Equity - Schedule of Basic and Diluted Earnings Per Share, or EPS, Based on Weighted-Average of Both Restricted and Unrestricted Class A Common Stock Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 66,888	$ 22,024	$ 131,564	$ 68,555
Weighted-average shares outstanding, basic and diluted	93,357,960	49,211,205	77,752,247	45,093,314
Per share amount, basic and diluted	$ 0.72	$ 0.45	$ 1.69	$ 1.52