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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings per common share - basic:
Net income	$ 101,465	$ 29,644	$ 240,210	$ 132,135
Less: Preferred stock dividends	3,599	3,598	8,146	8,146
Less: Dividends and undistributed earnings allocated to unvested restricted shares	908	283	2,341	1,052
Net income allocated to common shareholders - basic	$ 96,958	$ 25,763	$ 229,723	$ 122,937
Weighted average common shares outstanding	55,571	52,424	55,047	49,749
Earnings per common share - basic (in usd per share)	$ 1.74	$ 0.49	$ 4.17	$ 2.47
Earnings per common share - diluted:
Net income allocated to common shareholders - basic	$ 96,958	$ 25,763	$ 229,723	$ 122,937
Adjustment for undistributed earnings allocated to unvested restricted shares	(25)	8	(49)	0
Net income allocated to common shareholders - diluted	$ 96,933	$ 25,771	$ 229,674	$ 122,937
Weighted average common shares outstanding	55,571	52,424	55,047	49,749
Dilutive potential common shares	374	346	360	357
Weighted average common shares outstanding - diluted	55,945	52,770	55,407	50,106
Earnings per common share - diluted (in usd per share)	$ 1.73	$ 0.49	$ 4.14	$ 2.45