Equity (Non-controlling Interests) - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Noncontrolling Interest [Abstract]
Income attributable to the other joint venture members	$ 200,000	$ 3,500,000	$ 500,000	$ 8,200,000
Carrying value of the investments held by Quanta in variable interest entities	2,900,000		2,900,000		$ 2,300,000
Non-controlling interests	2,851,000		2,851,000		$ 2,321,000
Distributions to non-controlling interests	$ 0	$ 2,500,000	$ 0	$ 5,000,000