CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Millions		Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Cumulative effects from adoption of the CECL standard	Cumulative effects from adoption of the CECL standard Retained Earnings	Cumulative effects from adoption of the CECL standard Accumulated Other Comprehensive Income (Loss)
Beginning balance (shares) at Dec. 31, 2018			4,475,000	667,969,069
Beginning balance at Dec. 31, 2018		$ 51,668	$ 0	$ 7	$ 32,040	$ 35,875	$ (1,263)	$ (14,991)	$ (11)	$ (11)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		2,015				1,412	603
Dividends, common stock (shares)	[1]			32,700
Dividends, common stock	[1]	(191)		$ 0	3	(194)
Dividends, preferred stock		(52)				(52)
Purchases of treasury stock		(65)						(65)
Issuances of common stock and restricted stock, net of forfeitures (shares)				2,641,635
Issuances of common stock and restricted stock, net of forfeitures		52		$ 0	52
Exercises of stock options (shares)				5,000
Exercises of stock options		0		$ 0	0
Compensation expense for restricted stock units and stock options		65			65
Ending balance (shares) at Mar. 31, 2019			4,475,000	670,648,404
Ending balance at Mar. 31, 2019		53,481	$ 0	$ 7	32,160	37,030	(660)	(15,056)
Beginning balance (shares) at Dec. 31, 2018			4,475,000	667,969,069
Beginning balance at Dec. 31, 2018		51,668	$ 0	$ 7	32,040	35,875	(1,263)	(14,991)	(11)	(11)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		6,086
Ending balance (shares) at Sep. 30, 2019			5,975,000	672,084,002
Ending balance at Sep. 30, 2019		58,235	$ 0	$ 7	33,826	39,476	453	(15,527)
Beginning balance (shares) at Mar. 31, 2019			4,475,000	670,648,404
Beginning balance at Mar. 31, 2019		53,481	$ 0	$ 7	32,160	37,030	(660)	(15,056)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		2,455				1,625	830
Dividends, common stock (shares)	[1]			8,680
Dividends, common stock	[1]	(188)		$ 0	1	(189)
Dividends, preferred stock		(80)				(80)
Purchases of treasury stock		(2)						(2)
Issuances of common stock and restricted stock, net of forfeitures (shares)				745,017
Issuances of common stock and restricted stock, net of forfeitures		46		$ 0	46
Exercises of stock options (shares)				4,000
Exercises of stock options		0		$ 0	0
Compensation expense for restricted stock units and stock options		55			55
Ending balance (shares) at Jun. 30, 2019			4,475,000	671,406,101
Ending balance at Jun. 30, 2019		55,767	$ 0	$ 7	32,262	38,386	170	(15,058)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		1,616				1,333	283
Dividends, common stock (shares)	[1]			4,646
Dividends, common stock	[1]	(190)		$ 0	0	(190)
Dividends, preferred stock		(53)				(53)
Purchases of treasury stock		(469)						(469)
Issuances of common stock and restricted stock, net of forfeitures (shares)				673,255
Issuances of common stock and restricted stock, net of forfeitures		55		$ 0	55
Exercises of stock options (shares)				0
Exercises of stock options		0		$ 0	0
Issuances of preferred stock (shares)			1,500,000
Issuances of preferred stock		1,463	$ 0		1,463
Compensation expense for restricted stock units and stock options		46			46
Ending balance (shares) at Sep. 30, 2019			5,975,000	672,084,002
Ending balance at Sep. 30, 2019		58,235	$ 0	$ 7	33,826	39,476	453	(15,527)
Beginning balance (shares) at Dec. 31, 2019			4,975,000	672,969,391
Beginning balance at Dec. 31, 2019		58,011	$ 0	$ 7	32,980	40,340	1,156	(16,472)	(2,192)	(2,184)	$ (8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		1,191				(1,340)	2,531
Dividends, common stock (shares)	[1]			23,213
Dividends, common stock	[1]	(185)		$ 0	2	(187)
Dividends, preferred stock		(55)				(55)
Purchases of treasury stock		(386)						(386)
Issuances of common stock and restricted stock, net of forfeitures (shares)				2,618,628
Issuances of common stock and restricted stock, net of forfeitures		63		$ 0	63
Exercises of stock options (shares)				559,333
Exercises of stock options		20		$ 0	20
Issuances of preferred stock (shares)			1,250,000
Issuances of preferred stock		1,209	$ 0		1,209
Redemptions of preferred stock (shares)			(875,000)
Redemptions of preferred stock		(875)	$ 0		(853)	(22)
Compensation expense for restricted stock units and stock options		29			29
Ending balance (shares) at Mar. 31, 2020			5,350,000	676,170,565
Ending balance at Mar. 31, 2020		56,830	$ 0	$ 7	33,450	36,552	3,679	(16,858)
Beginning balance (shares) at Dec. 31, 2019			4,975,000	672,969,391
Beginning balance at Dec. 31, 2019		58,011	$ 0	$ 7	32,980	40,340	1,156	(16,472)	$ (2,192)	$ (2,184)	$ (8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		2,833
Ending balance (shares) at Sep. 30, 2020			5,475,000	678,318,329
Ending balance at Sep. 30, 2020		58,424	$ 0	$ 7	33,793	37,653	3,833	(16,862)
Beginning balance (shares) at Mar. 31, 2020			5,350,000	676,170,565
Beginning balance at Mar. 31, 2020		56,830	$ 0	$ 7	33,450	36,552	3,679	(16,858)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		(616)				(918)	302
Dividends, common stock (shares)	[1]			6,521
Dividends, common stock	[1]	(183)		$ 0	0	(183)
Dividends, preferred stock		(90)				(90)
Purchases of treasury stock		(2)						(2)
Issuances of common stock and restricted stock, net of forfeitures (shares)				1,041,311
Issuances of common stock and restricted stock, net of forfeitures		58		$ 0	58
Exercises of stock options (shares)				8,410
Exercises of stock options		0		$ 0	0
Compensation expense for restricted stock units and stock options		48			48
Ending balance (shares) at Jun. 30, 2020			5,350,000	677,226,807
Ending balance at Jun. 30, 2020		56,045	$ 0	$ 7	33,556	35,361	3,981	(16,860)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		2,258				2,406	(148)
Dividends, common stock (shares)	[1]			1,608
Dividends, common stock	[1]	(47)		$ 0	0	(47)
Dividends, preferred stock		(67)				(67)
Purchases of treasury stock		(2)						(2)
Issuances of common stock and restricted stock, net of forfeitures (shares)				1,073,323
Issuances of common stock and restricted stock, net of forfeitures		63		$ 0	63
Exercises of stock options (shares)				16,591
Exercises of stock options		1		$ 0	1
Issuances of preferred stock (shares)			125,000
Issuances of preferred stock		121	$ 0		121
Compensation expense for restricted stock units and stock options		52			52
Ending balance (shares) at Sep. 30, 2020			5,475,000	678,318,329
Ending balance at Sep. 30, 2020		$ 58,424	$ 0	$ 7	$ 33,793	$ 37,653	$ 3,833	$ (16,862)

[1] We declared dividend per share on our common stock of $0.10 and $0.40 in the third quarter of 2020 and 2019, respectively, and $0.90 and $1.20 in the first nine months of 2020 and 2019, respectively.