Quarterly report pursuant to Section 13 or 15(d)

Acquisitions - Unaudited Supplemental Proforma Results of Operations (Detail)

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Acquisitions - Unaudited Supplemental Proforma Results of Operations (Detail) (USD $)
In Thousands, except Per Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Business Combinations [Abstract]    
Revenues $ 1,893,115us-gaap_BusinessAcquisitionsProFormaRevenue $ 1,951,362us-gaap_BusinessAcquisitionsProFormaRevenue
Gross profit 253,737pwr_BusinessAcquisitionsProFormaGrossProfit 288,846pwr_BusinessAcquisitionsProFormaGrossProfit
Selling, general and administrative expenses 150,732pwr_BusinessAcquisitionsProFormaSellingGeneralAndAdministrativeExpenses 183,265pwr_BusinessAcquisitionsProFormaSellingGeneralAndAdministrativeExpenses
Amortization of intangible assets 8,906pwr_BusinessAcquisitionsProFormaAmortizationOfIntangibleAssets 11,486pwr_BusinessAcquisitionsProFormaAmortizationOfIntangibleAssets
Net income 58,132us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss 60,482us-gaap_BusinessAcquisitionsProFormaNetIncomeLoss
Net income attributable to common stock $ 53,431pwr_BusinessAcquisitionsProFormaNetIncomeLossAttributableToCommonStock $ 56,242pwr_BusinessAcquisitionsProFormaNetIncomeLossAttributableToCommonStock
Earnings per share attributable to common stock - basic and diluted $ 0.25us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted $ 0.25us-gaap_BusinessAcquisitionProFormaEarningsPerShareDiluted