Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Nonvoting Common Stock [Member]	Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Nonvoting Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock, at cost [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2019	$ 21,745		$ 2,793	$ 15	$ 0	$ 4,656	$ 19,960	$ (5,767)	$ 88
Beginning balance (shares) at Dec. 31, 2019				1,488	0
Increase (Decrease) in Stockholders' Equity
Net income	2,164						2,164
Other comprehensive income (loss), net of tax	5,598								5,598
Issuance of preferred stock, net	2,470		2,470
Dividends declared on preferred stock	(160)						(160)
Dividends declared on common stock	(700)						(700)
Stock option exercises and other	35					(13)		48
Share-based compensation	123					123
Other	56					31	(3)	28
Ending balance (shares) at Sep. 30, 2020				1,488	0
Ending balance at Sep. 30, 2020	31,331		5,263	$ 15	$ 0	4,797	21,261	(5,691)	5,686
Beginning balance at Jun. 30, 2020	30,815		5,263	$ 15	$ 0	4,760	20,876	(5,710)	5,611
Beginning balance (shares) at Jun. 30, 2020				1,488	0
Increase (Decrease) in Stockholders' Equity
Net income	698						698
Other comprehensive income (loss), net of tax	75								75
Dividends declared on preferred stock	(79)						(79)
Dividends declared on common stock	(234)						(234)
Stock option exercises and other	6					(3)		9
Share-based compensation	32					32
Other	18					8		10
Ending balance (shares) at Sep. 30, 2020				1,488	0
Ending balance at Sep. 30, 2020	31,331		5,263	$ 15	$ 0	4,797	21,261	(5,691)	5,686
Beginning balance at Dec. 31, 2020	56,060		7,733	$ 20	$ 1	26,515	21,975	(5,578)	5,394
Beginning balance (shares) at Dec. 31, 2020				1,995	79
Increase (Decrease) in Stockholders' Equity
Net income	4,275	$ 179					4,275
Other comprehensive income (loss), net of tax	(4,141)								(4,141)
Issuance of preferred stock, net	2,806		2,806
Redemption of preferred stock	(600)		(585)				(15)
Dividends declared on preferred stock	(331)						(331)
Dividends declared on common stock	(1,024)						(1,024)
Stock option exercises and other	162					(5)		167
Share-based compensation	188					188
Other	47					57		(10)
Ending balance (shares) at Sep. 30, 2021				1,995	79
Ending balance at Sep. 30, 2021	57,442		9,954	$ 20	$ 1	26,755	24,880	(5,421)	1,253
Beginning balance at Jun. 30, 2021	57,450		9,954	$ 20	$ 1	26,708	23,809	(5,450)	2,408
Beginning balance (shares) at Jun. 30, 2021				1,995	79
Increase (Decrease) in Stockholders' Equity
Net income	1,526	$ 64					1,526
Other comprehensive income (loss), net of tax	(1,155)								(1,155)
Dividends declared on preferred stock	(113)						(113)
Dividends declared on common stock	(342)						(342)
Stock option exercises and other	18					(13)		31
Share-based compensation	43					43
Other	15					17		(2)
Ending balance (shares) at Sep. 30, 2021				1,995	79
Ending balance at Sep. 30, 2021	$ 57,442		$ 9,954	$ 20	$ 1	$ 26,755	$ 24,880	$ (5,421)	$ 1,253