Commitments and Contingencies - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Sep. 30, 2013 USD ($)	Dec. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)
Schedule Of Commitments And Contingencies [Line Items]
Charge recorded		$ 205,000	$ 1,471,000
Minimum payments remaining under the Company's lease relating to its reconsidered corporate relocation for 2017		9,013,000
Minimum payments remaining under the Company's lease relating to its reconsidered corporate relocation for 2018		8,683,000
Minimum payments remaining under the Company's lease relating to its reconsidered corporate relocation for 2019		7,573,000
Increase in warranty reserve	$ 20,000,000
Change in warranty reserve for disclosure purposes only		$ 3,000,000
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		$ 5,426,000
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
TrexTrim and Trex Reveal Railing [Member] | Residential Use [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period		25 years
TrexTrim and Trex Reveal 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]
Lease square feet | ft²		49,756
Net minimum receipts remaining under the Company's existing subleases for 2016		$ 1,100,000
Net minimum receipts remaining under the Company's existing subleases for 2017		1,200,000
Net minimum receipts remaining under the Company's existing subleases for 2018		1,300,000
Net minimum receipts remaining under the Company's existing subleases for 2019		$ 700,000
Contract Termination [Member]
Schedule Of Commitments And Contingencies [Line Items]
Lease square feet | ft²		55,047
Charge recorded		$ 200,000	$ 1,500,000
Minimum payments remaining under the Company's lease relating to its reconsidered corporate relocation for 2016		1,900,000
Minimum payments remaining under the Company's lease relating to its reconsidered corporate relocation for 2017		1,900,000
Minimum payments remaining under the Company's lease relating to its reconsidered corporate relocation for 2018		2,000,000
Minimum payments remaining under the Company's lease relating to its reconsidered corporate relocation for 2019		1,000,000
Raw Material Supply Contracts [Member]
Schedule Of Commitments And Contingencies [Line Items]
Purchase commitment		21,100,000
Purchase commitment, due in second year		9,800,000
Purchase commitment, due in third year		700,000
Purchase commitment, due in fourth year		$ 47,000