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Employee Benefit Plans - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Employee Benefit Plans [Line Items]      
Multiemployer defined contribution and other benefit plan contributions other than MEP DBP $ 147,100,000 $ 129,000,000 $ 104,400,000
Contributions to the deferred compensation plan 1,000,000 300,000 0
Deferred compensation obligations included in other long-term liabilities 11,700,000 2,300,000  
Deferred compensation obligations included in other long-term assets $ 11,300,000 2,000,000  
401K Plan [Member]      
Employee Benefit Plans [Line Items]      
Percentage of contribution by employer of each employee's contribution up to 3% 100.00%    
Percentage of contribution by employer of each employee who contributes between three and six percent 50.00%    
Percentage of employee contribution, lower range 3.00%    
Percentage of employee contribution, high range 6.00%    
Contributions to Quanta 401(k) Plan $ 17,700,000 $ 13,900,000 $ 11,500,000
Red Zone [Member]      
Employee Benefit Plans [Line Items]      
Percentage Funded in this Zone Less than 65%    
Yellow Zone [Member]      
Employee Benefit Plans [Line Items]      
Percentage Funded in this Zone Less than 80%    
Green Zone [Member]      
Employee Benefit Plans [Line Items]      
Percentage Funded in this Zone at least 80%