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 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				(660)
Other				(5)
Net income	$ 2,865				2,865
Dividends declared:
Preferred stock					(421)
Common stock ($0.90 and $0.90 per share)					(2,779)
Other comprehensive income/(loss), after-tax	5,849						5,849
Repurchase									(6,397)
Reissuance									1,060
Ending balance at Mar. 31, 2020	261,262	30,063	4,105	87,857	220,226		7,418	(21)	(88,386)
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		1,500
Redemption		0
Shares issued and commitments to issue common stock for employee share-based compensation awards, and related tax effects				(363)
Other				(26)
Net income	14,300				14,300
Dividends declared:
Preferred stock					(379)
Common stock ($0.90 and $0.90 per share)					(2,760)
Other comprehensive income/(loss), after-tax	(6,945)						(6,945)
Repurchase									(4,999)
Reissuance									1,032
Ending balance at Mar. 31, 2021	$ 280,714	$ 31,563	$ 4,105	$ 88,005	$ 248,151		$ 1,041	$ 0	$ (92,151)