Equity - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 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	$ 4,776,000	$ 4,287,000
Carrying value of the investments held by Quanta in variable interest entities	4,700,000		5,400,000
Distributions to noncontrolling interests	5,500,000	2,500,000
Carrying value of the investment held by noncontrolling interest in variable interest entities	4,690,000		5,368,000
Series F Preferred Stock [Member]
Stockholders Equity [Line Items]
Number of preferred Stock issued to voting trust	1
Common Stock Withheld for Settlement of Employee Tax Liabilities [Member]
Stockholders Equity [Line Items]
Treasury stock acquired	296,874	283,366
Value of treasury stock acquired, cost method	$ 9,700,000	$ 6,000,000