Quarterly report pursuant to Section 13 or 15(d)

Equity-Based Compensation - Additional Information (Detail)

v2.4.1.9
Equity-Based Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
2007 Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Aggregate number of shares of common stock that may be issued 4,000,000pwr_CommonStockAvailableForAwardsPursuantToPlan
/ us-gaap_StatementEquityComponentsAxis
= pwr_TwoThousandAndSevenPlanMember
   
2011 Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Aggregate number of shares of common stock that may be issued 11,750,000pwr_CommonStockAvailableForAwardsPursuantToPlan
/ us-gaap_StatementEquityComponentsAxis
= pwr_TwoThousandAndElevenPlanMember
   
Restricted Stock Units to be Settled in Cash [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of common stock shares that may be received by RSU holder 1pwr_NumberOfCommonStockSharesReceivedByRsuHolder
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockUnitsToBeSettledInCashMember
   
Compensation expense related to Restricted Stock Units to be settled in cash $ 1.3us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockUnitsToBeSettledInCashMember
$ 0.7us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockUnitsToBeSettledInCashMember
 
Payment to settle liabilities under compensation plan 0.9us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockUnitsToBeSettledInCashMember
2.1us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockUnitsToBeSettledInCashMember
 
Accrued liabilities under Compensation Plan 3.3us-gaap_DeferredCompensationShareBasedArrangementsLiabilityCurrent
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockUnitsToBeSettledInCashMember
  2.9us-gaap_DeferredCompensationShareBasedArrangementsLiabilityCurrent
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockUnitsToBeSettledInCashMember
Restricted Stock Units to be Settled in Cash [Member] | Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period for restricted stock and restricted stock units 3 years    
Restricted Stock Units to be Settled in Cash [Member] | Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period for restricted stock and restricted stock units 2 years    
Restricted Stock and Restricted Stock Units to be Settled in Common Stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted, shares 1,200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
1,300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
 
Granted, weighted average grant date fair value, per share $ 27.77us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
$ 35.19us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
 
Awards vested 1,200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
1,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
 
Fair value of restricted stock, vested 33.2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
33.5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
 
Unrecognized compensation cost, related to unvested restricted stock, total 53.4us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
   
Expected weighted average period to recognize compensation cost on restricted stock and RSUs to be settled in stock (in years) 2 years 29 days    
Restricted Stock and Restricted Stock Units to be Settled in Common Stock [Member] | Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period for restricted stock and restricted stock units 3 years    
Restricted Stock and Restricted Stock Units to be Settled in Common Stock [Member] | Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period for restricted stock and restricted stock units 2 years    
Performance Units [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted, shares 200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Granted, weighted average grant date fair value, per share $ 28.16us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Awards vested 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Required performance period 3 years    
Performance units vesting conditions These performance units cliff-vest at the end of a three-year performance period based on achievement of three-year company financial performance targets and strategic initiatives established by the Compensation Committee.    
Compensation costs $ 0.7us-gaap_EmployeeBenefitsAndShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Number of common shares issued in connection with performance units 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Performance Units [Member] | Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Performance units performance percentage 200.00%pwr_PerformanceBasedAwardPerformancePercentage
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
   
Performance Units [Member] | Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Performance units performance percentage 0.00%pwr_PerformanceBasedAwardPerformancePercentage
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember