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Number of customer accounted for ten percent or more sales of net sales.

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Number of financial institutions where Company deposits are maintained.

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Number of largest raw material suppliers.

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Schedule of significant accounting policies.

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Valuation allowance for credit losses and disputed amounts.

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The number of years the Company warrants that its products will be free from material defects in workmanship and materials.

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Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.

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Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount by which inventory stated at last-in first-out (LIFO) is less than (in excess of) inventory stated at other inventory cost methods.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Customer Institution Supplier	Dec. 31, 2018 USD ($) Customer	Dec. 31, 2017 USD ($) Customer	Jan. 01, 2019 USD ($)
Schedule Of Significant Accounting Policies [Line Items]
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	3	2	2
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	$ (19,062)	$ (18,442)
Annual impairment test of goodwill	0	0	$ 0
Goodwill	68,500
Valuation allowance	2,988	3,015
Research and Development costs	4,500	4,200	3,800
Prepaid expenses for production costs of advertising	500	0
Branding Expenses	35,700	35,000	$ 31,000
Operating lease assets	40,049	0
Operating lease liabilities	7,079	$ 0
Unpaid Liabilities relates to property plant and equipment	$ 800
Accounting Standards Update 2016-02 [Member]
Schedule Of Significant Accounting Policies [Line Items]
Operating lease assets				$ 45,800
Operating lease liabilities				$ 47,200
Residential Use [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	25 years
Residential Use [Member] \| Transcend Enhance Select And Universal Fascia Product [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	25 years
Residential Use [Member] \| Trex Signature Railing [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
Commercial Use [Member] \| Transcend Enhance Select And Universal Fascia Product [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	10 years
Commercial Use [Member] \| Trex Signature Railing [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	25 years
Commercial Use [Member] \| Maximum [Member] \| Commercial Railing And Staging Systems [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	3 years
Commercial Use [Member] \| Minimum [Member] \| Commercial Railing And Staging Systems [Member]
Schedule Of Significant Accounting Policies [Line Items]
Warranty period	1 year
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	57.00%	42.00%	41.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer One [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	30.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Two [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	24.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer Three [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	10.00%
Raw Materials [Member] \| Supplier Concentration Risk [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	27.00%	33.00%	33.00%