Earnings Per Common Share - Computation of Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 40,053	$ 35,391	$ 120,527	$ 104,746
Less: Preferred stock dividends	2,010	2,010	6,030	6,342
Net income available to common stockholders	$ 38,043	$ 33,381	$ 114,497	$ 98,404
Basic weighted average common shares outstanding	175,343,789	167,260,386	174,816,692	165,229,206
Net effect of dilutive stock options, warrants, restricted stock and convertible debt	1,169,043	1,623,741	1,383,450	1,695,637
Diluted weighted average common shares outstanding	176,512,832	168,884,127	176,200,142	166,924,843
Basic	$ 0.22	$ 0.20	$ 0.65	$ 0.60
Diluted	$ 0.22	$ 0.20	$ 0.65	$ 0.59