Stock-Based Compensation (Policies)	6 Months Ended
	Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation	The Company has one stock-based compensation plan, the 2014 Stock Incentive Plan (Plan), approved by the Company’s stockholders in April 2014. The Plan amended and restated in its entirety the Trex Company, Inc. 2005 Stock Incentive Plan. The Plan was subsequently amended and restated by the Company’s Board of Directors in May 2014 and May 2018. 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 12,840,000 and as of June 30, 2019, the total number of shares available for future issuance are 5,761,081.