Stockholders' 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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement [Abstract]
Net income (loss)	$ 2,748	$ 2,283	$ (367)	$ 68,836
Weighted average shares outstanding	12,401,274	2,289,352	7,734,774	2,286,582
Warrants and options outstanding for the purchase of class A common stock		153,334		148,757
Weighted average shares outstanding, diluted	12,401,274	2,442,686	7,734,774	2,435,339
Per share amount, basic	$ 0.22	$ 1.00	$ (0.05)	$ 30.10
Per share amount, diluted	$ 0.22	$ 0.93	$ (0.05)	$ 28.27