Earnings Per Common Share - Computation of Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 40,131	$ 34,831	$ 80,474	$ 69,355
Less: Preferred stock dividends	2,010	2,010	4,020	4,332
Net income available to common stockholders	$ 38,121	$ 32,821	$ 76,454	$ 65,023
Basic weighted average common shares outstanding	174,940,911	166,185,080	174,548,775	164,196,783
Net effect of dilutive stock options, warrants, restricted stock and convertible debt	1,420,929	1,682,528	1,547,420	1,731,577
Diluted weighted average common shares outstanding	176,361,840	167,867,608	176,096,195	165,928,360
Basic	$ 0.22	$ 0.20	$ 0.44	$ 0.40
Diluted	$ 0.22	$ 0.20	$ 0.43	$ 0.39