Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings per common share - basic
Net Income	$ 50,810	$ 30,836	$ 93,579	$ 55,962
Preferred stock dividends	(854)	0	(3,430)	0
Dividends and undistributed earnings allocated to unvested restricted shares	(540)	(355)	(1,003)	(675)
Earnings Allocated to Common Shareholders - Basic	$ 49,416	$ 30,481	$ 89,146	$ 55,287
Weighted average common shares outstanding (in shares)	40,771	38,546	40,741	35,871
Earnings per common share - Basic (in usd per share)	$ 1.21	$ 0.79	$ 2.19	$ 1.54
Earnings per common share - diluted
Earnings Allocated to Common Shareholders - Basic	$ 49,416	$ 30,481	$ 89,146	$ 55,287
Dividends and undistributed earnings allocated to unvested restricted shares	(12)	(9)	(13)	(31)
Earnings allocated to common shareholders - diluted	$ 49,404	$ 30,472	$ 89,133	$ 55,256
Weighted average common shares outstanding (in shares)	40,771	38,546	40,741	35,871
Dilutive potential common shares - stock options (in shares)	137	121	86	103
Weighted average common shares outstanding - diluted (in shares)	40,908	38,667	40,827	35,974
Earnings per common share - Diluted (in usd per share)	$ 1.21	$ 0.79	$ 2.18	$ 1.54