Quarterly report pursuant to Section 13 or 15(d)

Debt Obligations - Information on Borrowings under Current and Prior Credit Facility and Applicable Interest Rates (Detail)

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Debt Obligations - Information on Borrowings under Current and Prior Credit Facility and Applicable Interest Rates (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Line of Credit Facility [Abstract]  
Maximum amount outstanding during the period $ 123,768us-gaap_LineOfCreditFacilityMaximumAmountOutstandingDuringPeriod
Average daily amount outstanding under the credit facility $ 92,351us-gaap_LineOfCreditFacilityAverageOutstandingAmount
Weighted-average interest rate 2.24%pwr_LongTermDebtWeightedAverageInterestRateDuringPeriod