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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
 3 Months Ended 12 Months Ended 0 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Dec. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 06, 2013
Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]                
Cash and cash equivalents $ 190,515,000us-gaap_CashAndCashEquivalentsAtCarryingValue   $ 488,777,000us-gaap_CashAndCashEquivalentsAtCarryingValue $ 190,515,000us-gaap_CashAndCashEquivalentsAtCarryingValue $ 488,777,000us-gaap_CashAndCashEquivalentsAtCarryingValue $ 394,701,000us-gaap_CashAndCashEquivalentsAtCarryingValue   $ 315,349,000us-gaap_CashAndCashEquivalentsAtCarryingValue
Cash equivalents 107,600,000us-gaap_CashEquivalentsAtCarryingValue   247,800,000us-gaap_CashEquivalentsAtCarryingValue 107,600,000us-gaap_CashEquivalentsAtCarryingValue 247,800,000us-gaap_CashEquivalentsAtCarryingValue      
Number of days after accounts receivable are treated as delinquent       30 days 30 days      
Number of days related to outstanding accounts receivable for analysis of the allowance for doubtful accounts       At least 90 days        
Allowances for doubtful accounts on current receivable 6,174,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent   5,215,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent 6,174,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent 5,215,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent      
Revenue associated with change order           165,000,000pwr_RevenueAssociatedWithChangeOrder    
Provision for long-term contract receivable 49,900,000pwr_ProvisionForLongtermContractReceivable 52,500,000pwr_ProvisionForLongtermContractReceivable   102,460,000pwr_ProvisionForLongtermContractReceivable        
Current retainage balances 307,300,000us-gaap_ContractReceivableRetainageDueOneYearOrLess   194,500,000us-gaap_ContractReceivableRetainageDueOneYearOrLess 307,300,000us-gaap_ContractReceivableRetainageDueOneYearOrLess 194,500,000us-gaap_ContractReceivableRetainageDueOneYearOrLess      
Non-current retainage balances 19,600,000us-gaap_ContractReceivableRetainageDueAfterOneYear   50,800,000us-gaap_ContractReceivableRetainageDueAfterOneYear 19,600,000us-gaap_ContractReceivableRetainageDueAfterOneYear 50,800,000us-gaap_ContractReceivableRetainageDueAfterOneYear      
Unbilled receivables 165,500,000us-gaap_UnbilledContractsReceivable   179,200,000us-gaap_UnbilledContractsReceivable 165,500,000us-gaap_UnbilledContractsReceivable 179,200,000us-gaap_UnbilledContractsReceivable      
Depreciation expense related to property and equipment       158,110,000us-gaap_Depreciation 134,110,000us-gaap_Depreciation 120,303,000us-gaap_Depreciation    
Construction work-in-progress 69,233,000us-gaap_ConstructionInProgressGross   44,030,000us-gaap_ConstructionInProgressGross 69,233,000us-gaap_ConstructionInProgressGross 44,030,000us-gaap_ConstructionInProgressGross      
Accrued capital expenditures       11,800,000us-gaap_CapitalExpendituresIncurredButNotYetPaid 600,000us-gaap_CapitalExpendituresIncurredButNotYetPaid      
Debt issuance costs related to amendment         3,244,000us-gaap_PaymentsOfDebtIssuanceCosts      
Debt issuance cost write off         200,000us-gaap_WriteOffOfDeferredDebtIssuanceCost      
Capitalized debt issuance costs 7,600,000us-gaap_DeferredFinanceCostsOwnshareLendingArrangementIssuanceCostsGross   7,600,000us-gaap_DeferredFinanceCostsOwnshareLendingArrangementIssuanceCostsGross 7,600,000us-gaap_DeferredFinanceCostsOwnshareLendingArrangementIssuanceCostsGross 7,600,000us-gaap_DeferredFinanceCostsOwnshareLendingArrangementIssuanceCostsGross      
Accumulated amortization of debt issuance costs 3,500,000us-gaap_DeferredFinanceCostsOwnshareLendingArrangementIssuanceCostsAccumulatedAmortization   2,400,000us-gaap_DeferredFinanceCostsOwnshareLendingArrangementIssuanceCostsAccumulatedAmortization 3,500,000us-gaap_DeferredFinanceCostsOwnshareLendingArrangementIssuanceCostsAccumulatedAmortization 2,400,000us-gaap_DeferredFinanceCostsOwnshareLendingArrangementIssuanceCostsAccumulatedAmortization      
Amortization expense related to capitalized debt issuance costs       1,094,000us-gaap_AmortizationOfFinancingCosts 1,081,000us-gaap_AmortizationOfFinancingCosts 904,000us-gaap_AmortizationOfFinancingCosts    
Decrease in fair value of reporting units considered for impairment calculation 10.00%pwr_DecreaseInFairValueOfReportingUnitsConsideredForImpairmentCalculation     10.00%pwr_DecreaseInFairValueOfReportingUnitsConsideredForImpairmentCalculation        
Gain on sale of equity ownership interest, Pre tax     112,700,000us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal          
Percent change in contract estimates impact on operating results is less than this percentage       5.00%pwr_PercentChangeInContractEstimatesImpactOnOperatingResultsIsLessThanThisPercentage        
Change orders and/or claims 106,800,000us-gaap_UnapprovedChangeOrdersAmount   75,500,000us-gaap_UnapprovedChangeOrdersAmount 106,800,000us-gaap_UnapprovedChangeOrdersAmount 75,500,000us-gaap_UnapprovedChangeOrdersAmount      
Fiber Optic Licensing Terms, Minimum in years       5 years 5 years      
Fiber Optic Licensing Terms, Maximum in years       25 years 25 years      
Fiber optic deferred revenue 56,500,000us-gaap_DeferredRevenue   48,800,000us-gaap_DeferredRevenue 56,500,000us-gaap_DeferredRevenue 48,800,000us-gaap_DeferredRevenue      
Fiber optic non-current deferred revenue 48,200,000us-gaap_DeferredRevenueNoncurrent   40,200,000us-gaap_DeferredRevenueNoncurrent 48,200,000us-gaap_DeferredRevenueNoncurrent 40,200,000us-gaap_DeferredRevenueNoncurrent      
Total amount of unrecognized tax benefits relating to uncertain tax positions 51,079,000us-gaap_UnrecognizedTaxBenefits   48,838,000us-gaap_UnrecognizedTaxBenefits 51,079,000us-gaap_UnrecognizedTaxBenefits 48,838,000us-gaap_UnrecognizedTaxBenefits 51,244,000us-gaap_UnrecognizedTaxBenefits   47,379,000us-gaap_UnrecognizedTaxBenefits
Amount of unrecognized tax benefits change from year-end relating to uncertain tax positions       2,200,000us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease        
Unrecognized tax benefits increases resulting from current period tax positions       9,179,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions 9,073,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions 15,411,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions    
Unrecognized tax benefits increases resulting from prior period tax positions       2,438,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions   1,607,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions    
Unrecognized tax benefits decreases resulting from prior period tax positions       9,376,000us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations 11,479,000us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations 11,965,000us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations    
Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months upper bound 10,331,000us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleEstimatedRangeOfChangeUpperBound   6,722,000us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleEstimatedRangeOfChangeUpperBound 10,331,000us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleEstimatedRangeOfChangeUpperBound 6,722,000us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleEstimatedRangeOfChangeUpperBound 11,479,000us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleEstimatedRangeOfChangeUpperBound    
Employer's liability claims subject to deductible per occurrence       1,000,000pwr_EmployersLiabilityInsuranceClaimsDeductible 1,000,000pwr_EmployersLiabilityInsuranceClaimsDeductible      
General liability insurance claims deductible       10,000,000pwr_GeneralLiabilityInsuranceClaimsDeductible 10,000,000pwr_GeneralLiabilityInsuranceClaimsDeductible      
Worker's compensation claims per occurrence       5,000,000pwr_WorkersCompensationInsuranceClaimsDeductible 5,000,000pwr_WorkersCompensationInsuranceClaimsDeductible      
Auto liability insurance claims deductible       10,000,000pwr_AutoLiabilityInsuranceClaimsDeductible 10,000,000pwr_AutoLiabilityInsuranceClaimsDeductible      
Employee health care benefit plans subject to deductible per claimant       375,000pwr_HealthCareDeductible        
Restricted Stock Units to be Settled in Cash [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Number of common stock shares that may be received by RSU holder       1pwr_NumberOfCommonStockSharesReceivedByRsuHolder
/ us-gaap_AwardTypeAxis
= pwr_RestrictedStockUnitsToBeSettledInCashMember		        
Investments in Joint Ventures [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Cash and cash equivalents 19,100,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ invest_InvestmentAxis
= pwr_InvestmentsInJointVenturesMember		   18,900,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ invest_InvestmentAxis
= pwr_InvestmentsInJointVenturesMember		 19,100,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ invest_InvestmentAxis
= pwr_InvestmentsInJointVenturesMember		 18,900,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ invest_InvestmentAxis
= pwr_InvestmentsInJointVenturesMember		      
Howard Midstream Energy Partners, LLC. [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Proceeds from sale of equity ownership interest             220,900,000us-gaap_ProceedsFromSalesOfBusinessAffiliateAndProductiveAssets
/ dei_LegalEntityAxis
= pwr_HowardMidstreamEnergyPartnersLlcMember		  
Gain on sale of equity ownership interest, Pre tax             112,700,000us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal
/ dei_LegalEntityAxis
= pwr_HowardMidstreamEnergyPartnersLlcMember		  
Equity ownership percentage held             31.00%us-gaap_SubsidiaryOrEquityMethodInvesteeCumulativePercentageOwnershipAfterAllTransactions
/ dei_LegalEntityAxis
= pwr_HowardMidstreamEnergyPartnersLlcMember		  
Fiber Optic Licensing Division [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Construction work-in-progress 30,600,000us-gaap_ConstructionInProgressGross
/ us-gaap_StatementBusinessSegmentsAxis
= pwr_FiberOpticLicensingMember		   32,400,000us-gaap_ConstructionInProgressGross
/ us-gaap_StatementBusinessSegmentsAxis
= pwr_FiberOpticLicensingMember		 30,600,000us-gaap_ConstructionInProgressGross
/ us-gaap_StatementBusinessSegmentsAxis
= pwr_FiberOpticLicensingMember		 32,400,000us-gaap_ConstructionInProgressGross
/ us-gaap_StatementBusinessSegmentsAxis
= pwr_FiberOpticLicensingMember		      
Sunrise Powerlink Project [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Provision for long-term contract receivable 49,900,000pwr_ProvisionForLongtermContractReceivable
/ us-gaap_TypeOfArrangementAxis
= pwr_SunrisePowerlinkProjectMember		 52,500,000pwr_ProvisionForLongtermContractReceivable
/ us-gaap_TypeOfArrangementAxis
= pwr_SunrisePowerlinkProjectMember		   102,500,000pwr_ProvisionForLongtermContractReceivable
/ us-gaap_TypeOfArrangementAxis
= pwr_SunrisePowerlinkProjectMember		        
Contract receivable 65,000,000us-gaap_ContractsReceivableClaimsAndUncertainAmountsExpectedToBeCollectedInRemainderOfFiscalYear
/ us-gaap_TypeOfArrangementAxis
= pwr_SunrisePowerlinkProjectMember		     65,000,000us-gaap_ContractsReceivableClaimsAndUncertainAmountsExpectedToBeCollectedInRemainderOfFiscalYear
/ us-gaap_TypeOfArrangementAxis
= pwr_SunrisePowerlinkProjectMember		        
Long term receivable     165,000,000us-gaap_LongTermInvestmentsAndReceivablesNet
/ us-gaap_TypeOfArrangementAxis
= pwr_SunrisePowerlinkProjectMember		   165,000,000us-gaap_LongTermInvestmentsAndReceivablesNet
/ us-gaap_TypeOfArrangementAxis
= pwr_SunrisePowerlinkProjectMember		      
Domestic Bank Accounts [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Cash and cash equivalents 127,200,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_DomesticBankAccountsMember		   236,700,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_DomesticBankAccountsMember		 127,200,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_DomesticBankAccountsMember		 236,700,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_DomesticBankAccountsMember		      
Foreign Bank Accounts [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Cash and cash equivalents $ 63,300,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_ForeignBankAccountsMember		   $ 252,100,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_ForeignBankAccountsMember		 $ 63,300,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_ForeignBankAccountsMember		 $ 252,100,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_ForeignBankAccountsMember		      
Minimum [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Equity method investment ownership 20.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		     20.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		        
Minimum [Member] | Restricted Stock Units to be Settled in Cash [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Vesting period for restricted stock units to be settled in cash       2 years        
Minimum [Member] | Fiber Optic Licensing Division [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Annual growth rates by reporting units       4.00%pwr_GrowthRate
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_StatementBusinessSegmentsAxis
= pwr_FiberOpticLicensingMember		        
Minimum [Member] | Electric Power and Oil and Gas Services Divisions [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Annual growth rates by reporting units       0.00%pwr_GrowthRate
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_StatementBusinessSegmentsAxis
= pwr_ElectricPowerAndOilAndGasDivisionsMember		        
Maximum [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Equity method investment ownership 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		     50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		        
Maximum [Member] | Restricted Stock Units to be Settled in Cash [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Vesting period for restricted stock units to be settled in cash       3 years        
Maximum [Member] | Fiber Optic Licensing Division [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Annual growth rates by reporting units       12.00%pwr_GrowthRate
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_StatementBusinessSegmentsAxis
= pwr_FiberOpticLicensingMember		        
Maximum [Member] | Electric Power and Oil and Gas Services Divisions [Member]                
Summary Of Significant Accounting Policies [Line Items]                
Annual growth rates by reporting units       71.00%pwr_GrowthRate
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_StatementBusinessSegmentsAxis
= pwr_ElectricPowerAndOilAndGasDivisionsMember