Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Preferred stock	Common stock	Additional paid-in capital	Retained earnings	Retained earnings Cumulative effect of change in accounting principles	Accumulated other comprehensive income	Accumulated other comprehensive income Cumulative effect of change in accounting principles	Shares held in RSU Trust, at cost	Treasury stock, at cost
Beginning balance at Dec. 31, 2017		$ 26,068	$ 4,105	$ 90,579	$ 177,676	$ (183)	$ (119)	$ 88	$ (21)	$ (42,595)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance		1,696
Redemption		(1,696)
Shares issued and commitments to issue common stock for employee share-based compensation awards, and related tax effects				(738)
Other				(679)
Net income	$ 32,474				32,474
Dividends declared:
Preferred stock					(1,551)
Common stock ($3.60, $3.40 and $2.72 per share for 2020, 2019 and 2018, respectively)					(9,214)
Other comprehensive income/(loss), after-tax	(1,476)						(1,476)
Liquidation of RSU Trust									0
Repurchase			(19,983)							(19,983)
Reissuance										2,084
Ending balance at Dec. 31, 2018	256,515	26,068	4,105	89,162	199,202	62	(1,507)		(21)	(60,494)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance		5,000
Redemption		(4,075)
Shares issued and commitments to issue common stock for employee share-based compensation awards, and related tax effects				(591)
Other				(49)
Net income	36,431				36,431
Dividends declared:
Preferred stock					(1,587)
Common stock ($3.60, $3.40 and $2.72 per share for 2020, 2019 and 2018, respectively)					(10,897)
Other comprehensive income/(loss), after-tax	3,076						3,076
Liquidation of RSU Trust									0
Repurchase			(24,121)							(24,121)
Reissuance										1,566
Ending balance at Dec. 31, 2019	261,330	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				(72)
Other				(56)
Net income	29,131				29,131
Dividends declared:
Preferred stock					(1,583)
Common stock ($3.60, $3.40 and $2.72 per share for 2020, 2019 and 2018, respectively)					(11,119)
Other comprehensive income/(loss), after-tax	6,417						6,417
Liquidation of RSU Trust									21
Repurchase			(6,397)							(6,397)
Reissuance										1,262
Ending balance at Dec. 31, 2020	$ 279,354	$ 30,063	$ 4,105	$ 88,394	$ 236,990		$ 7,986		$ 0	$ (88,184)