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Commitments and Contingencies - Concentrations of Credit Risk (Detail) - Electric Power Infrastructure Services Segment Customer One - Net Receivable Position - Customer Concentration Risk - Quanta's Electric Power Infrastructure Services Segment
12 Months Ended
Dec. 31, 2016
Customer
Concentration Risk [Line Items]  
Number of customers representing ten percent or more of concentration risk 1
Concentration risk percentage 16.00%