Quarterly report pursuant to Section 13 or 15(d)

Acquisitions - Additional Information (Detail)

v3.7.0.1
Acquisitions - Additional Information (Detail) - Acquisitions 2016 [Member]
$ in Thousands
 12 Months Ended
Mar. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Acquisition
shares
Business Acquisition [Line Items]    
Number of business acquisitions | Acquisition   5
Cash paid or payable   $ 75,941
Contingent consideration   $ 18,683
Number of shares granted for acquired companies | shares   70,840
Value of Quanta common stock and exchangeable shares issued   $ 1,508
Net tangible assets acquired $ 17,000  
Goodwill acquired 18,400 44,527
Other intangible assets acquired $ 3,100 11,467
Fair value of accounts receivable acquired   14,400
Goodwill expected to be deductible for income tax   2,000
Maximum [Member]    
Business Acquisition [Line Items]    
Contingent consideration   $ 39,500
Electric Power Infrastructure Services Business [Member]    
Business Acquisition [Line Items]    
Number of business acquisitions | Acquisition   4
Electric Power Infrastructure Services Business [Member] | Australia [Member]    
Business Acquisition [Line Items]    
Number of business acquisitions | Acquisition   1
Electric Power Infrastructure Services Business [Member] | United States [Member]    
Business Acquisition [Line Items]    
Number of business acquisitions | Acquisition   1
Electric Power Infrastructure Services Business [Member] | Canada [Member]    
Business Acquisition [Line Items]    
Number of business acquisitions | Acquisition   2
Oil and Gas Infrastructure Services Business [Member] | United States [Member]    
Business Acquisition [Line Items]    
Number of business acquisitions | Acquisition   1
Electric Power Division [Member]    
Business Acquisition [Line Items]    
Goodwill acquired   $ 24,200
Oil and Gas Infrastructure Division [Member]    
Business Acquisition [Line Items]    
Goodwill acquired   $ 20,300