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 $) In Thousands, except Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Net income	$ 21,490	$ 22,024	$ 33,466	$ 13,065	$ 7,079	$ 8,320	$ 2,748	$ (3,115)	$ 105,189	$ 6,999	$ 2,283	$ 66,553	$ 90,045	$ 15,032	$ 181,024
Weighted-average shares outstanding													48,394,478	18,520,052	2,345,943
Warrants and options outstanding for the purchase of class A common stock															129,351
Weighted-average shares outstanding, diluted													48,394,478	18,520,052	2,475,294
Per share amount, basic	$ 0.37	$ 0.45	$ 0.70	$ 0.34	$ 0.24	$ 0.29	$ 0.22	$ (1.03)	$ 42.21	$ 3.02	$ 1.00	$ 29.14	$ 1.86	$ 0.81	$ 77.16
Per share amount, diluted	$ 0.37	$ 0.45	$ 0.70	$ 0.34	$ 0.24	$ 0.29	$ 0.22	$ (1.03)	$ 40.65	$ 2.84	$ 0.93	$ 27.39	$ 1.86	$ 0.81	$ 73.13