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, 2019	Mar. 31, 2018
Earnings Per Common Share - Basic:
Net income	$ 100,131	$ 63,621
Less: Preferred stock dividends	3,598	3,598
Less: Dividends and undistributed earnings allocated to unvested restricted shares	933	639
Net income allocated to common shareholders - basic	$ 95,600	$ 59,384
Weighted average common shares outstanding	54,177	53,616
Earnings per common share - basic (in usd per share)	$ 1.76	$ 1.11
Earnings Per Common Share - Diluted:
Net income allocated to common shareholders - basic	$ 95,600	$ 59,384
Adjustment for undistributed earnings allocated to unvested restricted shares	(42)	(18)
Net income allocated to common shareholders - diluted	$ 95,558	$ 59,366
Weighted average common shares outstanding	54,177	53,616
Dilutive potential common shares	362	351
Weighted average common shares outstanding - diluted	54,539	53,967
Earnings per common share - diluted (in usd per share)	$ 1.75	$ 1.10