Equity - Schedule of Basic and Diluted Earnings Per Share, or EPS, Based on the 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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 8,320	$ 6,999	$ 7,953	$ 75,835
Weighted-average shares outstanding	28,894,515	2,317,343	14,865,530	2,296,910
Warrants and options outstanding for the purchase of class A common stock		144,260		147,296
Weighted-average shares outstanding, diluted	28,894,515	2,461,603	14,865,530	2,444,206
Per share amount, basic	$ 0.29	$ 3.02	$ 0.53	$ 33.02
Per share amount, diluted	$ 0.29	$ 2.84	$ 0.53	$ 31.03