Acquisitions - 2015 Acquisitions (Detail) $ in Millions |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2015
USD ($)
Acquisition
shares
|
Dec. 31, 2017
USD ($)
|
Dec. 31, 2016
USD ($)
|
|
Business Acquisition [Line Items] | |||
Contingent consideration | $ 1.0 | $ 51.1 | $ 18.7 |
Acquisitions 2015 | |||
Business Acquisition [Line Items] | |||
Number of business acquisitions | Acquisition | 11 | ||
Cash paid or payable | $ 110.6 | ||
Number of shares granted for acquired companies (in shares) | shares | 461,037 | ||
Value of Quanta common stock issued | $ 10.1 | ||
Contingent consideration | $ 1.0 | ||
Acquisitions 2015 | Electric Power Infrastructure Services Business | |||
Business Acquisition [Line Items] | |||
Number of business acquisitions | Acquisition | 8 | ||
Acquisitions 2015 | Oil and Gas Infrastructure Services Business | |||
Business Acquisition [Line Items] | |||
Number of business acquisitions | Acquisition | 3 |