| Document and Entity Information | Oct. 07, 2019 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001050915 |
| Document Type | 8-K |
| Document Period End Date | Oct. 7, 2019 |
| Entity Registrant Name | Quanta Services, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-13831 |
| Entity Tax Identification Number | 74-2851603 |
| Entity Address, Address Line One | 2800 Post Oak Boulevard |
| Entity Address, Address Line Two | Suite 2600 |
| Entity Address, City or Town | Houston |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 77056 |
| City Area Code | (713) |
| Local Phone Number | 629-7600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.00001 |
| Trading Symbol | PWR |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
