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		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings per common share - basic
Net Income	$ 48,068	$ 42,475	$ 141,647	$ 98,437
Preferred stock dividends	(3,590)	0	(7,020)	0
Dividends and undistributed earnings allocated to unvested restricted shares	(462)	(492)	(1,464)	(1,171)
Earnings Allocated to Common Shareholders - Basic	$ 44,016	$ 41,983	$ 133,163	$ 97,266
Weighted average common shares outstanding (in shares)	40,618	40,514	40,699	37,436
Earnings per common share - Basic (in usd per share)	$ 1.08	$ 1.04	$ 3.27	$ 2.60
Earnings per common share - diluted
Earnings Allocated to Common Shareholders - Basic	$ 44,016	$ 41,983	$ 133,163	$ 97,266
Dividends and undistributed earnings allocated to unvested restricted shares	(4)	(3)	(17)	(41)
Earnings allocated to common shareholders - diluted	$ 44,012	$ 41,980	$ 133,146	$ 97,225
Weighted average common shares outstanding (in shares)	40,618	40,514	40,699	37,436
Dilutive potential common shares - stock options (in shares)	193	100	119	96
Weighted average common shares outstanding - diluted (in shares)	40,811	40,614	40,818	37,532
Earnings per common share - Diluted (in usd per share)	$ 1.08	$ 1.03	$ 3.26	$ 2.59