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, 2016	$ 16,486,622	$ 1,231,500	$ 79,973	$ 2,145	$ 6,676,948		$ 9,222,488	$ (294,636)	$ (431,796)
Total comprehensive income	1,132,624						1,085,903	46,721
Preferred stock cash dividends	(54,604)						(54,604)
Exercise of stock warrants into common stock						$ (22,992)				$ 22,992
Purchases of treasury stock	(981,691)								(981,691)
Stock-based compensation plans:
Compensation expense, net	6,016		(63)		(51,606)				57,685
Exercises of stock options, net	61,292				(6,722)				68,014
Stock purchase plan	10,831				2,563				8,268
Directors’ stock plan	1,426				225				1,201
Deferred compensation plans, net, including dividend equivalents	(157)			(318)	(368)		(65)		594
Common stock cash dividends	(344,307)						(344,307)
Ending balance at Sep. 30, 2017	16,318,052	1,231,500	79,910	1,827	6,598,048		9,909,415	(247,915)	(1,254,733)
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 principles- 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
Exercises of stock options, net	56,793				(3,282)				60,075
Stock purchase plan	11,124				2,358				8,766
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)