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Summary of Significant Accounting Policies - Significant Estimates Used by Management in Determining Fair Values of Company's Reporting Units (Detail) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Electric Power and Oil and Gas Services Divisions [Member] |  |  |
Goodwill Impairment Testing Assumptions [Line Items] |  |  |
Years of cash flows before terminal value | 5 years | 5 years | 5 years
Weighting of three approaches: |  |  |
Discounted cash flows | 70.00%pwr_DiscountedCashFlowsWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 70.00%pwr_DiscountedCashFlowsWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 70.00%pwr_DiscountedCashFlowsWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember
Market multiple | 15.00%pwr_MarketMultipleWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 15.00%pwr_MarketMultipleWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 15.00%pwr_MarketMultipleWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember
Market capitalization | 15.00%pwr_MarketCapitalizationWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 15.00%pwr_MarketCapitalizationWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 15.00%pwr_MarketCapitalizationWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember
Electric Power and Oil and Gas Services Divisions [Member] | Minimum [Member] |  |  |
Goodwill Impairment Testing Assumptions [Line Items] |  |  |
Discount rates | 12.00%pwr_DiscountRates / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 12.00%pwr_DiscountRates / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 12.00%pwr_DiscountRates / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember
EBITDA multiples | 5.0 pwr_EbitdaMultiples / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 5.0 pwr_EbitdaMultiples / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 4.5 pwr_EbitdaMultiples / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember
Electric Power and Oil and Gas Services Divisions [Member] | Maximum [Member] |  |  |
Goodwill Impairment Testing Assumptions [Line Items] |  |  |
Discount rates | 14.00%pwr_DiscountRates / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 14.00%pwr_DiscountRates / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 13.00%pwr_DiscountRates / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember
EBITDA multiples | 6.0 pwr_EbitdaMultiples / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 8.0 pwr_EbitdaMultiples / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember | 8.0 pwr_EbitdaMultiples / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_StatementBusinessSegmentsAxis = pwr_ElectricPowerAndOilAndGasDivisionsMember
Fiber Optic Licensing Division [Member] |  |  |
Goodwill Impairment Testing Assumptions [Line Items] |  |  |
Years of cash flows before terminal value | 15 years | 15 years | 15 years
Discount rates | 12.00%pwr_DiscountRates / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 12.00%pwr_DiscountRates / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 12.00%pwr_DiscountRates / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember
EBITDA multiples | 9.5 pwr_EbitdaMultiples / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 9.5 pwr_EbitdaMultiples / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 9.5 pwr_EbitdaMultiples / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember
Weighting of three approaches: |  |  |
Discounted cash flows | 90.00%pwr_DiscountedCashFlowsWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 90.00%pwr_DiscountedCashFlowsWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 90.00%pwr_DiscountedCashFlowsWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember
Market multiple | 5.00%pwr_MarketMultipleWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 5.00%pwr_MarketMultipleWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 5.00%pwr_MarketMultipleWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember
Market capitalization | 5.00%pwr_MarketCapitalizationWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 5.00%pwr_MarketCapitalizationWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember | 5.00%pwr_MarketCapitalizationWeightedPercentage / us-gaap_StatementBusinessSegmentsAxis = pwr_FiberOpticLicensingMember

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