Quarterly report pursuant to Section 13 or 15(d)

Equity - Additional Information (Detail)

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Equity - Additional Information (Detail) (USD $)
 3 Months Ended 6 Months Ended
Jun. 30, 2013
Mar. 31, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Dec. 31, 2012
Stockholders 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       50,000    
Number of shares of Common stock received for each exchangeable share       1    
Exchangeable shares exchanged for common stock   409,110        
Reduction in net income as a result of non controlling interests $ 4,489,000   $ 4,259,000 $ 9,265,000 $ 8,546,000  
Carrying value of the investments held by Quanta in variable interest entities 5,300,000     5,300,000   5,400,000
Distributions to noncontrolling interests 3,900,000   3,700,000 9,300,000 6,200,000  
Carrying value of the investment held by noncontrolling interest in variable interest entities 5,321,000     5,321,000   5,368,000
Common Stock Withheld for Settlement of Employee Tax Liabilities [Member]
            
Stockholders Equity [Line Items]            
Treasury stock acquired       372,015 286,954  
Value of treasury stock acquired, cost method       $ 11,900,000 $ 6,100,000  
Series F Preferred Stock [Member]
            
Stockholders Equity [Line Items]            
Number of preferred Stock issued to voting trust 1     1