Equity - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2013
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
Value of treasury stock acquired, cost method	$ 93,482,000
Aggregate authorized amount of common stock to be repurchased	500,000,000
Reduction in net income as a result of non controlling interests	18,368,000	19,388,000	16,027,000
Carrying value of the investments held by Quanta in variable interest entities	11,100,000	7,100,000
Carrying value of the investment held by noncontrolling interest in variable interest entities	11,067,000	7,131,000
Distributions to non-controlling interests	14,432,000	17,625,000	17,970,000
Treasury Stock [Member]
Equity [Line Items]
Treasury stock acquired	2,996,278	0
Value of treasury stock acquired, cost method	93,482,000
Series F Preferred Stock [Member]
Equity [Line Items]
Number of preferred Stock issued to voting trust	1	1
Exchangeable shares exchanged for common stock				409,110
Series G Preferred Stock [Member]
Equity [Line Items]
Number of preferred Stock issued to voting trust	1	0
Exchangeable Shares [Member]
Equity [Line Items]
Exchangeable shares exchanged for common stock		(409,110)
Exchangeable stock shares outstanding	7,325,971
Series F- and Series G- Preferred Stock [Member]
Equity [Line Items]
Exchangeable stock shares outstanding	4,399,858
Common Stock Withheld for Settlement of Employee Tax Liabilities [Member] | Treasury Stock [Member]
Equity [Line Items]
Treasury stock acquired	352,558	379,566	370,007
Value of treasury stock acquired, cost method	$ 12,300,000	$ 12,100,000	$ 6,700,000