Equity - Schedule of Calculation of Basic and Diluted Earnings Per Share of Class A Common Stock Based on Weighted-Average of Both Restricted and Unrestricted Class A Common Stock Outstanding (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Equity [Abstract]
Net income	$ 22,024	$ 8,320	$ 68,555	$ 7,953
Weighted-average shares outstanding, basic and diluted	49,211,205	28,894,515	45,093,314	14,865,530
Per share amount, basic and diluted	$ 0.45	$ 0.29	$ 1.52	$ 0.53