Earnings Per Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income									$ 37,773	$ 145,420	$ 9,642
Noncontrolling interests									(101)
Preferred stockholder dividends										(9,482)	(3,289)
Allocation of earnings to preferred stockholders									(64)	(24,260)	(1,144)
Net Income Attributable to Common Stockholders									$ 37,608	$ 111,678	$ 5,209
Basic: Weighted-average number of shares outstanding									7,727	6,211	6,014
Plus: Incremental shares from assumed conversion of dilutive instruments									346	623	423
Diluted: Weighted-average number of shares outstanding									8,073	6,834	6,437
Earnings (Loss) per share-Basic	$ 1.56	$ 1.48	$ 1.08	$ 0.72	$ 17.60	$ (0.56)	$ 0.33	$ 0.48	$ 4.87	$ 17.98	$ 0.87
Earnings (Loss) per share-Diluted	$ 1.50	$ 1.43	$ 1.04	$ 0.68	$ 16.35	$ (0.56)	$ 0.30	$ 0.43	$ 4.66	$ 16.34	$ 0.81