual cash outflow for surface flaking claims declined		$ 1,500	$ 1,700
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
Sublease [Member]
Schedule Of Commitments And Contingencies [Line Items]
Net minimum receipts remaining under the Company's existing subleases for 2017		$ 1,300
Net minimum receipts remaining under the Company's existing subleases for 2018		1,300
Net minimum receipts remaining under the Company's existing subleases for 2019		$ 700
Contract Termination [Member]
Schedule Of Commitments And Contingencies [Line Items]
Lease square feet | ft²		55,047
Minimum payments, 2017		$ 1,900
Minimum payments, 2018		2,000
Minimum payments, 2019		1,000
Waste Wood And Pe Material Supply Contracts [Member]
Schedule Of Commitments And Contingencies [Line Items]
Purchase commitment		20,200
Purchase commitment, due in second year		3,200
Purchase commitment, due in third year		350
Purchase commitment, due in fourth year		$ 50