Consolidated Statement of Changes in Shareholders' Equity - 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, 2016	$ 16,486,622				$ 1,231,500			$ 79,973	$ 2,145	$ 6,676,948			$ 9,222,488	$ (294,636)	$ (431,796)
Total comprehensive income	1,403,157												1,408,306	(5,149)
Reclassification of income tax effects to retained earnings	64,029												64,029	(64,029)
Preferred stock cash dividends	(72,734)												(72,734)
Exercise of stock warrants into common stock												$ (28,746)				$ 28,746
Purchases of treasury stock	(1,205,905)														(1,205,905)
Stock-based compensation transactions, net	96,879							(64)	(298)	(57,347)			(85)		154,673
Common stock cash dividends	(457,200)												(457,200)
Ending 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 inaccounting principle — equity securities	(16,853)	[1]											16,853	(16,853)
Total comprehensive income	1,878,666												1,918,080	(39,414)
Preferred stock cash dividends	(72,521)												(72,521)
Exercise of stock warrants into common stock												$ (22,394)				$ 22,394
Purchases of treasury stock	(2,194,396)														(2,194,396)
Stock-based compensation transactions, net	108,081							(26)	(121)	10,881			(86)		97,433
Common stock cash dividends	(510,458)												(510,458)
Ending 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	2,142,550												1,929,149	213,401
Preferred stock cash dividends	(72,482)												(72,482)
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	(1,349,785)														(1,349,785)
Stock-based compensation transactions, net	73,891							(12)	(160)	18,197			(207)		56,073
Common stock cash dividends	(552,216)												(552,216)
Ending balance at Dec. 31, 2019	$ 15,716,649				$ 1,250,000			$ 79,871	$ 1,566	$ 6,593,539			$ 12,820,916	$ (206,680)	$ (4,822,563)

[1] Beginning January 1, 2018, equity securities with readily determinable market values are required to be measured at fair value with changes in fair value recognized in the income statement. Prior to that date, such changes in fair value were reflected in other comprehensive income. Separate presentation of investment securities with an other-than-temporary impairment change is no longer required.