Trex (TREX) 10-K 22 Feb 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Jan. 29, 2021	Jun. 30, 2020
Cover [Abstract]
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Type	10-K
Document Fiscal Period Focus	FY
Entity Central Index Key	0001069878
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity Registrant Name	TREX CO INC
Document Period End Date	Dec. 31, 2020
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Trading Symbol	TREX
Entity Shell Company	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		115,799,503
Entity File Number	001-14649
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	54-1910453
Entity Address, Address Line One	160 Exeter Drive
Entity Address, City or Town	Winchester
Entity Address, Postal Zip Code	22603-8605
Entity Address, State or Province	VA
City Area Code	540
Local Phone Number	542-6300
Title of 12(b) Security	Common stock
Security Exchange Name	NYSE
Document Annual Report	true
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 7.5
ICFR Auditor Attestation Flag	true

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net sales	$ 880,831	$ 745,347	$ 684,250
Cost of sales	521,374	438,844	389,356
Gross profit	359,457	306,503	294,894
Selling, general and administrative expenses	125,822	118,304	118,225
Income from operations	233,635	188,199	176,669
Interest (income) expense, net	(999)	(1,503)	(192)
Income before income taxes	234,634	189,702	176,861
Provision for income taxes	59,003	44,964	42,289
Net income	$ 175,631	$ 144,738	$ 134,572
Basic earnings per common share	$ 1.52	$ 1.24	$ 1.15
Basic weighted average common shares outstanding	115,888,859	116,861,194	117,479,340
Diluted earnings per common share	$ 1.51	$ 1.24	$ 1.14
Diluted weighted average common shares outstanding	116,252,866	117,315,498	118,134,604
Comprehensive income	$ 175,631	$ 144,738	$ 134,572

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 121,701	$ 148,833
Accounts receivable, net	106,748	78,462
Inventories	68,238	56,106
Prepaid expenses and other assets	25,310	19,803
Total current assets	321,997	303,204
Property, plant and equipment, net	336,537	171,300
Goodwill and other intangible assets, net	73,665	74,084
Operating lease assets	34,382	40,049
Other assets	3,911	3,602
Total Assets	770,492	592,239
Current Liabilities:
Accounts payable	38,622	15,227
Accrued expenses and other liabilities	62,331	58,265
Accrued warranty	5,400	5,178
Total current liabilities	106,353	78,670
Operating lease liabilities	28,579	34,242
Non-current accrued warranty	24,073	20,317
Deferred income taxes	22,956	9,831
Other long-term liabilities		4
Total Liabilities	181,961	143,064
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, 180,000,000 shares authorized; 140,577,005 and 140,374,926 shares issued and 115,799,503 and 116,481,442 shares outstanding at December 31, 2020 and 2019, respectively	1,406	1,404
Additional paid-in capital	126,087	123,294
Retained earnings	737,311	561,680
Treasury stock, at cost, 24,777,502 and 23,893,484 shares at December 31, 2020 and 2019, respectively	(276,273)	(237,203)
Total Stockholders' Equity	588,531	449,175
Total Liabilities and Stockholders' Equity	$ 770,492	$ 592,239

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
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	180,000,000	180,000,000
Common stock, shares issued	140,577,005	140,374,926
Common stock, shares outstanding	115,799,503	116,481,442
Treasury stock, shares	24,777,502	23,893,484

Statements of Changes in Stockh

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, 2017	$ 231,250	$ 1,396	$ 120,996	$ 282,370	$ (173,512)
Beginning Balance, Shares at Dec. 31, 2017		117,713,720			21,974,724
Net income	134,572			134,572
Employee stock plans	882	$ 2	880
Employee stock plans, Shares		126,896
Shares withheld for taxes on awards	(4,695)		(4,695)
Shares withheld for taxes on awards, Shares		(26,056)
Stock-based compensation	6,345	$ 2	6,343
Stock-based compensation, Shares		207,388
Repurchases of common stock	(25,391)				$ (25,391)
Repurchases of common stock, Shares		(918,642)			918,642
Ending Balance at Dec. 31, 2018	342,963	$ 1,400	123,524	416,942	$ (198,903)
Ending Balance, Shares at Dec. 31, 2018		117,103,306			22,893,366
Net income	144,738			144,738
Employee stock plans	1,089	$ 2	1,087
Employee stock plans, Shares		154,282
Shares withheld for taxes on awards	(8,245)		(8,245)
Shares withheld for taxes on awards, Shares		(216,756)
Stock-based compensation	6,930	$ 2	6,928
Stock-based compensation, Shares		440,728
Repurchases of common stock	(38,300)				$ (38,300)
Repurchases of common stock, Shares		(1,000,118)			1,000,118
Ending Balance at Dec. 31, 2019	449,175	$ 1,404	123,294	561,680	$ (237,203)
Ending Balance, Shares at Dec. 31, 2019		116,481,442			23,893,484
Net income	175,631			175,631
Employee stock plans	1,446		1,446
Employee stock plans, Shares		68,061
Shares withheld for taxes on awards	(5,784)		(5,784)
Shares withheld for taxes on awards, Shares		(111,433)
Stock-based compensation	7,133	$ 2	7,131
Stock-based compensation, Shares		245,451
Repurchases of common stock	(39,070)				$ (39,070)
Repurchases of common stock, Shares		(884,018)			884,018
Ending Balance at Dec. 31, 2020	$ 588,531	$ 1,406	$ 126,087	$ 737,311	$ (276,273)
Ending Balance, Shares at Dec. 31, 2020		115,799,503			24,777,502

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net income	$ 175,631	$ 144,738	$ 134,572
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	17,939	14,031	16,597
Deferred income taxes	13,125	7,706	1,037
Stock-based compensation	7,131	6,930	6,344
(Gain) loss on disposal of property, plant and equipment	(56)	285	47
Other non-cash adjustments	51	(218)	(406)
Changes in operating assets and liabilities:
Accounts receivable	(28,286)	12,701	(24,281)
Inventories	(12,132)	1,695	(23,276)
Prepaid expenses and other assets	(358)	(1,652)	(613)
Accounts payable	11,353	(16,666)	21,131
Accrued expenses and other liabilities	7,655	(10,823)	5,040
Income taxes receivable/payable	(4,759)	(2,375)	1,929
Net cash provided by operating activities	187,294	156,352	138,121
Investing Activities
Expenditures for property, plant and equipment and intangibles	(172,823)	(67,265)	(33,816)
Proceeds from sales of property, plant and equipment	2,165	21	83
Net cash used in investing activities	(170,658)	(67,244)	(33,733)
Financing Activities
Borrowings under line of credit	276,000	89,500	172,250
Principal payments under line of credit	(276,000)	(89,500)	(172,250)
Repurchases of common stock	(44,854)	(46,545)	(30,085)
Proceeds from employee stock purchase and option plans	1,446	1,089	882
Financing costs	(360)	(518)
Net cash used in financing activities	(43,768)	(45,974)	(29,203)
Net (decrease) increase in cash and cash equivalents	(27,132)	43,134	75,185
Cash and cash equivalents, beginning of period	148,833	105,699	30,514
Cash and cash equivalents, end of period	121,701	148,833	105,699
Supplemental Disclosure:
Cash paid for interest	187	321	662
Cash paid for income taxes, net	$ 50,744	$ 39,612	$ 48,238

Business and Organization

Business and Organization	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Organization	1. BUSINESS AND ORGANIZATION Trex Company, Inc. (together with its wholly-owned subsidiary, the Company), a Delaware corporation, was incorporated on September 4, 1998. The Company operates in two reportable segments, Trex Residential Products (Trex Residential) and Trex Commercial Products (Trex Commercial). The Company’s principal business based on net sales is the manufacture and distribution of Trex Residential wood and plastic composite products, as well as related accessories, primarily for residential decking and railing applications. Trex Commercial designs, engineers and markets modular and architectural railing and staging systems for the commercial and multi-family market, including sports stadiums and performing arts venues. The principal executive offices are located at 160 Exeter Drive, Winchester, Virginia 22603, and the telephone number at that address is (540) 542-6300.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
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 and its wholly-owned subsidiary, Trex Commercial Products, Inc. Intercompany accounts and transactions have been eliminated in consolidation. 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 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, 2020, 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 recognized at the amount of revenue recognized on each shipment for Trex Residential products and for satisfied performance obligations for Trex Commercial products as the Company has an unconditional right to consideration from the customer and payment is due based solely on the passage of time. An estimate of expected credit losses is recognized as a valuation allowance and adjusted each reporting period. The estimate is based on the current expected credit loss model and is determined using an aging schedule, including past events, current conditions and reasonable and supportable forecasts about the future. There was no material valuation allowance recorded as of December 31, 2020 and December 31, 2019. In the years ended December 31, 2020, 2019, and 2018 sales to certain customers of Trex Residential accounted for 10% or more of the Company’s total net sales. For the year ended December 31, 2020, three customers represented approximately 56% of the Company’s total net sales. For the year ended December 31, 2019, For each year ended December 31, 2020, 2019, and 2018, approximately 28%, 27%, and 33%, respectively, of the Company’s materials purchases at Trex Residential were purchased from its Inventories Inventories for the Company’s composite decking and railing products are valued at the lower of cost (last-in, first-out, A majority of the Company’s products at Trex Residential 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 railing and staging products at Trex Commercial for the commercial and multi-family market are valued at the lower of cost (first-in, first-out Work-in 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. Unpaid liabilities related to property, plant and equipment are included in accounts payable and were $12.9 million and $0.8 million at December 31, 2020 and December 31, 2019, respectively. Cash flows for capital expenditures as reported in cash flows from investing activities in the Consolidated Statements of Cash Flows are adjusted to exclude unpaid amounts accrued at period end. 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 Leases The Company leases office space, storage warehouses and certain plant equipment under various operating leases. At inception of an arrangement, the Company evaluates, among other things, whether it has the right to control the use of an identified asset in order to determine if the arrangement is or contains a lease. Operating leases are included in operating lease right-of-use non-lease non-lease 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 The Company assigned its goodwill to reporting units and tests each reporting unit’s goodwill for impairment at least on an annual basis, or more frequently if an event occurs or circumstances change in the interim that indicate the carrying amount of reporting unit goodwill exceeds the implied fair value of that goodwill. 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 operating segment management, at a level below the Company’s chief operating decision maker, regularly reviews the operating results of the reporting unit. 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. In testing for goodwill impairment, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount, including goodwill. If the qualitative assessment indicates that the carrying amount of the reporting unit exceeds its fair value, including goodwill, the Company is then required to perform a quantitative goodwill impairment test. The quantitative goodwill impairment test, used to identify both the existence of impairment and the amount of impairment loss, compares the fair value of a reporting unit with its carrying amount, including goodwill. The fair value of a reporting unit refers to the price that would be received to sell the unit as a whole in an orderly transaction between market participants at the measurement date. If the carrying amount of a reporting unit exceeds its fair value, an impairment loss is recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. The Company measures fair value of the reporting units based on a present value of future cash flows (discounted cash flows model) 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, 2020, 2019, and 2018, the Company completed its annual impairment test of goodwill utilizing the qualitative assessment and concluded it was not more likely than Product Warranty The Company warrants that its Trex 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 ® ® ® ® 25 one available actual 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 Effective January 1, 2018, the Company retrospectively adopted the requirements of Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) 2014-09, Trex Residential Products. low-maintenance, eco-friendly Trex Commercial Products. Trex Commercial satisfies its performance obligation over time catch-up 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. As of December 31, 2020, the Company has a valuation allowance of $2.8 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, 2020, 2019, and 2018, research and development costs were $3.4 million, $4.5 million, and $4.2 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. Production costs are deferred and recognized as expense in the period that the related advertisement is first used. At December 31, 2020 and December 31, 2019 $0.01 million and $0.5 million was included in prepaid expenses for production costs, respectively. For the years ended December 31, 2020, 2019, and 2018, branding expenses, including advertising expenses as described above, were $31.7 million, $35.7 million, and $35.0 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, and debt to approximate the fair value of the respective assets and liabilities on the Consolidated Balance Sheets at December 31, 2020 and 2019. Recently Adopted Accounting Standards In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-15, Intangibles – Goodwill and Other – Internal-Use 350-40): internal-use In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses in Financial Instruments New Accounting Standards Not Yet Adopted In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting reporting burdens as the market transitions from the London Interbank Offered Rate and other interbank offered rates to alternative reference rates. The new guidance allows entities to elect not to apply certain modification accounting requirements, if certain criteria are met, to contracts affected by what the guidance calls reference rate reform. An entity that makes this election would consider changes in reference rates and other contract modifications related to reference rate reform to be events that do not require contract remeasurement at the modification date or reassessment of a previous accounting determination. The ASU notes that changes in contract terms that are made to affect the reference rate reform transition are considered related to the replacement of a reference rate if they are not the result of a business decision that is separate from or in addition to changes to the terms of a contract to affect that transition. The guidance is effective upon issuance and generally can be applied as of March 12, 2020 through December 31, 2022. The Company does not expect adoption of the guidance to have a material effect on its consolidated financial statements. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes step-up

Inventories

Inventories	12 Months Ended
	Dec. 31, 2020
Inventory Disclosure [Abstract]
Inventories	3. INVENTORIES Inventories at LIFO value consist of the following as of December 31 (in thousands): 2020 2019 Finished goods $ 39,048 $ 42,281 Raw materials 44,475 31,686 Total FIFO inventories 83,523 73,967 Reserve to adjust inventories to LIFO value (16,821 ) (19,062 ) Total LIFO inventories $ 66,702 $ 54,905 Inventory related to Trex Residential composite decking and railing products is stated at the lower of LIFO cost or market. The Company periodically reviews its inventory for slow moving or obsolete items and writes down the related products to estimated market. 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 Inventories valued at lower of cost (FIFO method) and net realizable value as of December 31, 2020 and December 31, 2019, were $1.5 million and $1.2 million, respectively, consisting primarily of raw materials. The Company utilizes the FIFO method of accounting related to its Trex Commercial products.

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets	12 Months Ended
	Dec. 31, 2020
Text Block [Abstract]
Prepaid Expenses and Other Assets	4. PREPAID EXPENSES AND OTHER ASSETS Prepaid expenses and other assets consist of the following as of December 31 (in thousands): 2020 2019 Prepaid expenses $ 7,285 $ 8,282 Revenues in excess of billings 6,612 6,664 Contract retainage 2,267 1,832 Income tax receivable 7,823 2,675 Other 1,323 350 Total prepaid expenses and other assets $ 25,310 $ 19,803

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets, Net	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets, Net	5. GOODWILL AND OTHER INTANGIBLE ASSETS, NET The carrying amount of goodwill by reportable segment at December 31, 2020 and 2019 was $14.2 million for Trex Residential and $54.3 million for Trex Commercial. The Company’s intangible assets consist of domain names purchased in May 2018. At December 31, 2020 and 2019, intangible assets were $6.3 million, and accumulated amortization was $1.1 million and $0.7 million, respectively. 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 basis over 15 years, which approximates the pattern in which the economic benefits are expected to be received. The Company evaluates the recoverability of intangible assets periodically and considers events or circumstances that may warrant revised estimates of useful lives or that may indicate an impairment. Intangible asset amortization expense for the years ended December 31, 2020, December 31, 2019 and December 31, 2018, was $0.4 million, $0.4 million and $3.1 million, respectively. Intangible asset amortization expense for the year ended December 31, 2018 included amortization expense for customer backlog and trade names and trademarks, which were fully amortized as of December 31, 2018.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	6. PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consist of the following as of December 31 (in thousands): 2020 2019 Machinery and equipment $ 312,870 $ 248,633 Building and improvements 61,860 51,547 Forklifts and tractors 16,003 10,870 Computer equipment 11,948 10,647 Furniture and fixtures 1,534 1,441 Construction in process 157,465 59,257 Land 11,351 11,417 Total property, plant and equipment 573,031 393,812 Accumulated depreciation (236,494 ) (222,512 ) Total property, plant and equipment, net $ 336,537 $ 171,300 The Company had construction in process as of December 31, 2020 of approximately $157.5 million. The Company expects that the construction in process will be completed and put into service in the year ending December 31, 2021. Depreciation expense for the years ended December 31, 2020, 2019, and 2018, totaled $17.5 million, $13.6 million, and $13.4 million, respectively.

Accrued Expenses and Other Liab

Accrued Expenses and Other Liabilities	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued Expenses and Other Liabilities	7. ACCRUED EXPENSES AND OTHER LIABILITIES Accrued expenses and other liabilities consist of the following as of December 31 (in thousands): 2020 2019 Sales and marketing $ 22,938 $ 28,402 Compensation and benefits 21,156 13,475 Operating lease liabilities 6,708 7,079 Manufacturing costs 3,641 2,564 Customer deposits 1,174 2,905 Billings in excess of revenues 1,244 816 Other 5,470 3,024 Total accrued expenses $ 62,331 $ 58,265

Debt

Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt	8. DEBT The Company’s debt consists of a revolving credit facility. At December 31, 2020 and 2019, the Company had no outstanding indebtedness. Available borrowing capacity at December 31, 2020, was $300 million. Revolving Credit Facility On November 5, 2019, the Company entered into a Fourth Amended and Restated Credit Agreement (Fourth Amended Credit Agreement) as borrower, Trex Commercial Products, Inc., as guarantor; Bank of America, N.A. as a Lender, Administrative Agent, Swing Line Lender and L/C Issuer; and certain other lenders including Wells Fargo Bank, N.A., who is also Syndication Agent, and Truist Bank, arranged by BOA Securities, Inc., as Sole Lead Arranger and Sole Bookrunner, to amend and restate the Third Amended and Restated Credit Agreement (Third Amended Credit Agreement), dated as of January 12, 2016, as amended. The Fourth Amended Credit Agreement provides 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 November 5, 2024. On May 26, 2020, the Company entered into a First Amendment to the Original Credit Agreement (the First Amendment) to provide for an additional $100 million line of credit through May 26, 2022. The purpose of the additional $100 million line of credit is primarily to reduce risk associated with the COVID-19 The Company entered into the First Amendment, as borrower; Trex Commercial Products, Inc. (TCP), as guarantor; Bank of America, N.A. (BOA), as a Lender, Administrative Agent, Swing Line Lender and L/C Issuer; and certain other lenders including Wells Fargo Bank, N.A. (Wells Fargo), who is also Syndication Agent; Truist Bank (Truist); and Regions Bank (Regions) (each, a Lender and collectively, the Lenders), arranged by BofA Securities, Inc. as Sole Lead Arranger and Sole Bookrunner. The First Amendment further provides that the New Credit Agreement is amended and restated by changing Schedule 2.01 to add applicable Lender percentages related to the Revolving B Commitment for BOA of 47.5%, Wells The Notes and interest rates for the Revolving A Commitments remained unchanged and are the same as previously disclosed. The Notes for Revolving A Commitments and Revolving B Commitments provide the Company, in the aggregate, the ability to borrow an amount up to the respective Revolving A Loan Limit and Revolving B Loan Limit during the respective Revolving A Term and Revolving B Term. The Company is not obligated to borrow any amount under either the Revolving A Loan or the Revolving B Loan. Within either the Revolving A Loan or the Revolving B Loan, the Company may borrow, repay and reborrow at any time or from time to time while the respective Revolving A Loan or Revolving B Loan remains in effect. Base Rate Loans (as defined in the Fourth Amended Credit Agreement) under the Revolving Loans and the Swing Line Loans accrue interest at the Base Rate plus the Applicable Rate (as defined in the Fourth Amended Credit Agreement) and Eurodollar Rate Loans for the Revolving Loans and Swing Line Loans accrue interest at the Adjusted London InterBank Offered Rate plus the Applicable Rate (as defined in the Fourth Amended Credit Agreement). 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%. The Applicable Rate for Revolving B Commitments means the following percentages per annum, based upon the Consolidated Debt to Consolidated EBITDA Ratio as set forth in the most recent Compliance Certificate received by BOA as the Administrative Agent and as set forth in the New Credit Agreement: Pricing Tier Consolidated Debt to EBITDA Ratio Eurodollar Rate Base Rate Loans Revolving B 1 > 2.50:1.00 2.75 % 1.75 % 0.60 % 2 < 2.50:1.00 but > 2.00:1.00 2.50 % 1.50 % 0.55 % 3 < 2.00:1.00 but > 1.50:1.00 2.25 % 1.25 % 0.50 % 4 < 1.50:1.00 1.80 % 0.80 % 0.45 % Compliance with Debt Covenants and Restrictions Pursuant to the terms of the Fourth Amended Credit Agreement, the Company is subject to certain loan compliance covenants. The Company was in compliance with all covenants as of December 31, 2020. 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.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	9. LEASES For the years ended December 31, 2020 and December 31, 2019, total operating lease cost was $8.5 million and $8.4 million, respectively. The weighted average remaining lease term at December 31, 2020 and December 31, 2019 was 5.6 years and 6.5 years, respectively. The weighted average discount rate at December 31, 2020 and December 31, 2020 was 3.47% and 3.66%, respectively. The following table includes supplemental cash flow information for the years ended December 31, 2020 and December 31, 2019 and supplemental balance sheet information at December 31, 2020 and December 31, 2019 related to operating leases: For the Year Ended December 31 Supplemental Cash Flow Information 2020 2019 Cash paid for amounts included in the measurement of operating lease liabilities $ 8,736 $ 8,479 Operating ROU assets obtained in exchange for lease liabilities $ 1,427 $ 1,319 Supplemental Balance Sheet Information December 31, 2020 December 31, Operating lease ROU assets $ 34,382 $ 40,049 Operating lease liabilities: Accrued expenses and other current liabilities $ 6,708 $ 7,079 Operating lease liabilities 28,579 34,242 Total operating lease liabilities $ 35,287 $ 41,321 The following table summarizes maturities of operating lease liabilities at December 31, 2020 (in thousands): Maturities of operating lease liabilities 2021 $ 7,835 2022 7,345 2023 6,608 2024 6,265 2025 4,480 Thereafter 6,599 Total lease payments 39,132 Less imputed interest (3,845 ) Total operating liabilities $ 35,287

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2020
Investments, All Other Investments [Abstract]
Financial Instruments	10. 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, and debt to approximate the fair value of the respective assets and liabilities on the Consolidated Balance Sheets at December 31, 2020 and 2019.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 Numerator: Net income $ 175,631 $ 144,738 $ 134,572 Denominator: Basic weighted average shares outstanding 115,888,859 116,861,194 117,479,340 Effect of dilutive securities: Stock appreciation rights 192,579 248,850 353,400 Restricted stock 171,428 205,454 301,864 Diluted weighted average shares outstanding 116,252,866 117,315,498 118,134,604 Basic earnings per share $ 1.52 $ 1.24 $ 1.15 Diluted earnings per share $ 1.51 $ 1.24 $ 1.14 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. Year Ended December 31, 2020 2019 2018 Restricted stock — — 428 Stock appreciation rights 14,697 41,540 26,694 Stock Repurchase Program On February 16, 2018, the Board of Directors adopted a stock repurchase program of up to 11.6 million shares of the Company’s outstanding common stock (Stock Repurchase Program). On March 12, 2020, the Company suspended repurchases of its common stock under the Stock Repurchase Program due to the volatility and uncertainty in the stock market associated with the COVID-19 Amendment of Restated Certificate of Incorporation At the annual meeting of stockholders of the Company held on April 29, 2020, the Company’s stockholders approved an amendment of the Company’s Restated Certificate of Incorporation (Amendment), effective as of April 29, 2020. The Company’s Board of Directors unanimously approved the Amendment on February 19, 2020, subject to stockholder approval. The Amendment increases the number of shares of common stock, par value $0.01 per share, that the Company is authorized to issue from 120 million shares to 180 million shares. Stock Split On July 29, 2020, the Company’s Board of Directors approved a two-for-one

Revenue From Contracts With Cus

Revenue From Contracts With Customers	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue From Contracts With Customers	12. REVENUE FROM CONTRACTS WITH CUSTOMERS Topic 606 provides a single, comprehensive model for revenue recognition arising from contracts with customers. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in Topic 606. A contract’s transaction price is allocated to each distinct performance obligation and revenue is recognized when or as the Company satisfies the performance obligation. Revenue is recognized at an amount that reflects the consideration to which the entity expects to be entitled in exchange for transferring control of the goods or services to a customer. Trex Residential Products Trex Residential principally generates revenue from the manufacture and sale of its high-performance, low-maintenance, eco-friendly For each product shipped, the transaction price by product is specified in the purchase order. The Company recognizes revenue on the transaction price less any amount offered under a sales incentive program. The Company recognizes an account receivable for the amount of revenue recognized as it has an unconditional right to consideration at the time of shipment and payment from the customer is due based solely on the passage of time. The Company receives payments from its customers based on the payment terms applicable to each individual contract and the customer pays in accordance with the billing terms specified in the purchase order, which is less than one year. The related accounts receivables are included in “Accounts receivable, net” in the Consolidated Balance Sheets. Trex Residential may offer various sales incentive programs throughout the year. It estimates the amount of sales incentive to allocate to each performance obligation, or product shipped, based on direct sales to the customer. The estimate is updated each reporting period and any changes are allocated to the performance obligations on the same basis as at inception. Changes in estimate allocated to a previously satisfied performance obligation are recognized as a reduction of revenue in the period in which the change occurs under the cumulative catch-up Trex Residential pays commissions to certain employees. However, the sales commissions are not directly attributable to identifiable contracts, are discretionary in nature and are based on other factors not related to obtaining a contract, such as individual performance, profitability of the entity, annual sales targets, etc. These costs are included in selling, general and administrative expenses as incurred. Trex Residential does not grant contractual product return rights to customers other than pursuant to its assurance product warranty (see related disclosure on product warranties in Note 18, “Commitments and Contingencies”. Trex Residential accounts for all shipping and handling fees invoiced to the customer in net sales and the related costs in cost of sales. Trex Commercial Products Trex Commercial generates revenue from the manufacture and sale of its modular and architectural railing and staging systems. All of its revenues are from fixed-price contracts with customers. Trex Commercial contracts have a single performance obligation as the promise to transfer the individual goods or services is not separately identifiable from other promises in the contract and is, therefore, not distinct. Trex Commercial satisfies its performance obligation over time as work progresses because control is transferred continuously to its customers. Revenue and estimated profit is recognized over time based on the proportion of actual costs incurred to date relative to total estimated costs at completion to measure progress toward satisfying the performance obligation. Incurred costs represent work performed, which corresponds with, and thereby best depicts, the transfer of control to the customer. Incurred costs include all direct material, labor, subcontract and certain indirect costs. The Company reviews and updates its estimates regularly and recognizes adjustments in estimated profit on contracts under the cumulative catch-up The Company recognizes an account receivable for satisfied performance obligations as it has an unconditional right to consideration and payment from the customer is due based solely on the passage of time. The Company receives payments from its customers on the accounts receivable based on the payment terms applicable to each individual contract and the customer pays in less than one year. Accounts receivables are included in “Accounts receivable, net” in the Consolidated Balance Sheets. In addition, the timing of revenue recognition, billings and cash collections may result in revenues in excess of billings and contract retainage (contract assets), and billings in excess of revenues and customer deposits (contract liabilities). These assets and liabilities are reported on a contract-by-contract Trex Commercial pays sales commissions that are directly attributable to identifiable contracts to certain of its employees. If the amortization period of the commission is one year or less, then the Company recognizes the commission expense as incurred. Otherwise, the Company capitalizes the commission and amortizes it on a straight-line basis over the life of the contract. Trex Commercial does not grant contractual product return rights to customers other than pursuant to its assurance product warranty. All shipping and handling fees invoiced to the customer are included in net sales and the related costs are included in cost of sales. For each year in the three years ended December 31, 2020, net sales were disaggregated in the following tables by (1) market (2) timing of revenue recognition, and (3) type of contract. The tables also include a reconciliation of the respective disaggregated net sales with the Company’s reportable segments (in thousands): Year Ended December 31, 2020 Reportable Segment Trex Trex Total Timing of Revenue Recognition and Type of Contract Products transferred at a point in time and variable consideration contracts $ 827,792 $ — $ 827,792 Products transferred over time and fixed price contracts — 53,039 53,039 $ 827,792 $ 53,039 $ 880,831 Year Ended December 31, 2019 Reportable Segment Trex Trex Total Timing of Revenue Recognition and Type of Contract Products transferred at a point in time and variable consideration contracts $ 694,267 $ — $ 694,267 Products transferred over time and fixed price contracts — 51,080 51,080 $ 694,267 $ 51,080 $ 745,347 Year Ended December 31, 2018 Reportable Segment Trex Trex Total Timing of Revenue Recognition and Type of Contract Products transferred at a point in time and variable consideration contracts $ 613,229 $ — $ 613,229 Products transferred over time and fixed price contracts — 71,021 71,021 $ 613,229 $ 71,021 $ 684,250

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2020
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	13. 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 25,680,000 and as of December 31, 2020, the total number of shares available for future issuance was 11,253,930. 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, 2020 2019 2018 Time-based restricted stock and restricted stock units $ 3,219 $ 3,676 $ 2,687 Performance-based restricted stock and restricted stock units 2,881 2,399 3,144 Stock appreciation rights 648 662 370 Employee stock purchase plan 383 193 143 Total stock-based compensation $ 7,131 $ 6,930 $ 6,344 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, 2020, 2019 and 2018 was $6.1 million, $6.0 million and $5.1 million, respectively. At December 31, 2020, there was $2.9 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 1.7 years. Time-based restricted stock and restricted stock unit activity under the Plan and all predecessor stock incentive plans is as follows: Time-based Weighted-Average Nonvested at December 31, 2017 306,236 $ 13.45 Granted 174,528 $ 27.36 Vested (169,100 ) $ 13.33 Forfeited (568 ) $ 17.53 Nonvested at December 31, 2018 311,096 $ 21.34 Granted 71,300 $ 38.12 Vested (162,650 ) $ 18.67 Forfeited (1,280 ) $ 31.17 Nonvested at December 31, 2019 218,466 $ 28.75 Granted 54,406 $ 53.97 Vested (111,036 ) $ 30.94 Forfeited (1,114 ) $ 40.34 Nonvested at December 31, 2020 160,722 $ 35.68 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 Performance-based restricted stock activity under the Plan is as follows: Performance-based Weighted- Nonvested at December 31, 2017 233,316 $ 12.93 Granted 161,140 $ 17.63 Vested (212,044 ) $ 11.76 Forfeited — $ — Nonvested at December 31, 2018 182,412 $ 18.43 Granted 164,270 $ 23.82 Vested (222,004 ) $ 15.55 Forfeited (1,022 ) $ 29.23 Nonvested at December 31, 2019 123,656 $ 30.67 Granted 78,404 $ 39.60 Vested (128,762 ) $ 28.87 Forfeited (728 ) $ 41.12 Nonvested at December 31, 2020 72,570 $ 43.42 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 forfeitures as they occur. The Company recognizes compensation cost on a straight-line basis over the vesting period for the award. As of December 31, 2020, there was $0.6 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. For SARs issued in the years ended December 31, 2020, December 31, 2019 and December 31, 2018, respectively, the assumptions shown in the following table were used: Year Ended December 31, 2020 2019 2018 Dividend yield 0 % 0 % 0 % Average risk-free interest rate 1.3 % 2.5 % 2.7 % Expected term (years) 5 5 5 Expected volatility 38.3 % 39.1 % 40.5 % Dividend Yield. Average Risk-Free Interest Rate. Expected Term. Expected Volatility. The weighted-average grant date fair value of SARs granted during the years ended December 31, 2020, December 31, 2019 and December 31, 2018 was $17.81, $14.78 and $11.05, respectively. SAR activity under the Plan and all predecessor stock incentive plans is as follows: SARs Weighted-Average Weighted-Average Aggregate Outstanding at December 31, 2017 556,232 $ 6.73 Granted 42,520 $ 28.30 Exercised (121,800 ) $ 2.64 Canceled — $ — Outstanding at December 31, 2018 476,952 $ 9.63 Granted 49,072 $ 38.85 Exercised (217,528 ) $ 6.95 Canceled (4,458 ) $ 38.85 Outstanding at December 31, 2019 304,038 $ 15.79 Granted 43,830 $ 50.39 Exercised (54,592 ) $ 9.41 Canceled — $ — Outstanding at December 31, 2020 293,276 $ 22.15 5.4 $ 18,058,138 Vested at December 31, 2020 237,323 $ 17.05 4.7 $ 15,821,712 Exercisable at December 31, 2020 237,323 $ 17.05 4.7 $ 15,821,712 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

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
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 and it matches qualifying employee contributions. The Company’s contributions to the plans totaled $5.7 million, $4.6 million and $4.2 million for the years ended December 31, 2020, 2019 and 2018, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	15. INCOME TAXES Income tax provision (benefit) consists of the following (in thousands): Year Ended December 31, 2020 2019 2018 Current income tax provision: Federal $ 35,423 $ 30,306 $ 33,578 State 10,455 6,952 7,674 45,878 37,258 41,252 Deferred income tax provision: Federal 12,603 6,928 988 State 522 778 49 13,125 7,706 1,037 Total income tax provision $ 59,003 $ 44,964 $ 42,289 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, 2020 2019 2018 U.S. Federal statutory taxes $ 49,273 $ 39,838 $ 37,141 State and local taxes, net of U.S. Federal benefit 10,641 8,412 7,716 Permanent items 1,198 1,266 470 Excess tax benefits from vesting or settlement of stock compensation awards (1,635 ) (3,540 ) (2,368 ) Federal credits (565 ) (654 ) (662 ) Other 91 (358 ) (8 ) Total income tax provision $ 59,003 $ 44,964 $ 42,289 Deferred tax assets and liabilities consist of the following (in thousands): As of December 31, 2020 2019 Deferred tax assets: Net operating losses $ 43 $ 88 Residential product warranty reserve 7,532 6,486 Stock-based compensation 1,071 1,055 Accruals not currently deductible and other 2,041 2,245 Inventories 5,548 5,780 Operating lease liability 9,081 10,618 State tax credit carryforwards 3,345 3,461 Gross deferred tax assets, before valuation allowance 28,661 29,733 Valuation allowance (2,775 ) (2,988 ) Gross deferred tax assets, after valuation allowance 25,886 26,745 Deferred tax liabilities: Depreciation (29,792 ) (17,267 ) Operating lease right-of-use (8,755 ) (10,162 ) Goodwill amortization (5,775 ) (4,782 ) Inventories and other (4,520 ) (4,365 ) Gross deferred tax liabilities (48,842 ) (36,576 ) Net deferred tax liability $ (22,956 ) $ (9,831 ) 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. In accordance with accounting standards, 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. As of December 31, 2020, the Company had a valuation allowance of $2.8 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. 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, 2020, 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, 2020, for certain tax jurisdictions, tax years 2016 through 2019

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Segment Information	16. SEGMENT INFORMATION The Company operates in two reportable segments: • Trex Residential manufactures composite decking and railing and related products marketed under the brand name Trex ® • Trex Commercial designs, engineers, and markets modular and architectural railing and staging systems for commercial and multi-family market, 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. The Company’s reportable 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. Segment Data (in thousands): Net Sales Net Income EBITDA Depreciation Income Tax Capital Total Assets December 31, 2020 Trex Residential $ 827,792 $ 171,197 $ 244,817 $ 17,131 $ 57,488 $ 171,784 $ 676,948 Trex Commercial 53,039 4,434 6,758 809 1,515 1,039 93,544 Total $ 880,831 $ 175,631 $ 251,575 $ 17,940 $ 59,003 $ 172,823 $ 770,492 December 31, 2019 Trex Residential $ 694,267 $ 142,811 $ 199,020 $ 13,413 $ 44,292 $ 65,399 $ 503,883 Trex Commercial 51,080 1,927 3,210 618 672 1,866 88,356 Total $ 745,347 $ 144,738 $ 202,230 $ 14,031 $ 44,964 $ 67,265 $ 592,239 December 31, 2018 Trex Residential $ 613,229 $ 131,823 $ 186,268 $ 13,216 $ 41,421 $ 31,392 $ 380,682 Trex Commercial 71,021 2,749 6,868 3,251 868 2,424 84,440 Total $ 684,250 $ 134,572 $ 193,136 $ 16,467 $ 42,289 $ 33,816 $ 465,122 Reconciliation of Net Income (Loss) to EBITDA (in thousands): Net Income Interest Income Tax Depreciation EBITDA December 31, 2020 Trex Residential $ 171,197 $ (999 ) $ 57,488 $ 17,131 $ 244,817 Trex Commercial 4,434 — 1,515 809 6,758 Total $ 175,631 $ (999 ) $ 59,003 $ 17,940 $ 251,575 December 31, 2019 Trex Residential $ 142,811 $ (1,496 ) $ 44,292 $ 13,413 $ 199,020 Trex Commercial 1,927 (7 ) 672 618 3,210 Total $ 144,738 $ (1,503 ) $ 44,964 $ 14,031 $ 202,230 December 31, 2018 Trex Residential $ 131,823 $ (192 ) $ 41,421 $ 13,216 $ 186,268 Trex Commercial 2,749 — 868 3,251 6,868 Total $ 134,572 $ (192 ) $ 42,289 $ 16,467 $ 193,136

Seasonality

Seasonality	12 Months Ended
	Dec. 31, 2020
Text Block [Abstract]
Seasonality	17. SEASONALITY The operating results for Trex Residential 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 its products to a later period. As part of its normal business practice and consistent with industry practice, Trex Residential has historically offered incentive programs to its distributors and dealers to build inventory levels before the start of the prime deck-building season in order to ensure adequate availability of its product to meet anticipated seasonal consumer demand. The seasonal effects are often offset by the positive effect of the incentive programs. The operating results for Trex Commercial have not historically varied from quarter to quarter as a result of seasonality. However, they are driven by the timing of individual projects, which may vary significantly each period.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
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, 2020, the Company purchased reclaimed wood fiber requirements under purchase orders and long-term supply commitments not exceeding four years one The wood and polyethylene supply contracts generally provide that the Company is obligated to purchase all 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, 2020, the Company has purchase commitments under material supply contracts of $33.6 million and Product Warranty The Company warrants that its Trex 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 ® ® ® ® one 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 (collectively, elements). Estimates for these elements are quantified using 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 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 incoming claims received in the year ended December 31, 2020 was higher than the number of claims received in the year ended December 31, 2019 and exceeded the Company’s expectations for 2020. Prior to 2020, the number of incoming claims received declined each year since 2009. After evaluating the rise in incoming claims in its actuarial analysis, the Company increased its estimate of the number of future claims to be settled with payment. Average cost per claim experienced in the year ended December 31, 2020 was lower than that experienced in the year ended December 31, 2019, but slightly higher than the Company’s expectations for 2020. The Company estimates that average cost per claim will increase in future years, primarily due to inflation. As a result of the increase in estimated future claims and expected rise in future average cost per claim, in the three-month period ended September 30, 2020, the Company recorded a provision of $6.5 million to its warranty reserve for the future settlement of surface flaking claims. The Company believes its reserve at December 31, 2020 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 $2.1 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, 2020 Surface Other Total Beginning balance, January 1 $ 19,024 $ 6,470 $ 25,494 Provisions and changes in estimates 6,479 3,382 9,861 Settlements made during the period (4,178 ) (1,704 ) (5,882 ) Ending balance, December 31 $ 21,325 $ 8,148 $ 29,473 Year Ended December 31, 2019 Surface Other Total Beginning balance, January 1 $ 23,951 $ 6,803 $ 30,754 Provisions and changes in estimates — 979 979 Settlements made during the period (4,927 ) (1,312 ) (6,239 ) Ending balance, December 31 $ 19,024 $ 6,470 $ 25,494

Interim Financial Data (Unaudit

Interim Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Interim Financial Data (Unaudited)	19. INTERIM FINANCIAL DATA (Unaudited) Three Months Ended December 31, September 30, June 30, March 31, December 31, September 30, June 30, March 31, (In thousands, except share and per share data) Net sales $ 228,286 $ 231,502 $ 220,648 $ 200,395 $ 164,772 $ 194,551 $ 206,453 $ 179,571 Gross profit $ 92,392 $ 84,964 $ 92,405 $ 89,696 $ 71,263 $ 82,431 $ 83,444 $ 69,365 Net income $ 43,301 $ 42,710 $ 47,218 $ 42,402 $ 35,497 $ 41,976 $ 35,710 $ 31,555 Basic earnings per common share $ 0.37 $ 0.37 $ 0.41 $ 0.37 $ 0.31 $ 0.36 $ 0.31 $ 0.27 Basic weighted average common shares outstanding 115,791,757 115,773,030 115,733,934 116,259,058 116,591,434 116,800,120 116,972,384 117,086,956 Diluted earnings per common share $ 0.37 $ 0.37 $ 0.41 $ 0.37 $ 0.31 $ 0.36 $ 0.31 $ 0.27 Diluted weighted average common shares outstanding 116,169,754 116,134,623 116,061,988 116,647,442 117,025,466 117,209,206 117,375,080 117,658,354 The operating results for Trex Residential 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 its products to a later period. The operating results for Trex Commercial have not historically varied from quarter to quarter as a result of seasonality; however, they are driven by the timing of individual projects, which may vary significantly each period. On July 29, 2020, the Company’s Board of Directors approved a two-for-one

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts and Reserves	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, 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 Additions Deductions Balance Year ended December 31, 2020: Trex Residential product warranty reserve $ 25,494 $ 9,861 $ (5,882 ) $ 29,473 Income tax valuation allowance $ 2,988 $ 1 $ (214 ) $ 2,775 Year ended December 31, 2019: Trex Residential product warranty reserve $ 30,754 $ 979 $ (6,239 ) $ 25,494 Income tax valuation allowance $ 3,015 $ — $ (27 ) $ 2,988 Year ended December 31, 2018: Trex Residential product warranty reserve $ 34,999 $ 1,104 $ (5,349 ) $ 30,754 Income tax valuation allowance $ 3,096 $ — $ (81 ) $ 3,015

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Accounting	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 and its wholly-owned subsidiary, Trex Commercial Products, Inc. Intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates	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 and Cash Equivalents Cash equivalents consist of highly liquid investments purchased with original maturities of
Concentrations and Credit Risk	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, 2020, 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 recognized at the amount of revenue recognized on each shipment for Trex Residential products and for satisfied performance obligations for Trex Commercial products as the Company has an unconditional right to consideration from the customer and payment is due based solely on the passage of time. An estimate of expected credit losses is recognized as a valuation allowance and adjusted each reporting period. The estimate is based on the current expected credit loss model and is determined using an aging schedule, including past events, current conditions and reasonable and supportable forecasts about the future. There was no material valuation allowance recorded as of December 31, 2020 and December 31, 2019. In the years ended December 31, 2020, 2019, and 2018 sales to certain customers of Trex Residential accounted for 10% or more of the Company’s total net sales. For the year ended December 31, 2020, three customers represented approximately 56% of the Company’s total net sales. For the year ended December 31, 2019, For each year ended December 31, 2020, 2019, and 2018, approximately 28%, 27%, and 33%, respectively, of the Company’s materials purchases at Trex Residential were purchased from its
Inventories	Inventories Inventories for the Company’s composite decking and railing products are valued at the lower of cost (last-in, first-out, A majority of the Company’s products at Trex Residential 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 railing and staging products at Trex Commercial for the commercial and multi-family market are valued at the lower of cost (first-in, first-out Work-in
Property, Plant and Equipment	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. Unpaid liabilities related to property, plant and equipment are included in accounts payable and were $12.9 million and $0.8 million at December 31, 2020 and December 31, 2019, respectively. Cash flows for capital expenditures as reported in cash flows from investing activities in the Consolidated Statements of Cash Flows are adjusted to exclude unpaid amounts accrued at period end. 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
Leases	Leases The Company leases office space, storage warehouses and certain plant equipment under various operating leases. At inception of an arrangement, the Company evaluates, among other things, whether it has the right to control the use of an identified asset in order to determine if the arrangement is or contains a lease. Operating leases are included in operating lease right-of-use non-lease non-lease
Fair Value Measurement	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 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 The Company assigned its goodwill to reporting units and tests each reporting unit’s goodwill for impairment at least on an annual basis, or more frequently if an event occurs or circumstances change in the interim that indicate the carrying amount of reporting unit goodwill exceeds the implied fair value of that goodwill. 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 operating segment management, at a level below the Company’s chief operating decision maker, regularly reviews the operating results of the reporting unit. 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. In testing for goodwill impairment, the Company first assesses qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount, including goodwill. If the qualitative assessment indicates that the carrying amount of the reporting unit exceeds its fair value, including goodwill, the Company is then required to perform a quantitative goodwill impairment test. The quantitative goodwill impairment test, used to identify both the existence of impairment and the amount of impairment loss, compares the fair value of a reporting unit with its carrying amount, including goodwill. The fair value of a reporting unit refers to the price that would be received to sell the unit as a whole in an orderly transaction between market participants at the measurement date. If the carrying amount of a reporting unit exceeds its fair value, an impairment loss is recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. The Company measures fair value of the reporting units based on a present value of future cash flows (discounted cash flows model) 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, 2020, 2019, and 2018, the Company completed its annual impairment test of goodwill utilizing the qualitative assessment and concluded it was not more likely than
Product Warranty	Product Warranty The Company warrants that its Trex 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 ® ® ® ® 25 one available actual
Treasury Stock	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	Revenue Recognition Effective January 1, 2018, the Company retrospectively adopted the requirements of Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) 2014-09, Trex Residential Products. low-maintenance, eco-friendly Trex Commercial Products. Trex Commercial satisfies its performance obligation over time catch-up
Stock-Based Compensation	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	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. As of December 31, 2020, the Company has a valuation allowance of $2.8 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 Research and development costs are expensed as incurred. For the years ended December 31, 2020, 2019, and 2018, research and development costs were $3.4 million, $4.5 million, and $4.2 million, respectively, and have been included in “Selling, general and administrative expenses” in the accompanying Consolidated Statements of Comprehensive Income.
Advertising Costs	Advertising Costs The Company expenses its branding and advertising communication costs as incurred. Production costs are deferred and recognized as expense in the period that the related advertisement is first used. At December 31, 2020 and December 31, 2019 $0.01 million and $0.5 million was included in prepaid expenses for production costs, respectively. For the years ended December 31, 2020, 2019, and 2018, branding expenses, including advertising expenses as described above, were $31.7 million, $35.7 million, and $35.0 million, respectively.
Fair Value of Financial Instruments	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, and debt to approximate the fair value of the respective assets and liabilities on the Consolidated Balance Sheets at December 31, 2020 and 2019.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-15, Intangibles – Goodwill and Other – Internal-Use 350-40): internal-use In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses in Financial Instruments
New Accounting Standards Not Yet Adopted	New Accounting Standards Not Yet Adopted In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting reporting burdens as the market transitions from the London Interbank Offered Rate and other interbank offered rates to alternative reference rates. The new guidance allows entities to elect not to apply certain modification accounting requirements, if certain criteria are met, to contracts affected by what the guidance calls reference rate reform. An entity that makes this election would consider changes in reference rates and other contract modifications related to reference rate reform to be events that do not require contract remeasurement at the modification date or reassessment of a previous accounting determination. The ASU notes that changes in contract terms that are made to affect the reference rate reform transition are considered related to the replacement of a reference rate if they are not the result of a business decision that is separate from or in addition to changes to the terms of a contract to affect that transition. The guidance is effective upon issuance and generally can be applied as of March 12, 2020 through December 31, 2022. The Company does not expect adoption of the guidance to have a material effect on its consolidated financial statements. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes step-up

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Estimated Useful Lives of 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. Unpaid liabilities related to property, plant and equipment are included in accounts payable and were $12.9 million and $0.8 million at December 31, 2020 and December 31, 2019, respectively. Cash flows for capital expenditures as reported in cash flows from investing activities in the Consolidated Statements of Cash Flows are adjusted to exclude unpaid amounts accrued at period end. 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

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2020
Inventory Disclosure [Abstract]
Summary of Inventories	Inventories at LIFO value consist of the following as of December 31 (in thousands): 2020 2019 Finished goods $ 39,048 $ 42,281 Raw materials 44,475 31,686 Total FIFO inventories 83,523 73,967 Reserve to adjust inventories to LIFO value (16,821 ) (19,062 ) Total LIFO inventories $ 66,702 $ 54,905

Prepaid Expenses and Other As_2

Prepaid Expenses and Other Assets (Tables)	12 Months Ended
	Dec. 31, 2020
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): 2020 2019 Prepaid expenses $ 7,285 $ 8,282 Revenues in excess of billings 6,612 6,664 Contract retainage 2,267 1,832 Income tax receivable 7,823 2,675 Other 1,323 350 Total prepaid expenses and other assets $ 25,310 $ 19,803

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
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): 2020 2019 Machinery and equipment $ 312,870 $ 248,633 Building and improvements 61,860 51,547 Forklifts and tractors 16,003 10,870 Computer equipment 11,948 10,647 Furniture and fixtures 1,534 1,441 Construction in process 157,465 59,257 Land 11,351 11,417 Total property, plant and equipment 573,031 393,812 Accumulated depreciation (236,494 ) (222,512 ) Total property, plant and equipment, net $ 336,537 $ 171,300

Accrued Expenses and Other Li_2

Accrued Expenses and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
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): 2020 2019 Sales and marketing $ 22,938 $ 28,402 Compensation and benefits 21,156 13,475 Operating lease liabilities 6,708 7,079 Manufacturing costs 3,641 2,564 Customer deposits 1,174 2,905 Billings in excess of revenues 1,244 816 Other 5,470 3,024 Total accrued expenses $ 62,331 $ 58,265

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Debt	The Applicable Rate for Revolving B Commitments means the following percentages per annum, based upon the Consolidated Debt to Consolidated EBITDA Ratio as set forth in the most recent Compliance Certificate received by BOA as the Administrative Agent and as set forth in the New Credit Agreement: Pricing Tier Consolidated Debt to EBITDA Ratio Eurodollar Rate Base Rate Loans Revolving B 1 > 2.50:1.00 2.75 % 1.75 % 0.60 % 2 < 2.50:1.00 but > 2.00:1.00 2.50 % 1.50 % 0.55 % 3 < 2.00:1.00 but > 1.50:1.00 2.25 % 1.25 % 0.50 % 4 < 1.50:1.00 1.80 % 0.80 % 0.45 %

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Supplemental Cash Flow information and Supplemental balance sheet information related to operating leases to operating leases	The following table includes supplemental cash flow information for the years ended December 31, 2020 and December 31, 2019 and supplemental balance sheet information at December 31, 2020 and December 31, 2019 related to operating leases: For the Year Ended December 31 Supplemental Cash Flow Information 2020 2019 Cash paid for amounts included in the measurement of operating lease liabilities $ 8,736 $ 8,479 Operating ROU assets obtained in exchange for lease liabilities $ 1,427 $ 1,319 Supplemental Balance Sheet Information December 31, 2020 December 31, Operating lease ROU assets $ 34,382 $ 40,049 Operating lease liabilities: Accrued expenses and other current liabilities $ 6,708 $ 7,079 Operating lease liabilities 28,579 34,242 Total operating lease liabilities $ 35,287 $ 41,321
Maturities of operating lease liabilities	The following table summarizes maturities of operating lease liabilities at December 31, 2020 (in thousands): Maturities of operating lease liabilities 2021 $ 7,835 2022 7,345 2023 6,608 2024 6,265 2025 4,480 Thereafter 6,599 Total lease payments 39,132 Less imputed interest (3,845 ) Total operating liabilities $ 35,287

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 2018 Numerator: Net income $ 175,631 $ 144,738 $ 134,572 Denominator: Basic weighted average shares outstanding 115,888,859 116,861,194 117,479,340 Effect of dilutive securities: Stock appreciation rights 192,579 248,850 353,400 Restricted stock 171,428 205,454 301,864 Diluted weighted average shares outstanding 116,252,866 117,315,498 118,134,604 Basic earnings per share $ 1.52 $ 1.24 $ 1.15 Diluted earnings per share $ 1.51 $ 1.24 $ 1.14
Antidilutive Securities Excluded from Computation of Earnings Per Share	Year Ended December 31, 2020 2019 2018 Restricted stock — — 428 Stock appreciation rights 14,697 41,540 26,694

Revenue From Contracts With C_2

Revenue From Contracts With Customers (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Summary of Disaggregated Net Sales	The tables also include a reconciliation of the respective disaggregated net sales with the Company’s reportable segments (in thousands): Year Ended December 31, 2020 Reportable Segment Trex Trex Total Timing of Revenue Recognition and Type of Contract Products transferred at a point in time and variable consideration contracts $ 827,792 $ — $ 827,792 Products transferred over time and fixed price contracts — 53,039 53,039 $ 827,792 $ 53,039 $ 880,831 Year Ended December 31, 2019 Reportable Segment Trex Trex Total Timing of Revenue Recognition and Type of Contract Products transferred at a point in time and variable consideration contracts $ 694,267 $ — $ 694,267 Products transferred over time and fixed price contracts — 51,080 51,080 $ 694,267 $ 51,080 $ 745,347 Year Ended December 31, 2018 Reportable Segment Trex Trex Total Timing of Revenue Recognition and Type of Contract Products transferred at a point in time and variable consideration contracts $ 613,229 $ — $ 613,229 Products transferred over time and fixed price contracts — 71,021 71,021 $ 613,229 $ 71,021 $ 684,250

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Summary of Stock-Based Compensation Expense	The following table summarizes the Company’s stock-based compensation expense (in thousands): Year Ended December 31, 2020 2019 2018 Time-based restricted stock and restricted stock units $ 3,219 $ 3,676 $ 2,687 Performance-based restricted stock and restricted stock units 2,881 2,399 3,144 Stock appreciation rights 648 662 370 Employee stock purchase plan 383 193 143 Total stock-based compensation $ 7,131 $ 6,930 $ 6,344
Summary of Assumptions Used to Estimate Fair Value of Each SAR	For SARs issued in the years ended December 31, 2020, December 31, 2019 and December 31, 2018, respectively, the assumptions shown in the following table were used: Year Ended December 31, 2020 2019 2018 Dividend yield 0 % 0 % 0 % Average risk-free interest rate 1.3 % 2.5 % 2.7 % Expected term (years) 5 5 5 Expected volatility 38.3 % 39.1 % 40.5 %
SAR Activity	SAR activity under the Plan and all predecessor stock incentive plans is as follows: SARs Weighted-Average Weighted-Average Aggregate Outstanding at December 31, 2017 556,232 $ 6.73 Granted 42,520 $ 28.30 Exercised (121,800 ) $ 2.64 Canceled — $ — Outstanding at December 31, 2018 476,952 $ 9.63 Granted 49,072 $ 38.85 Exercised (217,528 ) $ 6.95 Canceled (4,458 ) $ 38.85 Outstanding at December 31, 2019 304,038 $ 15.79 Granted 43,830 $ 50.39 Exercised (54,592 ) $ 9.41 Canceled — $ — Outstanding at December 31, 2020 293,276 $ 22.15 5.4 $ 18,058,138 Vested at December 31, 2020 237,323 $ 17.05 4.7 $ 15,821,712 Exercisable at December 31, 2020 237,323 $ 17.05 4.7 $ 15,821,712
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 Weighted-Average Nonvested at December 31, 2017 306,236 $ 13.45 Granted 174,528 $ 27.36 Vested (169,100 ) $ 13.33 Forfeited (568 ) $ 17.53 Nonvested at December 31, 2018 311,096 $ 21.34 Granted 71,300 $ 38.12 Vested (162,650 ) $ 18.67 Forfeited (1,280 ) $ 31.17 Nonvested at December 31, 2019 218,466 $ 28.75 Granted 54,406 $ 53.97 Vested (111,036 ) $ 30.94 Forfeited (1,114 ) $ 40.34 Nonvested at December 31, 2020 160,722 $ 35.68
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 Weighted- Nonvested at December 31, 2017 233,316 $ 12.93 Granted 161,140 $ 17.63 Vested (212,044 ) $ 11.76 Forfeited — $ — Nonvested at December 31, 2018 182,412 $ 18.43 Granted 164,270 $ 23.82 Vested (222,004 ) $ 15.55 Forfeited (1,022 ) $ 29.23 Nonvested at December 31, 2019 123,656 $ 30.67 Granted 78,404 $ 39.60 Vested (128,762 ) $ 28.87 Forfeited (728 ) $ 41.12 Nonvested at December 31, 2020 72,570 $ 43.42

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Tax Provision (Benefit)	Income tax provision (benefit) consists of the following (in thousands): Year Ended December 31, 2020 2019 2018 Current income tax provision: Federal $ 35,423 $ 30,306 $ 33,578 State 10,455 6,952 7,674 45,878 37,258 41,252 Deferred income tax provision: Federal 12,603 6,928 988 State 522 778 49 13,125 7,706 1,037 Total income tax provision $ 59,003 $ 44,964 $ 42,289
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, 2020 2019 2018 U.S. Federal statutory taxes $ 49,273 $ 39,838 $ 37,141 State and local taxes, net of U.S. Federal benefit 10,641 8,412 7,716 Permanent items 1,198 1,266 470 Excess tax benefits from vesting or settlement of stock compensation awards (1,635 ) (3,540 ) (2,368 ) Federal credits (565 ) (654 ) (662 ) Other 91 (358 ) (8 ) Total income tax provision $ 59,003 $ 44,964 $ 42,289
Schedule of Deferred Tax Assets and Liabilities	Deferred tax assets and liabilities consist of the following (in thousands): As of December 31, 2020 2019 Deferred tax assets: Net operating losses $ 43 $ 88 Residential product warranty reserve 7,532 6,486 Stock-based compensation 1,071 1,055 Accruals not currently deductible and other 2,041 2,245 Inventories 5,548 5,780 Operating lease liability 9,081 10,618 State tax credit carryforwards 3,345 3,461 Gross deferred tax assets, before valuation allowance 28,661 29,733 Valuation allowance (2,775 ) (2,988 ) Gross deferred tax assets, after valuation allowance 25,886 26,745 Deferred tax liabilities: Depreciation (29,792 ) (17,267 ) Operating lease right-of-use (8,755 ) (10,162 ) Goodwill amortization (5,775 ) (4,782 ) Inventories and other (4,520 ) (4,365 ) Gross deferred tax liabilities (48,842 ) (36,576 ) Net deferred tax liability $ (22,956 ) $ (9,831 )

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Details of Segment Information	Segment Data (in thousands): Net Sales Net Income EBITDA Depreciation Income Tax Capital Total Assets December 31, 2020 Trex Residential $ 827,792 $ 171,197 $ 244,817 $ 17,131 $ 57,488 $ 171,784 $ 676,948 Trex Commercial 53,039 4,434 6,758 809 1,515 1,039 93,544 Total $ 880,831 $ 175,631 $ 251,575 $ 17,940 $ 59,003 $ 172,823 $ 770,492 December 31, 2019 Trex Residential $ 694,267 $ 142,811 $ 199,020 $ 13,413 $ 44,292 $ 65,399 $ 503,883 Trex Commercial 51,080 1,927 3,210 618 672 1,866 88,356 Total $ 745,347 $ 144,738 $ 202,230 $ 14,031 $ 44,964 $ 67,265 $ 592,239 December 31, 2018 Trex Residential $ 613,229 $ 131,823 $ 186,268 $ 13,216 $ 41,421 $ 31,392 $ 380,682 Trex Commercial 71,021 2,749 6,868 3,251 868 2,424 84,440 Total $ 684,250 $ 134,572 $ 193,136 $ 16,467 $ 42,289 $ 33,816 $ 465,122
Schedule of Reconciliation of Net Income to EBITDA	Reconciliation of Net Income (Loss) to EBITDA (in thousands): Net Income Interest Income Tax Depreciation EBITDA December 31, 2020 Trex Residential $ 171,197 $ (999 ) $ 57,488 $ 17,131 $ 244,817 Trex Commercial 4,434 — 1,515 809 6,758 Total $ 175,631 $ (999 ) $ 59,003 $ 17,940 $ 251,575 December 31, 2019 Trex Residential $ 142,811 $ (1,496 ) $ 44,292 $ 13,413 $ 199,020 Trex Commercial 1,927 (7 ) 672 618 3,210 Total $ 144,738 $ (1,503 ) $ 44,964 $ 14,031 $ 202,230 December 31, 2018 Trex Residential $ 131,823 $ (192 ) $ 41,421 $ 13,216 $ 186,268 Trex Commercial 2,749 — 868 3,251 6,868 Total $ 134,572 $ (192 ) $ 42,289 $ 16,467 $ 193,136

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 Surface Other Total Beginning balance, January 1 $ 19,024 $ 6,470 $ 25,494 Provisions and changes in estimates 6,479 3,382 9,861 Settlements made during the period (4,178 ) (1,704 ) (5,882 ) Ending balance, December 31 $ 21,325 $ 8,148 $ 29,473 Year Ended December 31, 2019 Surface Other Total Beginning balance, January 1 $ 23,951 $ 6,803 $ 30,754 Provisions and changes in estimates — 979 979 Settlements made during the period (4,927 ) (1,312 ) (6,239 ) Ending balance, December 31 $ 19,024 $ 6,470 $ 25,494

Interim Financial Data (Unaud_2

Interim Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Summary of Interim Financial Data	Three Months Ended December 31, September 30, June 30, March 31, December 31, September 30, June 30, March 31, (In thousands, except share and per share data) Net sales $ 228,286 $ 231,502 $ 220,648 $ 200,395 $ 164,772 $ 194,551 $ 206,453 $ 179,571 Gross profit $ 92,392 $ 84,964 $ 92,405 $ 89,696 $ 71,263 $ 82,431 $ 83,444 $ 69,365 Net income $ 43,301 $ 42,710 $ 47,218 $ 42,402 $ 35,497 $ 41,976 $ 35,710 $ 31,555 Basic earnings per common share $ 0.37 $ 0.37 $ 0.41 $ 0.37 $ 0.31 $ 0.36 $ 0.31 $ 0.27 Basic weighted average common shares outstanding 115,791,757 115,773,030 115,733,934 116,259,058 116,591,434 116,800,120 116,972,384 117,086,956 Diluted earnings per common share $ 0.37 $ 0.37 $ 0.41 $ 0.37 $ 0.31 $ 0.36 $ 0.31 $ 0.27 Diluted weighted average common shares outstanding 116,169,754 116,134,623 116,061,988 116,647,442 117,025,466 117,209,206 117,375,080 117,658,354

Business and Organization - Add

Business and Organization - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020Segment
Accounting Policies [Abstract]
Number of reportable segments	2

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)CustomerInstitutionSupplier	Dec. 31, 2019USD ($)Customer	Dec. 31, 2018USD ($)Customer
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	3	2
Number of customer accounted for 10% or more account receivable | Customer	2	3
Number of largest raw material suppliers | Supplier	4
Excess of the replacement cost of inventory over the LIFO value of inventory	$ (16,821)	$ (19,062)
Annual impairment test of goodwill	0	0	$ 0
Goodwill	68,500
Valuation allowance	2,775	2,988
Research and Development costs	3,400	4,500	4,200
Prepaid expenses for production costs of advertising	10	500
Branding Expenses	31,700	35,700	$ 35,000
Unpaid Liabilities relates to property plant and equipment	$ 12,900	$ 800
Operating leases with an initial term	12 months or less
Maximum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Operating Lease terms	8 years
Minimum [Member]
Schedule Of Significant Accounting Policies [Line Items]
Operating Lease terms	1 year
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	56.00%	57.00%	42.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Customer One [Member]
Schedule Of Significant Accounting Policies [Line Items]
Concentration risk as percentage of total	27.00%	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	15.00%	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	28.00%	27.00%	33.00%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Estimated Useful Lives of Property Plant and Equipment (Detail)	12 Months Ended
	Dec. 31, 2020
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
Maximum [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment estimated useful life	11 years
Minimum [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment estimated useful life	3 years

Inventories - Summary of Invent

Inventories - Summary of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Finished goods	$ 39,048	$ 42,281
Raw materials	44,475	31,686
Total FIFO inventories	83,523	73,967
Reserve to adjust inventories to LIFO value	(16,821)	(19,062)
Total LIFO inventories	$ 66,702	$ 54,905

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
LIFO inventory liquidations	$ 0	$ 0
Raw materials	$ 1,500,000	$ 1,200,000

Prepaid Expenses and Other As_3

Prepaid Expenses and Other Assets - Summary of Prepaid Expenses and Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Prepaid Expense and Other Assets [Abstract]
Prepaid expenses	$ 7,285	$ 8,282
Revenues in excess of billings	6,612	6,664
Contract retainage	2,267	1,832
Income tax receivable	7,823	2,675
Other	1,323	350
Total prepaid expenses and other assets	$ 25,310	$ 19,803

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets, Net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 68.5
Amortization of intangible asset	0.4	$ 0.4	$ 3.1
Intangible Assets	6.3	6.3
Accumulated Amortization	1.1	0.7
Commercial [Member]
Goodwill [Line Items]
Goodwill		$ 54.3
Residential [Member]
Goodwill [Line Items]
Goodwill	$ 14.2
Domain Names [Member]
Goodwill [Line Items]
Amortization period	15 years

Property, Plant and Equipment -

Property, Plant and Equipment - Summary of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 573,031	$ 393,812
Accumulated depreciation	(236,494)	(222,512)
Total property, plant and equipment, net	336,537	171,300
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	312,870	248,633
Building and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	61,860	51,547
Forklifts and Tractors [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	16,003	10,870
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	11,948	10,647
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,534	1,441
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	157,465	59,257
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 11,351	$ 11,417

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 573,031	$ 393,812
Depreciation expense	17,500	13,600	$ 13,400
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 157,465	$ 59,257

Accrued Expenses and Other Li_3

Accrued Expenses and Other Liabilities - Summary of Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Sales and marketing	$ 22,938	$ 28,402
Compensation and benefits	21,156	13,475
Operating lease liabilities	$ 6,708	7,079
Operating lease liability current statement of financial position [Extensible List]	us-gaap:OperatingLeaseLiabilityCurrent
Manufacturing costs	$ 3,641	2,564
Customer deposits	1,174	2,905
Billings in excess of revenues	1,244	816
Other	5,470	3,024
Total accrued expenses and other liabilities	$ 62,331	$ 58,265

Debt - Schedule Of Debt (Detail

Debt - Schedule Of Debt (Detail)	12 Months Ended
	Dec. 31, 2020
Pricing Tier One [Member]
Line of Credit Facility [Line Items]
Consolidated Debt to Consolidated EBITDA Ratio	> 2.50:1.00
Revolving B Commitment Fee	0.60%
Pricing Tier Two [Member]
Line of Credit Facility [Line Items]
Consolidated Debt to Consolidated EBITDA Ratio	< 2.50:1.00 but > 2.00:1.00
Revolving B Commitment Fee	0.55%
Pricing Tier Three [Member]
Line of Credit Facility [Line Items]
Consolidated Debt to Consolidated EBITDA Ratio	< 2.00:1.00 but > 1.50:1.00
Revolving B Commitment Fee	0.50%
Pricing Tier Four [Member]
Line of Credit Facility [Line Items]
Consolidated Debt to Consolidated EBITDA Ratio	< 1.50:1.00
Revolving B Commitment Fee	0.45%
London Interbank Offered Rate (LIBOR) [Member] | Pricing Tier One [Member]
Line of Credit Facility [Line Items]
Eurodollar Rate Loans / LIBOR Index	2.75%
London Interbank Offered Rate (LIBOR) [Member] | Pricing Tier Two [Member]
Line of Credit Facility [Line Items]
Eurodollar Rate Loans / LIBOR Index	2.50%
London Interbank Offered Rate (LIBOR) [Member] | Pricing Tier Three [Member]
Line of Credit Facility [Line Items]
Eurodollar Rate Loans / LIBOR Index	2.25%
London Interbank Offered Rate (LIBOR) [Member] | Pricing Tier Four [Member]
Line of Credit Facility [Line Items]
Eurodollar Rate Loans / LIBOR Index	1.80%
Base Rate [Member] | Pricing Tier One [Member]
Line of Credit Facility [Line Items]
Base Rate Loans	1.75%
Base Rate [Member] | Pricing Tier Two [Member]
Line of Credit Facility [Line Items]
Base Rate Loans	1.50%
Base Rate [Member] | Pricing Tier Three [Member]
Line of Credit Facility [Line Items]
Base Rate Loans	1.25%
Base Rate [Member] | Pricing Tier Four [Member]
Line of Credit Facility [Line Items]
Base Rate Loans	0.80%

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	May 26, 2020	Nov. 05, 2019	May 26, 2022	Dec. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Company indebtedness				$ 0	$ 0
Remaining available borrowing capacity				300,000,000
Federal Funds Rate [Member]
Line of Credit Facility [Line Items]
Interest rate	0.50%
Eurodollar Rate Loans [Member]
Line of Credit Facility [Line Items]
Interest rate	1.00%
Fourth Amended And Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Termination date of the Credit Agreement		Nov. 5, 2024
Revolver Loans Portion Effective January 1 through June 30 [Member] | Fourth Amended And Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount				250,000,000
Revolver Loans Portion Effective July 1 through December 31 [Member] | Fourth Amended And Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount				$ 200,000,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Additional Borrowing Capacity	$ 100,000,000		$ 100,000,000
Revolving Credit Facility [Member] | BOA [Member]
Line of Credit Facility [Line Items]
Lender Percentage	47.50%
Revolving Credit Facility [Member] | Well Fargo [Member]
Line of Credit Facility [Line Items]
Lender Percentage	28.00%
Revolving Credit Facility [Member] | Regions [Member]
Line of Credit Facility [Line Items]
Lender Percentage	24.50%

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Weighted average discount rate	3.47%	3.66%
Operating lease cost	$ 8.5	$ 8.4
Weighted average remaining lease term	5 years 7 months 6 days	6 years 6 months

Leases - Supplemental Cash flow

Leases - Supplemental Cash flow Information to operating leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Supplemental cash flow information
Cash paid for amounts included in the measurement of operating lease liabilities	$ 8,736	$ 8,479
Operating ROU assets obtained in exchange for lease liabilities	1,427	1,319
Supplemental balance sheet information
Operating lease ROU assets	34,382	40,049
Operating lease liabilities:
Accrued expenses and other current liabilities	6,708	7,079
Operating lease liabilities	28,579	34,242
Total operating lease liabilities	$ 35,287	$ 41,321

Leases - Maturities of Operatin

Leases - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Operating Lease Liabilities, Payments Due [Abstract]
2021	$ 7,835
2022	7,345
2023	6,608
2024	6,265
2025	4,480
Thereafter	6,599
Total lease payments	39,132
Less imputed interest	(3,845)
Total operating liabilities	$ 35,287	$ 41,321

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - $ / shares	Sep. 14, 2020	Dec. 31, 2020	Jul. 29, 2020	Apr. 29, 2020	Feb. 19, 2020	Dec. 31, 2019
Equity, Class of Treasury Stock [Line Items]
Common stock, par value		$ 0.01	$ 0.01
Common stock, shares authorized		180,000,000		180,000,000	120,000,000	180,000,000
Description of stock split	two-for-one stock split
Stock Repurchase Programs [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase program, authorized shares		11,600,000
Number of shares repurchased by the Company		2,800,000

Stockholders' Equity - Computat

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, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income	$ 43,301	$ 42,710	$ 47,218	$ 42,402	$ 35,497	$ 41,976	$ 35,710	$ 31,555	$ 175,631	$ 144,738	$ 134,572
Denominator:
Basic weighted average shares outstanding	115,791,757	115,773,030	115,733,934	116,259,058	116,591,434	116,800,120	116,972,384	117,086,956	115,888,859	116,861,194	117,479,340
Effect of dilutive securities:
Diluted weighted average shares outstanding	116,169,754	116,134,623	116,061,988	116,647,442	117,025,466	117,209,206	117,375,080	117,658,354	116,252,866	117,315,498	118,134,604
Basic earnings per share	$ 0.37	$ 0.37	$ 0.41	$ 0.37	$ 0.31	$ 0.36	$ 0.31	$ 0.27	$ 1.52	$ 1.24	$ 1.15
Diluted earnings per share	$ 0.37	$ 0.37	$ 0.41	$ 0.37	$ 0.31	$ 0.36	$ 0.31	$ 0.27	$ 1.51	$ 1.24	$ 1.14
Stock appreciation rights [Member]
Effect of dilutive securities:
Dilutive securities									192,579	248,850	353,400
Restricted stock [Member]
Effect of dilutive securities:
Dilutive securities									171,428	205,454	301,864

Stockholders' Equity - Antidilu

Stockholders' Equity - Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
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	0	0	428
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	14,697	41,540	26,694

Revenue From Contracts With C_3

Revenue From Contracts With Customers - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Revenue from Contract with Customer [Abstract]
Revenue remaining performance obligation	$ 65.8
Revenue remaining performance obligation description	greater than one year

Revenue From Contracts With C_4

Revenue From Contracts With Customers - Summary of Disaggregated Net Sales (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from contract with customers	$ 228,286	$ 231,502	$ 220,648	$ 200,395	$ 164,772	$ 194,551	$ 206,453	$ 179,571	$ 880,831	$ 745,347	$ 684,250
Products Transferred at a Point in Time and Variable Consideration Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									827,792	694,267	613,229
Products Transferred Over Time and Fixed Price Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									53,039	51,080	71,021
Residential [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									827,792	694,267	613,229
Residential [Member] | Products Transferred at a Point in Time and Variable Consideration Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									827,792	694,267	613,229
Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									53,039	51,080	71,021
Commercial [Member] | Products Transferred Over Time and Fixed Price Contracts [Member]
Disaggregation of Revenue [Line Items]
Revenue from contract with customers									$ 53,039	$ 51,080	$ 71,021

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Approximate number of shares employees purchased under the Employee Stock Purchase Plan	1,811,165
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	25,680,000
Number of common stock available for future issuance	11,253,930
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	2 years
Unrecognized compensation cost related to unvested awards	$ 1.7	$ 0.8	$ 1.6
Vesting period	3 years
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested awards	$ 0.6
Fair value assumptions method used	Black-Scholes option-pricing
Weighted-average fair value of grants	$ 17.81	$ 14.78	$ 11.05
Time-Based Restricted Stock and Time-Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested awards	$ 2.9
Total fair value of restricted shares vested	$ 6.1	$ 6	$ 5.1
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	2,400,000
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%
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%
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%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7,131	$ 6,930	$ 6,344
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	648	662	370
Time-Based Restricted Stock and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	3,219	3,676	2,687
Performance-Based Restricted Stock and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2,881	2,399	3,144
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 383	$ 193	$ 143

Stock-Based Compensation - Time

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Restricted Stock Activity [Line Items]
Nonvested, Shares, Beginning Balance	218,466	311,096	306,236
Time-based Restricted Stock, Granted	54,406	71,300	174,528
Time-based Restricted Stock, Vested	(111,036)	(162,650)	(169,100)
Time-based Restricted Stock, Forfeited	(1,114)	(1,280)	(568)
Nonvested, Shares, Ending Balance	160,722	218,466	311,096
Nonvested, Weighted-Average Grant Price Per Share, Beginning Balance	$ 28.75	$ 21.34	$ 13.45
Weighted-Average Grant Price Per Share, Granted	53.97	38.12	27.36
Weighted-Average Grant Price Per Share, Vested	30.94	18.67	13.33
Weighted-Average Grant Price Per Share, Forfeited	40.34	31.17	17.53
Nonvested, Weighted-Average Grant Price Per Share, Ending Balance	$ 35.68	$ 28.75	$ 21.34

Stock-Based Compensation - Perf

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Restricted Stock Activity [Line Items]
Nonvested, Shares, Beginning Balance	123,656	182,412	233,316
Performance-based Restricted Stock, Granted	78,404	164,270	161,140
Performance-based Restricted Stock, Vested	(128,762)	(222,004)	(212,044)
Performance-based Restricted Stock, Forfeited	(728)	(1,022)
Nonvested, Shares, Ending Balance	72,570	123,656	182,412
Nonvested, Weighted-Average Grant Price Per Share, Beginning Balance	$ 30.67	$ 18.43	$ 12.93
Weighted-Average Grant Price Per Share, Granted	39.60	23.82	17.63
Weighted-Average Grant Price Per Share, Vested	28.87	15.55	11.76
Weighted-Average Grant Price Per Share, Forfeited	41.12	29.23
Nonvested, Weighted-Average Grant Price Per Share, Ending Balance	$ 43.42	$ 30.67	$ 18.43

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Assumptions Used to Estimate Fair Value of Each SAR (Detail) - Stock Appreciation Rights [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement by Share Based Payment Award Fair Value Assumptions and Methodology [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Average risk-free interest rate	1.30%	2.50%	2.70%
Expected term (years)	5 years	5 years	5 years
Expected volatility	38.30%	39.10%	40.50%

Stock-Based Compensation - SAR

Stock-Based Compensation - SAR Activity (Detail) - Stock Appreciation Rights [Member] - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Stock Appreciation Rights Activity [Line Items]
SARs Outstanding, Beginning Balance	304,038	476,952	556,232
Granted, SARs	43,830	49,072	42,520
Exercised, SARs	(54,592)	(217,528)	(121,800)
Canceled, SARs		(4,458)
Shares Outstanding, SARs, Ending Balance	293,276	304,038	476,952
Outstanding, Weighted Average Grant Price Per Share, Beginning Balance	$ 15.79	$ 9.63	$ 6.73
Vested, SARs	237,323
Granted, Weighted Average Grant Price Per Share	$ 50.39	38.85	28.30
Exercisable, SARs	237,323
Exercised, Weighted Average Grant Price Per Share	$ 9.41	6.95	2.64
Canceled, Weighted Average Grant Price Per Share		38.85
Outstanding, Weighted Average Grant Price Per Share, Ending Balance	22.15	$ 15.79	$ 9.63
Vested, Weighted Average Grant Price Per Share	17.05
Exercisable, Weighted Average Grant Price Per Share	$ 17.05
Weighted Average Remaining Contractual Life, Outstanding	5 years 4 months 24 days
Weighted Average Remaining Contractual Life, Vested	4 years 8 months 12 days
Weighted Average Remaining Contractual Life, Exercisable	4 years 8 months 12 days
Aggregate Intrinsic Value, Outstanding	$ 18,058,138
Aggregate Intrinsic Value, Vested	15,821,712
Aggregate Intrinsic Value, Exercisable	$ 15,821,712

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Employer's contribution	$ 5.7	$ 4.6	$ 4.2

Income Taxes - Income Tax Provi

Income Taxes - Income Tax Provision (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current income tax provision:
Federal	$ 35,423	$ 30,306	$ 33,578
State	10,455	6,952	7,674
Total	45,878	37,258	41,252
Deferred income tax provision:
Federal	12,603	6,928	988
State	522	778	49
Total	13,125	7,706	1,037
Total income tax provision	$ 59,003	$ 44,964	$ 42,289

Income Taxes - Reconciliation o

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, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
U.S. Federal statutory taxes	$ 49,273	$ 39,838	$ 37,141
State and local taxes, net of U.S. Federal benefit	10,641	8,412	7,716
Permanent items	1,198	1,266	470
Excess tax benefits from vesting or settlement of stock compensation awards	(1,635)	(3,540)	(2,368)
Federal credits	(565)	(654)	(662)
Other	91	(358)	(8)
Total income tax provision	$ 59,003	$ 44,964	$ 42,289

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating losses	$ 43	$ 88
Residential product warranty reserve	7,532	6,486
Stock-based compensation	1,071	1,055
Accruals not currently deductible and other	2,041	2,245
Inventories	5,548	5,780
Operating lease liability	9,081	10,618
State tax credit carryforwards	3,345	3,461
Gross deferred tax assets, before valuation allowance	28,661	29,733
Valuation allowance	(2,775)	(2,988)
Gross deferred tax assets, after valuation allowance	25,886	26,745
Deferred tax liabilities:
Depreciation	(29,792)	(17,267)
Operating lease right-of-use asset	(8,755)	(10,162)
Goodwill amortization	(5,775)	(4,782)
Inventories and other	(4,520)	(4,365)
Gross deferred tax liabilities	(48,842)	(36,576)
Net deferred tax liability	$ (22,956)	$ (9,831)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020USD ($)Tax_Positions	Dec. 31, 2019USD ($)
Income Tax Contingency [Line Items]
Valuation allowance	$ 2,775,000	$ 2,988,000
Unrecognized tax benefits number of tax matters | Tax_Positions	0
Unrecognized tax benefits related to identified uncertain tax positions	$ 0
Tax years subject to examination	2016 2017 2018

Segment Information - Additiona

Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020RetailerSegment
Segment Reporting Information [Line Items]
Number of reportable segment | Segment	2
Number of national retailers | Retailer	2

Segment Information - Details o

Segment Information - Details of Segment Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net Sales	$ 228,286	$ 231,502	$ 220,648	$ 200,395	$ 164,772	$ 194,551	$ 206,453	$ 179,571	$ 880,831	$ 745,347	$ 684,250
Net Income	43,301	$ 42,710	$ 47,218	$ 42,402	35,497	$ 41,976	$ 35,710	$ 31,555	175,631	144,738	134,572
Depreciation and amortization									17,939	14,031	16,597
Income Tax Expense									59,003	44,964	42,289
Total Assets	770,492				592,239				770,492	592,239
Residential [Member]
Segment Reporting Information [Line Items]
Net Sales									827,792	694,267	613,229
Commercial [Member]
Segment Reporting Information [Line Items]
Net Sales									53,039	51,080	71,021
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Sales									880,831	745,347	684,250
Net Income									175,631	144,738	134,572
EBITDA									251,575	202,230	193,136
Depreciation and amortization									17,940	14,031	16,467
Income Tax Expense									59,003	44,964	42,289
Capital Expenditures									172,823	67,265	33,816
Total Assets	770,492				592,239				770,492	592,239	465,122
Operating Segments [Member] | Residential [Member]
Segment Reporting Information [Line Items]
Net Sales									827,792	694,267	613,229
Net Income									171,197	142,811	131,823
EBITDA									244,817	199,020	186,268
Depreciation and amortization									17,131	13,413	13,216
Income Tax Expense									57,488	44,292	41,421
Capital Expenditures									171,784	65,399	31,392
Total Assets	676,948				503,883				676,948	503,883	380,682
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net Sales									53,039	51,080	71,021
Net Income									4,434	1,927	2,749
EBITDA									6,758	3,210	6,868
Depreciation and amortization									809	618	3,251
Income Tax Expense									1,515	672	868
Capital Expenditures									1,039	1,866	2,424
Total Assets	$ 93,544				$ 88,356				$ 93,544	$ 88,356	$ 84,440

Segment Information - Schedule

Segment Information - Schedule of Reconciliation of Net Income to EBITDA (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net Income	$ 43,301	$ 42,710	$ 47,218	$ 42,402	$ 35,497	$ 41,976	$ 35,710	$ 31,555	$ 175,631	$ 144,738	$ 134,572
Interest (income) expense, net									(999)	(1,503)	(192)
Income Tax Expense									59,003	44,964	42,289
Depreciation and Amortization									17,939	14,031	16,597
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Income									175,631	144,738	134,572
Interest (income) expense, net									(999)	(1,503)	(192)
Income Tax Expense									59,003	44,964	42,289
Depreciation and Amortization									17,940	14,031	16,467
EBITDA									251,575	202,230	193,136
Operating Segments [Member] | Residential [Member]
Segment Reporting Information [Line Items]
Net Income									171,197	142,811	131,823
Interest (income) expense, net									(999)	(1,496)	(192)
Income Tax Expense									57,488	44,292	41,421
Depreciation and Amortization									17,131	13,413	13,216
EBITDA									244,817	199,020	186,268
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net Income									4,434	1,927	2,749
Interest (income) expense, net									0	(7)	0
Income Tax Expense									1,515	672	868
Depreciation and Amortization									809	618	3,251
EBITDA									$ 6,758	$ 3,210	$ 6,868

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Schedule Of Commitments And Contingencies [Line Items]
Change in warranty reserve for disclosure purposes only	$ 2,100
Surface Flaking [Member]
Schedule Of Commitments And Contingencies [Line Items]
Provisions and changes in estimates for the future settlement of surface flaking claims	$ 6,500
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%
Provisions and changes in estimates for the future settlement of surface flaking claims	$ 9,861	$ 979
Surface Flaking Warranty Reserve [Member] | Surface Flaking [Member]
Schedule Of Commitments And Contingencies [Line Items]
Provisions and changes in estimates for the future settlement of surface flaking claims	$ 6,479	$ 0
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
Commercial Railing And Staging Systems [Member] | Commercial Use [Member] | Minimum [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	1 year
Commercial Railing And Staging Systems [Member] | Commercial Use [Member] | Maximum [Member]
Schedule Of Commitments And Contingencies [Line Items]
Warranty period	3 years
Raw Material Supply Contracts [Member]
Schedule Of Commitments And Contingencies [Line Items]
Purchase commitment	$ 33,600
Purchase commitment, due in second year	15,000
Purchase commitment, due in third year	22,700
Purchase commitment, due in fourth year	$ 22,700

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Reconciliation of Company's Residential Product Warranty Reserve (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Surface Flaking Warranty Reserve [Member]
Product Warranty Liability [Line Items]
Beginning balance	$ 25,494	$ 30,754
Provisions and changes in estimates	9,861	979
Settlements made during the period	(5,882)	(6,239)
Ending balance	29,473	25,494
Surface Flaking [Member]
Product Warranty Liability [Line Items]
Provisions and changes in estimates	6,500
Surface Flaking [Member] | Surface Flaking Warranty Reserve [Member]
Product Warranty Liability [Line Items]
Beginning balance	19,024	23,951
Provisions and changes in estimates	6,479	0
Settlements made during the period	(4,178)	(4,927)
Ending balance	21,325	19,024
Other Residential [Member] | Surface Flaking Warranty Reserve [Member]
Product Warranty Liability [Line Items]
Beginning balance	6,470	6,803
Provisions and changes in estimates	3,382	979
Settlements made during the period	(1,704)	(1,312)
Ending balance	$ 8,148	$ 6,470

Interim Financial Data (Unaud_3

Interim Financial Data (Unaudited) - Summary of Interim Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Data [Abstract]
Net sales	$ 228,286	$ 231,502	$ 220,648	$ 200,395	$ 164,772	$ 194,551	$ 206,453	$ 179,571	$ 880,831	$ 745,347	$ 684,250
Gross profit	92,392	84,964	92,405	89,696	71,263	82,431	83,444	69,365	359,457	306,503	294,894
Net income	$ 43,301	$ 42,710	$ 47,218	$ 42,402	$ 35,497	$ 41,976	$ 35,710	$ 31,555	$ 175,631	$ 144,738	$ 134,572
Basic earnings per common share	$ 0.37	$ 0.37	$ 0.41	$ 0.37	$ 0.31	$ 0.36	$ 0.31	$ 0.27	$ 1.52	$ 1.24	$ 1.15
Basic weighted average common shares outstanding	115,791,757	115,773,030	115,733,934	116,259,058	116,591,434	116,800,120	116,972,384	117,086,956	115,888,859	116,861,194	117,479,340
Diluted earnings per common share	$ 0.37	$ 0.37	$ 0.41	$ 0.37	$ 0.31	$ 0.36	$ 0.31	$ 0.27	$ 1.51	$ 1.24	$ 1.14
Diluted weighted average common shares outstanding	116,169,754	116,134,623	116,061,988	116,647,442	117,025,466	117,209,206	117,375,080	117,658,354	116,252,866	117,315,498	118,134,604

Interim Financial Data (Unaud_4

Interim Financial Data (Unaudited) - Additional Information (Detail)	Jul. 29, 2020
Quarterly Financial Data [Abstract]
Stock split	2

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts and Reserves (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Warranty Reserve [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 25,494	$ 30,754	$ 34,999
Additions (Reductions) Charged to Cost and Expenses	9,861	979	1,104
Deductions	(5,882)	(6,239)	(5,349)
Balance at End of Period	29,473	25,494	30,754
Valuation Allowance of Deferred Tax Assets [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	2,988	3,015	3,096
Additions (Reductions) Charged to Cost and Expenses	1
Deductions	(214)	(27)	(81)
Balance at End of Period	$ 2,775	$ 2,988	$ 3,015