Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands		Total	Series I Preferred Stock [Member]	ASU 2016-13 [Member]	Preferred Stock [Member]	Preferred Stock [Member] Series I Preferred Stock [Member]	Common Stock [Member]	Common Stock Issuable [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series I Preferred Stock [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, 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)
Beginning balance at Dec. 31, 2020		16,187,283			1,250,000		79,871	1,344	6,617,404		13,444,428		(63,032)	(5,142,732)
Total comprehensive income		1,253,391									1,400,778		(147,387)
Preferred stock cash dividends	[1]	(51,150)									(51,150)
Issuance of Series I preferred stock			$ 495,000			$ 500,000				$ (5,000)
Stock-based compensation transactions, net		71,774						(148)	12,252		(616)			60,286
Common stock cash dividends		(427,527)									(427,527)
Ending balance at Sep. 30, 2021		17,528,771			1,750,000		79,871	1,196	6,624,656		14,365,913		(210,419)	(5,082,446)
Beginning balance at Jun. 30, 2021		16,720,304			1,250,000		79,871	1,179	6,620,528		14,030,215		(176,974)	(5,084,515)
Total comprehensive income		462,015									495,460		(33,445)
Preferred stock cash dividends	[1]	(17,050)									(17,050)
Issuance of Series I preferred stock			$ 495,000			$ 500,000				$ (5,000)
Stock-based compensation transactions, net		11,007						17	9,128		(207)			2,069
Common stock cash dividends		(142,505)									(142,505)
Ending balance at Sep. 30, 2021		$ 17,528,771			$ 1,750,000		$ 79,871	$ 1,196	$ 6,624,656		$ 14,365,913		$ (210,419)	$ (5,082,446)

[1] For the three-month and nine-month periods ended September 30, 2021, 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 $375.00, respectively.  Dividends per preferred share for the three-month and nine-month periods ended September 30, 2020 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.