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Equity-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
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
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
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	$ 3.9us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = pwr_RestrictedStockUnitsToBeSettledInCashMember	$ 3.1us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = pwr_RestrictedStockUnitsToBeSettledInCashMember	$ 2.0us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = pwr_RestrictedStockUnitsToBeSettledInCashMember
Payment to settle liabilities under compensation plan	3.1us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards / us-gaap_AwardTypeAxis = pwr_RestrictedStockUnitsToBeSettledInCashMember	1.8us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards / us-gaap_AwardTypeAxis = pwr_RestrictedStockUnitsToBeSettledInCashMember	1.7us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards / us-gaap_AwardTypeAxis = pwr_RestrictedStockUnitsToBeSettledInCashMember
Accrued liabilities under Compensation Plan	2.9us-gaap_DeferredCompensationShareBasedArrangementsLiabilityCurrent / us-gaap_AwardTypeAxis = pwr_RestrictedStockUnitsToBeSettledInCashMember	2.1us-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	1,400,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember	1,500,000us-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	$ 35.09us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember	$ 29.37us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember	$ 21.84us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
Awards vested	1,100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember	1,200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember	900,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
Fair value of restricted stock, vested	33.5us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember	32.8us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember	22.3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
Compensation costs		4.3us-gaap_EmployeeBenefitsAndShareBasedCompensation / us-gaap_AwardTypeAxis = pwr_RestrictedStockAndRestrictedStockUnitsToBeSettledInCommonStockMember
Unrecognized compensation cost, related to unvested restricted stock, total	34.5us-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)	1 year 6 months 22 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	100,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember	0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember	0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Granted, weighted average grant date fair value, per share	$ 35.20us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Awards vested	0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Compensation costs	$ 2.4us-gaap_EmployeeBenefitsAndShareBasedCompensation / 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 financial targets and strategic goals on a 0% to 200% performance scale as determined by the Compensation Committee.
Number of common shares distributed 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

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Common stock available for awards pursuant to the plan.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements payable within one year (or the operating cycle, if longer).

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Costs and payments related to employee benefits and equity-based compensation, such as pension expense and contributions, other postretirement benefits expense and payments, stock or unit options expense, and amortization of restricted stock or unit.

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Aggregate cash paid by the entity during the period to settle equity instruments granted under equity-based payment arrangements.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Number of share instruments newly issued under a share-based compensation plan.

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Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements.

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