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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings per common share - basic:
Net income	$ 29,644	$ 48,068	$ 132,135	$ 141,647
Less: Preferred stock dividends	3,598	3,590	8,146	7,020
Less: Dividends and undistributed earnings allocated to unvested restricted shares	283	462	1,052	1,464
Net income allocated to common shareholders - basic	$ 25,763	$ 44,016	$ 122,937	$ 133,163
Weighted average common shares outstanding	52,424	40,618	49,749	40,699
Earnings per common share - basic (in usd per share)	$ 0.49	$ 1.08	$ 2.47	$ 3.27
Earnings per common share - diluted:
Net income allocated to common shareholders - basic	$ 25,763	$ 44,016	$ 122,937	$ 133,163
Adjustment for undistributed earnings allocated to unvested restricted shares	8	(4)	0	(17)
Earnings Allocated to Common Shareholders	$ 25,771	$ 44,012	$ 122,937	$ 133,146
Weighted average common shares outstanding	52,424	40,618	49,749	40,699
Dilutive potential common shares	346	193	357	119
Weighted average common shares outstanding - diluted	52,770	40,811	50,106	40,818
Earnings per common share - diluted (in usd per share)	$ 0.49	$ 1.08	$ 2.45	$ 3.26