Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Series A And Series C [Member]	Series G Preferred Stock [Member]	Preferred Stock [Member]	Preferred Stock [Member] Series A And Series C [Member]	Preferred Stock [Member] Series G Preferred Stock [Member]	Common Stock [Member]	Common Stock Issuable [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series G Preferred Stock [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	1,210,129											1,371,861	(161,732)
Preferred stock cash dividends	(54,390)											(54,390)
Exercise of stock warrants into common stock											$ (7,240)				$ 7,240
Purchases of treasury stock	(1,694,562)													(1,694,562)
Stock-based compensation plans:
Compensation expense, net	25,148						(26)		2,836					22,338
Stock purchase plan	11,124								2,358					8,766
Exercises of stock options, net	56,793								(3,282)					60,075
Directors’ stock plan	1,796								168					1,628
Deferred compensation plans, net, including dividend equivalents	(49)							(131)	(248)			(62)		392
Common stock cash dividends	(370,723)											(370,723)
Ending balance at Sep. 30, 2018	15,436,085			1,231,500			79,883	1,716	6,585,447			11,128,343	(542,399)	(3,048,405)
Beginning 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)
Total comprehensive income	501,633											526,091	(24,458)
Preferred stock cash dividends	(18,130)											(18,130)
Exercise of stock warrants into common stock											$ (2,117)				$ 2,117
Purchases of treasury stock	(498,500)													(498,500)
Stock-based compensation plans:
Compensation expense, net	9,702						(1)		9,030					673
Exercises of stock options, net	6,122								(880)					7,002
Directors’ stock plan	604								19					585
Deferred compensation plans, net, including dividend equivalents								25				(25)
Common stock cash dividends	(143,231)											(143,231)
Ending balance at Sep. 30, 2018	15,436,085			1,231,500			79,883	1,716	6,585,447			11,128,343	(542,399)	(3,048,405)
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	1,775,856											1,436,083	339,773
Preferred stock cash dividends	(55,404)											(55,404)
Redemption of Series A and Series C preferred stock		$ (381,500)			$ (381,500)
Issuance of Series G preferred stock			$ 396,000			$ 400,000				$ (4,000)
Purchases of treasury stock	(1,067,575)													(1,067,575)
Stock-based compensation plans:
Compensation expense, net	40,552						(12)		12,728					27,836
Stock purchase plan	11,832								(67)					11,899
Exercises of stock options, net	5,326								(2,953)					8,279
Directors’ stock plan	1,564								(105)					1,669
Deferred compensation plans, net, including dividend equivalents	(64)							(179)	(327)			(64)		506
Performance share unit dividends									87			(87)
Common stock cash dividends	(406,967)											(406,967)
Ending balance at Sep. 30, 2019	15,779,811			1,250,000			79,871	1,547	6,584,705			12,490,233	(80,308)	(4,546,237)
Beginning 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)
Total comprehensive income	512,731											480,081	32,650
Preferred stock cash dividends	(19,144)											(19,144)
Redemption of Series A and Series C preferred stock		$ (381,500)			$ (381,500)
Issuance of Series G preferred stock			$ 396,000			$ 400,000				$ (4,000)
Purchases of treasury stock	(299,963)													(299,963)
Stock-based compensation plans:
Compensation expense, net	11,697								11,197					500
Exercises of stock options, net	599								(135)					734
Directors’ stock plan	496								11					485
Deferred compensation plans, net, including dividend equivalents								21				(21)
Performance share unit dividends									29			(29)
Common stock cash dividends	(132,932)											(132,932)
Ending balance at Sep. 30, 2019	$ 15,779,811			$ 1,250,000			$ 79,871	$ 1,547	$ 6,584,705			$ 12,490,233	$ (80,308)	$ (4,546,237)