| Document and Entity Information | Oct. 24, 2024 |
| Document and Entity Information | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 24, 2024 |
| Securities Act File Number | 1-13011 |
| Entity Registrant Name | Comfort Systems USA, Inc. |
| Entity Central Index Key | 0001035983 |
| Entity Tax Identification Number | 76-0526487 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 675 Bering Drive, Suite 400 |
| Entity Address, State or Province | TX |
| Entity Address, City or Town | Houston |
| Entity Address, Postal Zip Code | 77057 |
| City Area Code | 713 |
| Local Phone Number | 830-9600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 par value |
| Trading Symbol | FIX |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
