Quarterly report pursuant to Section 13 or 15(d)

Equity - Additional Information (Detail)

v2.4.1.9
Equity - Additional Information (Detail) (USD $)
3 Months Ended 15 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2015
Dec. 31, 2014
Equity [Line Items]        
Minimum number of shares that can be exchanged by exchangeable shareholders unless the number of remaining exchangeable shares registered in the name of the holder is less 50,000pwr_MinimumNumberOfSharesThatCanBeExchangedByExchangeableShareholdersUnlessNumberOfRemainingExchangeableSharesRegisteredInNameOfHolderIsLess      
Number of shares of Common stock received for each exchangeable share 1pwr_NumberOfSharesOfCommonStockReceivedForEachExchangeableShare      
Shares outstanding 204,495,383us-gaap_CommonStockSharesOutstanding   204,495,383us-gaap_CommonStockSharesOutstanding 210,819,790us-gaap_CommonStockSharesOutstanding
Income attributable to the other joint venture members $ 4,700,000us-gaap_NoncontrollingInterestInNetIncomeLossJointVenturePartnersNonredeemable $ 4,200,000us-gaap_NoncontrollingInterestInNetIncomeLossJointVenturePartnersNonredeemable    
Carrying value of the investments held by Quanta in variable interest entities 13,300,000us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssetsAndLiabilitiesNet   13,300,000us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssetsAndLiabilitiesNet 11,100,000us-gaap_VariableInterestEntityConsolidatedCarryingAmountAssetsAndLiabilitiesNet
Carrying value of the investment held by noncontrolling interest in variable interest entities 13,265,000us-gaap_MinorityInterest   13,265,000us-gaap_MinorityInterest 11,067,000us-gaap_MinorityInterest
Distributions to non-controlling interests 2,500,000us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders 500,000us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders    
Maximum [Member]        
Equity [Line Items]        
Aggregate authorized amount of common stock to be repurchased 500,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
  500,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Treasury Stock [Member]        
Equity [Line Items]        
Treasury stock acquired 6,700,000us-gaap_TreasuryStockSharesAcquired
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember
  9,700,000us-gaap_TreasuryStockSharesAcquired
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember
 
Value of treasury stock acquired, cost method 182,000,000us-gaap_TreasuryStockValueAcquiredCostMethod
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember
  275,500,000us-gaap_TreasuryStockValueAcquiredCostMethod
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember
 
Series F Preferred Stock [Member]        
Equity [Line Items]        
Number of preferred Stock issued to voting trust 1us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesFPreferredStockMember
  1us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesFPreferredStockMember
1us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesFPreferredStockMember
Series G Preferred Stock [Member]        
Equity [Line Items]        
Number of preferred Stock issued to voting trust 1us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesGPreferredStockMember
  1us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesGPreferredStockMember
1us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesGPreferredStockMember
Exchangeable Shares [Member]        
Equity [Line Items]        
Shares outstanding 7,325,971us-gaap_CommonStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_ConvertibleCommonStockMember
  7,325,971us-gaap_CommonStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_ConvertibleCommonStockMember
7,325,971us-gaap_CommonStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_ConvertibleCommonStockMember
Series F- and Series G- Preferred Stock [Member]        
Equity [Line Items]        
Exchangeable stock shares outstanding 4,399,858pwr_ExchangeableStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= pwr_SeriesFAndSeriesGPreferredStockMember
  4,399,858pwr_ExchangeableStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= pwr_SeriesFAndSeriesGPreferredStockMember
 
Common Stock Withheld for Settlement of Employee Tax Liabilities [Member] | Treasury Stock [Member]        
Equity [Line Items]        
Treasury stock acquired 300,000us-gaap_TreasuryStockSharesAcquired
/ us-gaap_StatementClassOfStockAxis
= pwr_CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember
300,000us-gaap_TreasuryStockSharesAcquired
/ us-gaap_StatementClassOfStockAxis
= pwr_CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember
   
Value of treasury stock acquired, cost method $ 9,500,000us-gaap_TreasuryStockValueAcquiredCostMethod
/ us-gaap_StatementClassOfStockAxis
= pwr_CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember
$ 11,400,000us-gaap_TreasuryStockValueAcquiredCostMethod
/ us-gaap_StatementClassOfStockAxis
= pwr_CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_TreasuryStockMember