FAIR VALUE MEASUREMENT - Estimate Fair Value of Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Assets
Loans	$ 8,040	$ 7,594
Liabilities
Deposits(5)	1,284,458	1,308,681
Total investments	476,657	519,085
Allowance for credit loss	18,574	18,145	$ 16,974	$ 16,455
Total loans	694,488	689,362
Corporate
Assets
Loans	7,759	7,281
Liabilities
Allowance for credit loss	2,556	2,714	$ 2,855	$ 2,415
Total loans	301,386	300,165
Carrying value
Assets
HTM debt securities, net of allowance	247,600	259,700
Securities borrowed and purchased under agreements to resell	133,200	139,600
Loans	667,600	663,300
Other financial assets	362,200	347,500
Liabilities
Deposits(5)	1,280,900	1,306,200
Securities loaned and sold under agreements to repurchase	205,600	215,600
Long-term debt	174,500	170,300
Other financial liabilities	137,700	132,800
Fair value
Assets
HTM debt securities, net of allowance	229,800	240,600
Securities borrowed and purchased under agreements to resell	133,200	139,700
Loans	673,500	673,200
Other financial assets	362,200	347,500
Liabilities
Deposits(5)	1,280,900	1,305,900
Securities loaned and sold under agreements to repurchase	205,600	215,600
Long-term debt	178,000	173,400
Other financial liabilities	137,700	132,800
Fair value | Non-marketable equity securities
Liabilities
Total investments	427	508
Fair value | Corporate
Liabilities
Total loans	7,759	7,281
Fair value | Level 1
Assets
HTM debt securities, net of allowance	120,200	124,000
Securities borrowed and purchased under agreements to resell	0	0
Loans	0	0
Other financial assets	260,600	243,100
Liabilities
Deposits(5)	0	0
Securities loaned and sold under agreements to repurchase	0	0
Long-term debt	0	0
Other financial liabilities	0	0
Fair value | Level 2
Assets
HTM debt securities, net of allowance	107,400	114,100
Securities borrowed and purchased under agreements to resell	133,200	139,700
Loans	0	0
Other financial assets	15,900	17,800
Liabilities
Deposits(5)	1,280,900	1,116,500
Securities loaned and sold under agreements to repurchase	205,600	215,600
Long-term debt	162,100	168,000
Other financial liabilities	34,700	29,200
Fair value | Level 3
Assets
HTM debt securities, net of allowance	2,200	2,500
Securities borrowed and purchased under agreements to resell	0	0
Loans	673,500	673,200
Other financial assets	85,700	86,600
Liabilities
Deposits(5)	0	189,400
Securities loaned and sold under agreements to repurchase	0	0
Long-term debt	15,900	5,400
Other financial liabilities	103,000	103,600
Fair value | Level 3 | Corporate
Fair value measurements additional disclosures
Unfunded lending commitments	13,500	14,200
Carried at cost | Non-marketable equity securities
Liabilities
Total investments	5,247	5,497
Lease financing
Liabilities
Total loans	300	300
Lease financing | Corporate
Liabilities
Total loans	$ 276	$ 275