Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Detail)

v2.4.1.9
Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Dec. 31, 2013
Summary Of Significant Accounting Policies [Line Items]        
Cash and cash equivalents $ 135,534,000us-gaap_CashAndCashEquivalentsAtCarryingValue $ 273,340,000us-gaap_CashAndCashEquivalentsAtCarryingValue $ 190,515,000us-gaap_CashAndCashEquivalentsAtCarryingValue $ 488,777,000us-gaap_CashAndCashEquivalentsAtCarryingValue
Cash equivalents 9,300,000us-gaap_CashEquivalentsAtCarryingValue   107,600,000us-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 6,611,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent   6,174,000us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent  
Current retainage balances 304,900,000us-gaap_ContractReceivableRetainageDueOneYearOrLess   307,300,000us-gaap_ContractReceivableRetainageDueOneYearOrLess  
Non-current retainage balances 24,100,000us-gaap_ContractReceivableRetainageDueAfterOneYear   19,600,000us-gaap_ContractReceivableRetainageDueAfterOneYear  
Unbilled receivables 198,500,000us-gaap_UnbilledContractsReceivable   165,500,000us-gaap_UnbilledContractsReceivable  
Decrease in fair value of reporting units considered for impairment calculation     10.00%pwr_DecreaseInFairValueOfReportingUnitsConsideredForImpairmentCalculation  
Period increase in operating revenue due to change in contract estimates, percentage 8.90%pwr_ChangeInContractEstimatesImpactOnOperatingResults      
Change orders and/or claims 115,800,000us-gaap_UnapprovedChangeOrdersAmount   106,800,000us-gaap_UnapprovedChangeOrdersAmount  
Fiber Optic Licensing Terms, Minimum in years 5 years 5 years 5 years  
Fiber Optic Licensing Terms, Maximum in years 25 years 25 years 25 years  
Fiber optic deferred revenue 57,100,000us-gaap_DeferredRevenue   56,500,000us-gaap_DeferredRevenue  
Fiber optic non-current deferred revenue 48,900,000us-gaap_DeferredRevenueNoncurrent   48,200,000us-gaap_DeferredRevenueNoncurrent  
Total amount of unrecognized tax benefits relating to uncertain tax positions 52,200,000us-gaap_UnrecognizedTaxBenefits      
Amount of unrecognized tax benefits change from year end relating to uncertain tax positions 1,100,000us-gaap_UnrecognizedTaxBenefitsPeriodIncreaseDecrease      
Unrecognized tax benefits increase resulting from current period tax positions 1,600,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions      
Unrecognized tax benefits decrease resulting from settlements with taxing authorities 400,000us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities      
Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months upper bound 10,300,000us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleEstimatedRangeOfChangeUpperBound      
General liability insurance claims deductible 10,000,000pwr_GeneralLiabilityInsuranceClaimsDeductible   10,000,000pwr_GeneralLiabilityInsuranceClaimsDeductible  
Auto liability insurance claims deductible 10,000,000pwr_AutoLiabilityInsuranceClaimsDeductible   10,000,000pwr_AutoLiabilityInsuranceClaimsDeductible  
Worker's compensation claims per occurrence 5,000,000pwr_WorkersCompensationInsuranceClaimsDeductible   5,000,000pwr_WorkersCompensationInsuranceClaimsDeductible 5,000,000pwr_WorkersCompensationInsuranceClaimsDeductible
Employer's liability claims subject to deductible per occurrence 1,000,000pwr_EmployersLiabilityInsuranceClaimsDeductible   1,000,000pwr_EmployersLiabilityInsuranceClaimsDeductible 1,000,000pwr_EmployersLiabilityInsuranceClaimsDeductible
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 17,900,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ invest_InvestmentAxis
= pwr_InvestmentsInJointVenturesMember 		  19,100,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ invest_InvestmentAxis
= pwr_InvestmentsInJointVenturesMember 		 
Domestic Bank Accounts [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Cash and cash equivalents 103,800,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_DomesticBankAccountsMember 		  127,200,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_DomesticBankAccountsMember 		 
Foreign Bank Accounts [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Cash and cash equivalents $ 31,700,000us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_CashAndCashEquivalentsAxis
= pwr_ForeignBankAccountsMember 		  $ 63,300,000us-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 		     
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      
Maximum [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Equity method investment ownership 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