Earnings per Common Share - Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings per common share—basic
Net income	$ 10,071	$ 2,799	$ 51,731	$ 34,601
Less: Preferred stock dividends	(783)	(2,625)	(1,566)	(5,250)
Net income allocable to common shareholders	9,288	174	50,165	29,351
Weighted-average common shares outstanding—basic	71,111	65,060	71,086	65,021
Basic earnings per common share	$ 0.13	$ 0.00	$ 0.71	$ 0.45
Earnings per common share—diluted
Net income	10,071	2,799	51,731	34,601
Less: Preferred stock dividends	(783)	(2,625)	(1,566)	(5,250)
Interest on convertible debt, net of tax	1,230	0	2,439	0
Net income including assumed conversions	$ 10,518	$ 174	$ 54,170	$ 34,601
Weighted-average common shares outstanding—basic	71,111	65,060	71,086	65,021
Convertible notes weighted-average shares outstanding	15,000	0	15,000	0
Preferred stock weighted-average shares outstanding	0	0	5,924	19,858
Options, restricted stock and other dilutive securities	238	52	225	71
Weighted-average common shares outstanding—diluted	86,349	65,112	92,235	84,950
Dilutive earnings per common share	$ 0.12	$ 0.00	$ 0.59	$ 0.41