Consolidated Statement of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands		Total	ASU 2016-13 [Member]	Preferred Stock [Member]	Common Stock [Member]	Common Stock Issuable [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] ASU 2016-13 [Member]	Accumulated Other Comprehensive Income (Loss), Net [Member]	Treasury Stock [Member]
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	[1]	(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 transactions, net		59,210			(12)	(179)	9,363	(151)			50,189
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	[1]	(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 transactions, net		12,792				21	11,102	(50)			1,719
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)
Beginning 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)
Adoption of new accounting standard for credit losses			$ (91,925)						$ (91,925)
Total comprehensive income		1,264,195						882,012		382,183
Preferred stock cash dividends	[1]	(51,178)						(51,178)
Purchases of treasury stock		(373,750)									(373,750)
Stock-based compensation transactions, net		64,163				(239)	16,034	(310)			48,678
Common stock cash dividends		(427,141)						(427,141)
Ending balance at Sep. 30, 2020		16,101,013		1,250,000	79,871	1,327	6,609,573	13,132,374		175,503	(5,147,635)
Beginning balance at Jun. 30, 2020		15,945,105		1,250,000	79,871	1,308	6,599,069	12,919,345		244,630	(5,149,118)
Total comprehensive income		303,009						372,136		(69,127)
Preferred stock cash dividends	[1]	(17,050)						(17,050)
Stock-based compensation transactions, net		11,902				19	10,504	(104)			1,483
Common stock cash dividends		(141,953)						(141,953)
Ending balance at Sep. 30, 2020		$ 16,101,013		$ 1,250,000	$ 79,871	$ 1,327	$ 6,609,573	$ 13,132,374		$ 175,503	$ (5,147,635)

[1] For the three-month and nine-month periods ended September 30, 2020, dividends per preferred share were: Preferred Series E - $16.125 and $48.375, respectively; Preferred Series F - $128.125 and $384.375, respectively; and Preferred Series G - $125.00 and $375.694, respectively.  Dividends per preferred share for the three-month and nine-month periods ended September 30, 2019 were:  Preferred Series A - $15.9375 and $47.8125, respectively; Preferred Series C - $15.9375 and $47.8125, respectively; Preferred Series E - $16.125 and $48.375, respectively; and Preferred Series F - $128.125 and $384.375, respectively.