INTEREST REVENUE AND EXPENSE (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Interest revenue
Loan interest, including fees	$ 8,874	$ 9,421	$ 26,516	$ 30,820
Deposits with banks	147	116	418	802
Securities borrowed and purchased under agreements to resell	264	352	763	1,961
Investments, including dividends	1,885	1,870	5,455	6,248
Trading account assets	1,284	1,457	4,091	4,720
Other interest-bearing assets	196	98	404	491
Total interest revenue	12,650	13,314	37,647	45,042
Interest expense
Deposits	1,023	1,293	3,030	5,376
Securities loaned and sold under agreements to repurchase	287	292	800	1,830
Trading account liabilities	106	123	370	506
Short-term borrowings and other interest-bearing liabilities	8	88	70	612
Long-term debt	828	1,025	2,614	3,653
Total interest expense	2,252	2,821	6,884	11,977
Net interest revenue	10,398	10,493	30,763	33,065
Provision (benefit) for credit losses on loans	(188)	1,931	(2,793)	16,298
Net interest revenue after provision for credit losses on loans	10,586	8,562	33,556	16,767
Insurance fees and charges	$ 293	$ 375	$ 912	$ 870