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)
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, 2019	3,911,668	144,486	642	983,250	2,667,534	267,370	(151,614)
Net income	147,825				147,825
Other comprehensive income (loss)	220,894					220,894
Stock option exercises/stock unit conversions (114,252 shares QTD and 628,076 shares YTD in 2021 and 77,308 shares QTD and 143,523 shares YTD in 2020)	4,846				(9,125)		13,971
Stock compensation expense recognized in earnings	5,784			5,784
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 and 38,943 shares YTD in 2020)	2,830				(961)		3,791
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share QTD and $25.46 per share which is equivalent to approximately $0.64 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 QTD and $1.44 per share YTD in 2021 and $0.71 per share QTD and $1.42 per share YTD in 2020)	(89,805)				(89,805)
Total shareholders’ equity at end of period at Jun. 30, 2020	4,008,801	0	642	989,034	2,678,686	488,264	(147,825)
Total shareholders’ equity at beginning of period at Mar. 31, 2020	3,826,666	0	642	985,762	2,635,588	363,815	(159,141)
Net income	93,072				93,072
Other comprehensive income (loss)	124,449					124,449
Stock option exercises/stock unit conversions (114,252 shares QTD and 628,076 shares YTD in 2021 and 77,308 shares QTD and 143,523 shares YTD in 2020)	3,383				(4,142)		7,525
Stock compensation expense recognized in earnings	3,272			3,272
Treasury stock issued to the 401(k) stock purchase plan (18,555 shares YTD in 2021 and 38,943 shares YTD in 2020)	2,830				(961)		3,791
Cash dividends – common stock ($0.72 per share QTD and $1.44 per share YTD in 2021 and $0.71 per share QTD and $1.42 per share YTD in 2020)	(44,871)				(44,871)
Total shareholders’ equity at end of period at Jun. 30, 2020	4,008,801	0	642	989,034	2,678,686	488,264	(147,825)
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	234,083				234,083
Other comprehensive income (loss)	(99,980)					(99,980)
Stock option exercises/stock unit conversions (114,252 shares QTD and 628,076 shares YTD in 2021 and 77,308 shares QTD and 143,523 shares YTD in 2020)	36,682				(25,567)		62,249
Stock compensation expense recognized in earnings	5,771			5,771
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 and 38,943 shares YTD in 2020)	1,749				(57)		1,806
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share QTD and $25.46 per share which is equivalent to approximately $0.64 per depository share YTD in 2021 and $0.34 per share YTD in 2020)	(3,820)				(3,820)
Cash dividends – common stock ($0.72 per share QTD and $1.44 per share YTD in 2021 and $0.71 per share QTD and $1.42 per share YTD in 2020)	(92,396)				(92,396)
Total shareholders’ equity at end of period at Jun. 30, 2021	4,373,817	145,452	642	1,002,939	2,862,966	412,990	(51,172)
Total shareholders’ equity at beginning of period at Mar. 31, 2021	4,267,918	145,452	642	999,694	2,797,064	387,748	(62,682)
Net income	118,068				118,068
Other comprehensive income (loss)	25,242					25,242
Stock option exercises/stock unit conversions (114,252 shares QTD and 628,076 shares YTD in 2021 and 77,308 shares QTD and 143,523 shares YTD in 2020)	7,285				(4,225)		11,510
Stock compensation expense recognized in earnings	3,245			3,245
Cash dividends – preferred stock (approximately $11.13 per share which is equivalent to approximately $0.28 per depository share QTD and $25.46 per share which is equivalent to approximately $0.64 per depository share YTD in 2021 and $0.34 per share YTD in 2020)	(1,669)				(1,669)
Cash dividends – common stock ($0.72 per share QTD and $1.44 per share YTD in 2021 and $0.71 per share QTD and $1.42 per share YTD in 2020)	(46,272)				(46,272)
Total shareholders’ equity at end of period at Jun. 30, 2021	$ 4,373,817	$ 145,452	$ 642	$ 1,002,939	$ 2,862,966	$ 412,990	$ (51,172)