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
	Mar. 31, 2017	Mar. 31, 2016
Earnings per common share - basic:
Net income	$ 50,473	$ 42,769
Preferred stock dividends	(3,599)	(2,576)
Dividends and undistributed earnings allocated to unvested restricted shares	(346)	(460)
Net income allocated to common shareholders - basic	$ 46,528	$ 39,733
Weighted average common shares outstanding	46,123	40,711
Earnings per common share - basic (in usd per share)	$ 1.01	$ 0.98
Earnings per common share - diluted:
Net income allocated to common shareholders - basic	$ 46,528	$ 39,733
Dividends and undistributed earnings allocated to unvested restricted shares	(37)	(2)
Earnings Allocated to Common Shareholders	$ 46,491	$ 39,731
Weighted average common shares outstanding	46,123	40,711
Dilutive potential common shares	373	54
Weighted average common shares outstanding - diluted	46,496	40,765
Earnings per common share - diluted (in usd per share)	$ 1.00	$ 0.97