| Document and Entity Information | Sep. 07, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 07, 2023 |
| Entity Registrant Name | TREX COMPANY, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-14649 |
| Entity Tax Identification Number | 54-1910453 |
| Entity Address, Address Line One | 2500 Trex Way |
| Entity Address, City or Town | Winchester |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 22601 |
| City Area Code | 540 |
| Local Phone Number | 542-6300 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001069878 |
| Title of 12(b) Security | Common stock |
| Trading Symbol | TREX |
| Security Exchange Name | NYSE |
