Earnings (Loss) Per Share - Basic and Diluted Loss Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Basic and Diluted Earnings Per Common Share:
Net income	$ 22,516	$ 2,265
Less: distributed and undistributed earnings allocated to participating securities	(375)	(160)
Net income attributable to common stockholders	$ 22,141	$ 2,105
Basic weighted-average shares outstanding	48,342,145	47,311,840
Dilutive effect of common stock equivalents	580,190	71,081
Diluted weighted-average common shares outstanding	48,922,335	47,382,921
Basic Earnings Per Common Share	$ 0.46	$ 0.04
Diluted Earnings Per Common Share	$ 0.45	$ 0.04