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 new accounting standards	Cumulative effects from adoption of new accounting standards Retained Earnings	Cumulative effects from adoption of new accounting standards Accumulated Other Comprehensive Income (Loss)
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 (loss)		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 (loss)		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 (loss)		(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 (loss)		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)
Beginning balance (shares) at Dec. 31, 2020			4,975,000	679,932,837
Beginning balance at Dec. 31, 2020		60,204	$ 0	$ 7	33,480	40,088	3,494	(16,865)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)		1,614				3,325	(1,711)
Dividends, common stock (shares)	[1]			13,356
Dividends, common stock	[1]	(184)		$ 0	1	(185)
Dividends, preferred stock		(61)				(61)
Purchases of treasury stock		(575)						(575)
Issuances of common stock and restricted stock, net of forfeitures (shares)				2,531,966
Issuances of common stock and restricted stock, net of forfeitures		60		$ 0	60
Exercises of stock options (shares)				283,398
Exercises of stock options		19		$ 0	19
Compensation expense for restricted stock units and stock options		111			111
Ending balance (shares) at Mar. 31, 2021			4,975,000	682,761,557
Ending balance at Mar. 31, 2021		61,188	$ 0	$ 7	33,671	43,167	1,783	(17,440)
Beginning balance (shares) at Dec. 31, 2020			4,975,000	679,932,837
Beginning balance at Dec. 31, 2020		60,204	$ 0	$ 7	33,480	40,088	3,494	(16,865)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)		7,831
Redemptions of preferred stock (shares)			(1,000,000)
Redemptions of preferred stock		(1,000)	$ 0		(988)	(12)
Ending balance (shares) at Sep. 30, 2021			6,075,000	684,515,909
Ending balance at Sep. 30, 2021		63,544	$ 0	$ 7	35,051	48,944	1,360	(21,818)
Beginning balance (shares) at Mar. 31, 2021			4,975,000	682,761,557
Beginning balance at Mar. 31, 2021		61,188	$ 0	$ 7	33,671	43,167	1,783	(17,440)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)		3,545				3,536	9
Dividends, common stock (shares)	[1]			4,954
Dividends, common stock	[1]	(181)		$ 0	1	(182)
Dividends, preferred stock		(60)				(60)
Purchases of treasury stock		(1,668)						(1,668)
Issuances of common stock and restricted stock, net of forfeitures (shares)				583,779
Issuances of common stock and restricted stock, net of forfeitures		60		$ 0	60
Exercises of stock options (shares)				209,528
Exercises of stock options		15		$ 0	15
Issuances of preferred stock (shares)			1,675,000
Issuances of preferred stock		1,641	$ 0		1,641
Compensation expense for restricted stock units and stock options		84			84
Ending balance (shares) at Jun. 30, 2021			6,650,000	683,559,818
Ending balance at Jun. 30, 2021		64,624	$ 0	$ 7	35,472	46,461	1,792	(19,108)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)		2,672				3,104	(432)
Dividends, common stock (shares)	[1]			6,531
Dividends, common stock	[1]	(529)		$ 0	1	(530)
Dividends, preferred stock		(79)				(79)
Purchases of treasury stock		(2,710)						(2,710)
Issuances of common stock and restricted stock, net of forfeitures (shares)				531,629
Issuances of common stock and restricted stock, net of forfeitures		71		$ 0	71
Exercises of stock options (shares)				417,931
Exercises of stock options		20		$ 0	20
Issuances of preferred stock (shares)			425,000
Issuances of preferred stock		412	$ 0		412
Compensation expense for restricted stock units and stock options		63			63
Ending balance (shares) at Sep. 30, 2021			6,075,000	684,515,909
Ending balance at Sep. 30, 2021		$ 63,544	$ 0	$ 7	$ 35,051	$ 48,944	$ 1,360	$ (21,818)

[1] We declared dividends per share on our common stock of $1.20 and $0.10 in the third quarter of 2021 and 2020, respectively, and $2.00 and $0.90 in the first nine months of 2021 and 2020, respectively.