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		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings per common share—basic
Net income (loss)	$ (1,134)	$ (21,153)	$ 57,547	$ 30,578
Less: Preferred stock dividends	0	(1,766)	0	(3,332)
Net income (loss) allocable to common shareholders	(1,134)	(22,919)	57,547	27,246
Weighted-average common shares outstanding—basic (in shares)	77,646	72,649	77,551	71,613
Basic earnings per common share (in dollars per share)	$ (0.01)	$ (0.32)	$ 0.74	$ 0.38
Earnings per common share—diluted
Net income (loss)	(1,134)	(21,153)	57,547	30,578
Less: Preferred stock dividends	0	(1,766)	0	(3,332)
Add: Interest on convertible debt, net of tax	0	0	3,715	3,673
Net income including assumed conversions	$ (1,134)	$ (22,919)	$ 61,262	$ 30,919
Weighted-average common shares outstanding—basic (in shares)	77,646	72,649	77,551	71,613
Convertible notes weighted-average shares outstanding	0	0	15,000	15,000
Options, restricted stock and other dilutive securities	0	0	833	257
Weighted-average common shares outstanding—diluted	77,646	72,649	93,384	86,870
Dilutive earnings per common share (in dollars per share)	$ (0.01)	$ (0.32)	$ 0.66	$ 0.36