Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands		Total	Preferred Stock [Member]	Common Stock [Member]	Common Stock Issuable [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series A Warrants [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net [Member]	Treasury Stock [Member]	Treasury Stock [Member] Series A Warrants [Member]
Beginning balance at Dec. 31, 2017		$ 16,250,819	$ 1,231,500	$ 79,909	$ 1,847	$ 6,590,855		$ 10,164,804	$ (363,814)	$ (1,454,282)
Cumulative effect of change in accounting principle — equity securities		(16,853)						16,853	(16,853)
Total comprehensive income		708,496						845,770	(137,274)
Preferred stock cash dividends	[1]	(36,260)						(36,260)
Exercise of stock warrants into common stock							$ (5,123)				$ 5,123
Purchases of treasury stock		(1,196,062)								(1,196,062)
Stock-based compensation plans:
Compensation expense, net		15,446		(25)		(6,194)				21,665
Exercises of stock options, net		50,671				(2,402)				53,073
Stock purchase plan		11,124				2,358				8,766
Directors’ stock plan		1,192				149				1,043
Deferred compensation plans, net, including dividend equivalents		(49)			(156)	(248)		(37)		392
Common stock cash dividends		(227,492)						(227,492)
Ending balance at Jun. 30, 2018		15,577,885	1,231,500	79,884	1,691	6,579,395		10,763,638	(517,941)	(2,560,282)
Beginning balance at Mar. 31, 2018		15,709,694	1,231,500	79,884	1,675	6,572,281		10,404,458	(483,243)	(2,096,861)
Total comprehensive income		458,462						493,160	(34,698)
Preferred stock cash dividends	[1]	(18,130)						(18,130)
Exercise of stock warrants into common stock							$ (1,668)				$ 1,668
Purchases of treasury stock		(475,096)								(475,096)
Stock-based compensation plans:
Compensation expense, net		9,613				9,168				445
Exercises of stock options, net		8,571				(457)				9,028
Directors’ stock plan		603				75				528
Deferred compensation plans, net, including dividend equivalents		(1)			16	(4)		(19)		6
Common stock cash dividends		(115,831)						(115,831)
Ending balance at Jun. 30, 2018		15,577,885	1,231,500	79,884	1,691	6,579,395		10,763,638	(517,941)	(2,560,282)
Beginning balance at Dec. 31, 2018		15,460,191	1,231,500	79,883	1,726	6,579,342		11,516,672	(420,081)	(3,528,851)
Total comprehensive income		1,263,125						956,002	307,123
Preferred stock cash dividends	[1]	(36,260)						(36,260)
Purchases of treasury stock		(767,612)								(767,612)
Stock-based compensation plans:
Compensation expense, net		28,855		(12)		1,531				27,336
Exercises of stock options, net		4,727				(2,818)				7,545
Stock purchase plan		11,832				(67)				11,899
Directors’ stock plan		1,068				(116)				1,184
Deferred compensation plans, net, including dividend equivalents		(64)			(200)	(327)		(43)		506
Performance share unit dividends						58		(58)
Common stock cash dividends		(274,035)						(274,035)
Ending balance at Jun. 30, 2019		15,691,827	1,231,500	79,871	1,526	6,577,603		12,162,278	(112,958)	(4,247,993)
Beginning balance at Mar. 31, 2019		15,587,529	1,231,500	79,871	1,514	6,568,480		11,842,371	(288,009)	(3,848,198)
Total comprehensive income		648,311						473,260	175,051
Preferred stock cash dividends	[1]	(18,130)						(18,130)
Purchases of treasury stock		(401,984)								(401,984)
Stock-based compensation plans:
Compensation expense, net		10,735				9,137				1,598
Directors’ stock plan		539				(32)				571
Deferred compensation plans, net, including dividend equivalents					12	(11)		(21)		20
Performance share unit dividends						29		(29)
Common stock cash dividends		(135,173)						(135,173)
Ending balance at Jun. 30, 2019		$ 15,691,827	$ 1,231,500	$ 79,871	$ 1,526	$ 6,577,603		$ 12,162,278	$ (112,958)	$ (4,247,993)

[1] For each of the three-month periods ended June 30, 2019 and 2018, dividends per preferred share were: Preferred Series A- $15.9375; Preferred Series C - $15.9375; Preferred Series E - $16.125; and Preferred Series F - $128.125. For each of the six-month periods ended June 30, 2019 and 2018, dividends per preferred share were: Preferred Series A- $31.875; Preferred Series C - $31.875; Preferred Series E - $32.25; and Preferred Series F - $256.25.