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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Common Share - Basic:
Net income	$ 101,598	$ 75,124	$ 201,729	$ 138,745
Less: Preferred stock dividends	949	949	4,547	4,547
Less: Dividends and undistributed earnings allocated to unvested restricted shares	999	767	1,931	1,409
Earnings allocated to common shareholders - basic	$ 99,650	$ 73,408	$ 195,251	$ 132,789
Weighted average common shares outstanding	53,345	55,931	53,758	54,780
Earnings per common share - basic (in usd per share)	$ 1.87	$ 1.31	$ 3.63	$ 2.42
Earnings Per Common Share - Diluted:
Earnings allocated to common shareholders - basic	$ 99,650	$ 73,408	$ 195,251	$ 132,789
Adjustment for undistributed earnings allocated to unvested restricted shares	24	(7)	(21)	(26)
Earnings allocated to common shareholders - diluted	$ 99,674	$ 73,401	$ 195,230	$ 132,763
Weighted average common shares outstanding	53,345	55,931	53,758	54,780
Dilutive potential common shares	328	356	346	353
Weighted average common shares outstanding - diluted	53,674	56,287	54,104	55,133
Earnings per common share - diluted (in usd per share)	$ 1.86	$ 1.30	$ 3.61	$ 2.41