Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net of Tax [Member]	Treasury Stock [Member]
Balance at Dec. 31, 2016	$ 3,002,528	$ 144,486	$ 637	$ 906,732	$ 1,985,569	$ (24,623)	$ (10,273)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	364,149				364,149
Other comprehensive loss, net of tax	104,135					104,135
Proceeds from stock option exercises/stock unit conversions (399,244 shares, 548,238 shares, and 1,150,920 shares during 2019, 2018, and 2017, respectively)	67,746		5	33,616	(10,414)		44,539
Stock-based compensation expense recognized in earnings	13,013			13,013
Purchase of treasury stock (716,062 shares,1,037,982 shares, and 1,149,555 shares during 2019, 2018, and 2017, respectively)	(101,473)						(101,473)
Cash dividends paid on preferred stock (approximately $1.34 per share in 2019, 2018, and 2017)	(8,063)				(8,063)
Cash dividends – common stock ($2.80 per share, $2.58 per share, and $2.25 per share in 2019, 2018, and 2017, respectively)	(144,172)				(144,172)
Balance at Dec. 31, 2017	3,297,863	144,486	642	953,361	2,187,069	79,512	(67,207)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting principle in period of adoption	(2,285)				(2,285)
Stockholders' Equity, as adjusted at the beginning of period	3,295,578	144,486	642	953,361	2,184,784	79,512	(67,207)
Net income	454,918				454,918
Other comprehensive loss, net of tax	(152,647)					(152,647)
Reclassification of certain income tax effects related to U.S. statutory federal income tax rate under the Tax Cuts and Jobs Act					(9,535)	9,535
Proceeds from stock option exercises/stock unit conversions (399,244 shares, 548,238 shares, and 1,150,920 shares during 2019, 2018, and 2017, respectively)	31,647				(16,653)		48,300
Stock-based compensation expense recognized in earnings	13,943			13,943
Purchase of treasury stock (716,062 shares,1,037,982 shares, and 1,149,555 shares during 2019, 2018, and 2017, respectively)	(101,010)						(101,010)
Cash dividends paid on preferred stock (approximately $1.34 per share in 2019, 2018, and 2017)	(8,063)				(8,063)
Cash dividends – common stock ($2.80 per share, $2.58 per share, and $2.25 per share in 2019, 2018, and 2017, respectively)	(165,449)				(165,449)
Balance at Dec. 31, 2018	3,368,917	144,486	642	967,304	2,440,002	(63,600)	(119,917)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of new accounting principle in period of adoption	(14,672)				(14,672)
Stockholders' Equity, as adjusted at the beginning of period	3,354,245	144,486	642	967,304	2,425,330	(63,600)	(119,917)
Net income	443,599				443,599
Other comprehensive loss, net of tax	330,970					330,970
Proceeds from stock option exercises/stock unit conversions (399,244 shares, 548,238 shares, and 1,150,920 shares during 2019, 2018, and 2017, respectively)	20,770				(16,326)		37,096
Stock-based compensation expense recognized in earnings	15,946			15,946
Purchase of treasury stock (716,062 shares,1,037,982 shares, and 1,149,555 shares during 2019, 2018, and 2017, respectively)	(68,793)						(68,793)
Cash dividends paid on preferred stock (approximately $1.34 per share in 2019, 2018, and 2017)	(8,063)				(8,063)
Cash dividends – common stock ($2.80 per share, $2.58 per share, and $2.25 per share in 2019, 2018, and 2017, respectively)	(177,006)				(177,006)
Balance at Dec. 31, 2019	$ 3,911,668	$ 144,486	$ 642	$ 983,250	$ 2,667,534	$ 267,370	$ (151,614)