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, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings (loss) per common share-basic
Net income (loss)	$ 2,799	$ (59,066)	$ 34,601	$ (46,248)
Less: Preferred stock dividends	(2,625)	(2,625)	(5,250)	(5,250)
Net income (loss) allocable to common shareholders	174	(61,691)	29,351	(51,498)
Weighted-average common shares outstanding-basic	65,060	64,425	65,021	64,365
Basic earnings (loss) per common share	$ 0.00	$ (0.96)	$ 0.45	$ (0.80)
Earnings (loss) per common share-diluted
Net income (loss)	$ 174	$ (61,691)	$ 34,601	$ (51,498)
Weighted-average common shares outstanding-basic	65,060	64,425	65,021	64,365
Preferred stock weighted-average shares outstanding			19,858
Options, restricted stock and other dilutive securities	52		71
Weighted-average common shares outstanding-diluted	65,112	64,425	84,950	64,365
Diluted earnings (loss) per common share	$ 0.00	$ (0.96)	$ 0.41	$ (0.80)