Basic and Diluted Earnings (Loss) Per Common Share - Schedule of Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic:
Net income available to common shareholders	$ 44,204	$ (490)	$ 47,328	$ (3,761)
Average basic shares outstanding	94,029,583	93,777,662	93,983,629	93,688,003
Basic earnings per share	$ 0.47	$ (0.01)	$ 0.50	$ (0.04)
Diluted:
Net income available to common shareholders	$ 44,204	$ (490)	$ 47,328	$ (3,761)
Average basic shares outstanding	94,029,583	93,777,662	93,983,629	93,688,003
Employee restricted stock	1,460,570	704,335	952,413	755,212
Average diluted shares outstanding	95,490,153	94,481,997	94,936,042	94,443,215
Diluted earnings per share	$ 0.46	$ (0.01)	$ 0.50	$ (0.04)