Annual report pursuant to Section 13 and 15(d)

Acquisitions - Additional Information (Detail)

v3.3.1.900
Acquisitions - Additional Information (Detail)
$ in Thousands
12 Months Ended
Dec. 31, 2015
USD ($)
Entity
shares
Dec. 31, 2014
USD ($)
Entity
shares
Dec. 31, 2013
USD ($)
Entity
shares
Business Acquisition [Line Items]      
Aggregate consideration for acquisitions $ 110,428 $ 279,533 $ 341,100
Value of Quanta common stock and exchangeable shares issued 10,127 $ 134,500 $ 88,900
Contingent consideration $ 1,001    
Number of business acquisitions | Entity 11 9 6
Goodwill acquired $ 51,860 $ 174,485  
Fair value of accounts receivable acquired 20,600 117,200  
Goodwill expected to be deductible for income tax 33,900 43,500  
Income (loss) from continuing operations before income taxes 228,675 426,599 $ 588,320
2015 Acquisitions [Member]      
Business Acquisition [Line Items]      
Net tangible assets acquired 44,700    
Goodwill acquired 51,860    
Other intangible assets, acquired 25,000    
Revenues 104,600 314,100 251,300
Income (loss) from continuing operations before income taxes 300 3,400 $ 18,200
Acquisition costs $ 3,600 $ 11,600  
Common Stock [Member]      
Business Acquisition [Line Items]      
Number of shares granted for acquired companies | shares 461,037 686,382 3,547,482
Canadian Subsidiaries [Member] | Exchangeable Shares [Member]      
Business Acquisition [Line Items]      
Number of shares granted for acquired companies | shares   3,825,971  
Series G Preferred Stock [Member]      
Business Acquisition [Line Items]      
Number of shares granted for acquired companies | shares   1  
Series G Preferred Stock [Member] | Canadian Subsidiaries [Member] | Exchangeable Shares [Member]      
Business Acquisition [Line Items]      
Number of shares granted for acquired companies | shares   899,858  
Electric Power Infrastructure Services Business [Member]      
Business Acquisition [Line Items]      
Number of business acquisitions | Entity 8    
Electric Power Infrastructure Services Business [Member] | United States [Member]      
Business Acquisition [Line Items]      
Number of business acquisitions | Entity 4 1  
Electric Power Infrastructure Services Business [Member] | Australia [Member]      
Business Acquisition [Line Items]      
Number of business acquisitions | Entity 1 1  
Electric Power Infrastructure Services Business [Member] | Canada [Member]      
Business Acquisition [Line Items]      
Number of business acquisitions | Entity 3 4  
Oil and Gas Infrastructure Services Business [Member]      
Business Acquisition [Line Items]      
Number of business acquisitions | Entity 3    
Oil and Gas Infrastructure Services Business [Member] | United States [Member]      
Business Acquisition [Line Items]      
Number of business acquisitions | Entity 1 1  
Oil and Gas Infrastructure Services Business [Member] | Australia [Member]      
Business Acquisition [Line Items]      
Number of business acquisitions | Entity 1    
Oil and Gas Infrastructure Services Business [Member] | Canada [Member]      
Business Acquisition [Line Items]      
Number of business acquisitions | Entity 1 2  
Electric Power Division [Member]      
Business Acquisition [Line Items]      
Goodwill acquired $ 31,224 $ 71,517 $ 112,500
Oil and Gas Infrastructure Division [Member]      
Business Acquisition [Line Items]      
Goodwill acquired $ 20,636 $ 102,968 $ 143,300