Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Preferred stock	Common stock	Additional paid-in capital	Retained earnings	Retained earnings Cumulative effect of a change in accounting principle	Accumulated other comprehensive income/(loss)	Shares held in Restricted Stock Units ("RSU") Trust, at cost	Treasury stock, at cost
Beginning balance at Dec. 31, 2019		$ 26,993	$ 4,105	$ 88,522	$ 223,211	$ (2,650)	$ 1,569	$ (21)	$ (83,049)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance		4,500
Redemption		(1,430)
Shares issued and commitments to issue common stock for employee share-based compensation awards, and related tax effects				(177)
Other				(56)
Net income	$ 16,995				16,995
Dividends declared:
Preferred stock					(1,203)
Common stock ($1.00 and $0.90 per share and $2.80 and $2.70 per share, respectively)					(8,339)
Other comprehensive income/(loss), after-tax	7,371						7,371
Liquidation of RSU Trust								10
Repurchase									(6,397)
Reissuance									1,159
Ending balance at Sep. 30, 2020	271,113	30,063	4,105	88,289	228,014		8,940	(11)	(88,287)
Beginning balance at Jun. 30, 2020		30,063	4,105	88,125	221,732		8,789	(11)	(88,337)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance		0
Redemption		0
Shares issued and commitments to issue common stock for employee share-based compensation awards, and related tax effects				215
Other				(51)
Net income	9,443				9,443
Dividends declared:
Preferred stock					(381)
Common stock ($1.00 and $0.90 per share and $2.80 and $2.70 per share, respectively)					(2,780)
Other comprehensive income/(loss), after-tax	151						151
Liquidation of RSU Trust								0
Repurchase									0
Reissuance									50
Ending balance at Sep. 30, 2020	271,113	30,063	4,105	88,289	228,014		8,940	(11)	(88,287)
Beginning balance at Dec. 31, 2020	279,354	30,063	4,105	88,394	236,990		7,986	0	(88,184)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance		7,350
Redemption		(2,575)
Shares issued and commitments to issue common stock for employee share-based compensation awards, and related tax effects				93
Other				(130)
Net income	37,935				37,935
Dividends declared:
Preferred stock					(1,174)
Common stock ($1.00 and $0.90 per share and $2.80 and $2.70 per share, respectively)					(8,475)
Other comprehensive income/(loss), after-tax	(7,023)						(7,023)
Liquidation of RSU Trust								0
Repurchase									(16,440)
Reissuance									1,126
Ending balance at Sep. 30, 2021	290,041	34,838	4,105	88,357	265,276		963	0	(103,498)
Beginning balance at Jun. 30, 2021		32,838	4,105	88,194	256,983		2,570	0	(98,304)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance		2,000
Redemption		0
Shares issued and commitments to issue common stock for employee share-based compensation awards, and related tax effects				227
Other				(64)
Net income	11,687				11,687
Dividends declared:
Preferred stock					(402)
Common stock ($1.00 and $0.90 per share and $2.80 and $2.70 per share, respectively)					(2,992)
Other comprehensive income/(loss), after-tax	(1,607)						(1,607)
Liquidation of RSU Trust								0
Repurchase									(5,240)
Reissuance									46
Ending balance at Sep. 30, 2021	$ 290,041	$ 34,838	$ 4,105	$ 88,357	$ 265,276		$ 963	$ 0	$ (103,498)