INTEREST REVENUE AND EXPENSE (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Interest revenue
Loan interest, including fees	$ 8,733	$ 10,149	$ 17,642	$ 21,399
Deposits with banks	126	159	271	686
Securities borrowed and purchased under agreements to resell	205	401	499	1,609
Investments, including dividends	1,818	2,097	3,570	4,378
Trading account assets	1,470	1,673	2,807	3,263
Other interest-bearing assets	111	110	208	393
Total interest revenue	12,463	14,589	24,997	31,728
Interest expense
Deposits	955	1,469	2,007	4,083
Securities loaned and sold under agreements to repurchase	260	453	513	1,538
Trading account liabilities	150	144	264	383
Short-term borrowings and other interest-bearing liabilities	31	140	62	524
Long-term debt	868	1,303	1,786	2,628
Total interest expense	2,264	3,509	4,632	9,156
Net interest revenue	10,199	11,080	20,365	22,572
Provision (benefit) for credit losses on loans	(1,126)	7,990	(2,605)	14,367
Net interest revenue after provision for credit losses on loans	11,325	3,090	22,970	8,205
Insurance fees and charges	$ 279	$ 270	$ 619	$ 495