Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock [Member]
Cumulative effect of accounting change	$ (29,252)				$ (29,252)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	3,882,416	$ 144,486	$ 642	$ 983,250	2,638,282	$ 267,370	$ (151,614)
Total shareholders’ equity at beginning of period at Dec. 31, 2019	3,911,668	144,486	642	983,250	2,667,534	267,370	(151,614)
Net income	54,753				54,753
Other comprehensive income (loss)	96,445					96,445
Stock option exercises/stock unit conversions (513,824 shares YTD in 2021 and 66,215 shares YTD in 2020)	1,463				(4,983)		6,446
Stock compensation expense recognized in earnings	2,512			2,512
Preferred stock, redemption amount (6,000,000 shares)	(150,000)	(144,486)			(5,514)
Purchase of treasury stock (11,625 shares YTD in 2021 and 181,825 shares YTD in 2020)	(13,973)						(13,973)
Treasury stock issued to the 401(k) stock purchase plan (18,555 shares YTD in 2021)	0
Cash dividends – preferred stock (approximately $14.34 per share which is equivalent to approximately $0.36 per depository share YTD in 2021 and $0.34 per share YTD in 2020)	(2,016)				(2,016)
Cash dividends – common stock ($0.72 per share YTD in 2021 and $0.71 per share YTD in 2020)	(44,934)				(44,934)
Total shareholders’ equity at end of period at Mar. 31, 2020	3,826,666	0	642	985,762	2,635,588	363,815	(159,141)
Total shareholders’ equity at beginning of period at Dec. 31, 2020	4,293,016	145,452	642	997,168	2,750,723	512,970	(113,939)
Net income	116,015				116,015
Other comprehensive income (loss)	(125,222)					(125,222)
Stock option exercises/stock unit conversions (513,824 shares YTD in 2021 and 66,215 shares YTD in 2020)	29,397				(21,342)		50,739
Stock compensation expense recognized in earnings	2,526			2,526
Purchase of treasury stock (11,625 shares YTD in 2021 and 181,825 shares YTD in 2020)	(1,288)						(1,288)
Treasury stock issued to the 401(k) stock purchase plan (18,555 shares YTD in 2021)	1,749				(57)		1,806
Cash dividends – preferred stock (approximately $14.34 per share which is equivalent to approximately $0.36 per depository share YTD in 2021 and $0.34 per share YTD in 2020)	(2,151)				(2,151)
Cash dividends – common stock ($0.72 per share YTD in 2021 and $0.71 per share YTD in 2020)	(46,124)				(46,124)
Total shareholders’ equity at end of period at Mar. 31, 2021	$ 4,267,918	$ 145,452	$ 642	$ 999,694	$ 2,797,064	$ 387,748	$ (62,682)