LOANS - Types of Consumer Loan Modifications and Their Financial Effect (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Financing receivable impaired
Loans, net of unearned income	$ 689,362	$ 657,221
Consumer
Financing receivable impaired
Loans, net of unearned income	$ 389,197	368,067
Consumer | In North America offices
Financing receivable impaired
Modifications as % of loans	0.40%
Total modifications balance	$ 1,238
Consumer | In North America offices | Interest rate reduction
Financing receivable impaired
Total modifications balance	1,044
Consumer | In North America offices | Term extension
Financing receivable impaired
Total modifications balance	63
Consumer | In North America offices | Payment delay
Financing receivable impaired
Total modifications balance	98
Consumer | In North America offices | Combination: interest rate reduction and term extension
Financing receivable impaired
Total modifications balance	33
Consumer | In North America offices | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	$ 0
Consumer | Outside U.S.
Financing receivable impaired
Modifications as % of loans	0.53%
Total modifications balance	$ 404
Consumer | Outside U.S. | Interest rate reduction
Financing receivable impaired
Total modifications balance	47
Consumer | Outside U.S. | Term extension
Financing receivable impaired
Total modifications balance	7
Consumer | Outside U.S. | Payment delay
Financing receivable impaired
Total modifications balance	33
Consumer | Outside U.S. | Combination: interest rate reduction and term extension
Financing receivable impaired
Total modifications balance	18
Consumer | Outside U.S. | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	299
Consumer | Residential first mortgages
Financing receivable impaired
Loans, net of unearned income	$ 108,711	96,039
Consumer | Residential first mortgages | In North America offices
Financing receivable impaired
Modifications as % of loans	0.15%
Total modifications balance	$ 164
Weighted- average interest rate reduction %	1.00%
Weighted- average term extension (months)	202 months
Weighted- average delay in payments (months)	9 months
Consumer | Residential first mortgages | In North America offices | Interest rate reduction
Financing receivable impaired
Total modifications balance	$ 3
Consumer | Residential first mortgages | In North America offices | Term extension
Financing receivable impaired
Total modifications balance	63
Consumer | Residential first mortgages | In North America offices | Payment delay
Financing receivable impaired
Total modifications balance	89
Consumer | Residential first mortgages | In North America offices | Combination: interest rate reduction and term extension
Financing receivable impaired
Total modifications balance	9
Consumer | Residential first mortgages | In North America offices | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	$ 0
Consumer | Residential first mortgages | Outside U.S.
Financing receivable impaired
Modifications as % of loans	1.26%
Total modifications balance	$ 334
Weighted- average interest rate reduction %	2.00%
Weighted- average term extension (months)	4 months
Weighted- average delay in payments (months)	4 months
Consumer | Residential first mortgages | Outside U.S. | Interest rate reduction
Financing receivable impaired
Total modifications balance	$ 0
Consumer | Residential first mortgages | Outside U.S. | Term extension
Financing receivable impaired
Total modifications balance	0
Consumer | Residential first mortgages | Outside U.S. | Payment delay
Financing receivable impaired
Total modifications balance	33
Consumer | Residential first mortgages | Outside U.S. | Combination: interest rate reduction and term extension
Financing receivable impaired
Total modifications balance	2
Consumer | Residential first mortgages | Outside U.S. | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	299
Consumer | Home equity loans
Financing receivable impaired
Loans, net of unearned income	$ 3,592	4,580
Consumer | Home equity loans | In North America offices
Financing receivable impaired
Modifications as % of loans	0.58%
Total modifications balance	$ 21
Weighted- average interest rate reduction %	2.00%
Weighted- average term extension (months)	121 months
Weighted- average delay in payments (months)	9 months
Consumer | Home equity loans | In North America offices | Interest rate reduction
Financing receivable impaired
Total modifications balance	$ 0
Consumer | Home equity loans | In North America offices | Term extension
Financing receivable impaired
Total modifications balance	0
Consumer | Home equity loans | In North America offices | Payment delay
Financing receivable impaired
Total modifications balance	9
Consumer | Home equity loans | In North America offices | Combination: interest rate reduction and term extension
Financing receivable impaired
Total modifications balance	12
Consumer | Home equity loans | In North America offices | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	0
Consumer | Credit cards
Financing receivable impaired
Loans, net of unearned income	164,110	150,098
Loans forgiven	$ 50
Consumer | Credit cards | In North America offices
Financing receivable impaired
Modifications as % of loans	0.63%
Total modifications balance	$ 1,039
Weighted- average interest rate reduction %	23.00%
Consumer | Credit cards | In North America offices | Interest rate reduction
Financing receivable impaired
Total modifications balance	$ 1,039
Consumer | Credit cards | In North America offices | Term extension
Financing receivable impaired
Total modifications balance	0
Consumer | Credit cards | In North America offices | Payment delay
Financing receivable impaired
Total modifications balance	0
Consumer | Credit cards | In North America offices | Combination: interest rate reduction and term extension
Financing receivable impaired
Total modifications balance	0
Consumer | Credit cards | In North America offices | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	$ 0
Consumer | Credit cards | Outside U.S.
Financing receivable impaired
Modifications as % of loans	0.30%
Total modifications balance	$ 43
Weighted- average interest rate reduction %	18.00%
Weighted- average term extension (months)	37 months
Consumer | Credit cards | Outside U.S. | Interest rate reduction
Financing receivable impaired
Total modifications balance	$ 42
Consumer | Credit cards | Outside U.S. | Term extension
Financing receivable impaired
Total modifications balance	0
Consumer | Credit cards | Outside U.S. | Payment delay
Financing receivable impaired
Total modifications balance	0
Consumer | Credit cards | Outside U.S. | Combination: interest rate reduction and term extension
Financing receivable impaired
Total modifications balance	1
Consumer | Credit cards | Outside U.S. | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	0
Consumer | Personal, small business and other
Financing receivable impaired
Loans, net of unearned income	35,258	$ 36,812
Loans forgiven	$ 2
Consumer | Personal, small business and other | In North America offices
Financing receivable impaired
Modifications as % of loans	0.04%
Total modifications balance	$ 14
Weighted- average interest rate reduction %	6.00%
Weighted- average term extension (months)	15 months
Consumer | Personal, small business and other | In North America offices | Interest rate reduction
Financing receivable impaired
Total modifications balance	$ 2
Consumer | Personal, small business and other | In North America offices | Term extension
Financing receivable impaired
Total modifications balance	0
Consumer | Personal, small business and other | In North America offices | Payment delay
Financing receivable impaired
Total modifications balance	0
Consumer | Personal, small business and other | In North America offices | Combination: interest rate reduction and term extension
Financing receivable impaired
Total modifications balance	12
Consumer | Personal, small business and other | In North America offices | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	$ 0
Consumer | Personal, small business and other | Outside U.S.
Financing receivable impaired
Modifications as % of loans	0.08%
Total modifications balance	$ 27
Weighted- average interest rate reduction %	7.00%
Weighted- average term extension (months)	19 months
Consumer | Personal, small business and other | Outside U.S. | Interest rate reduction
Financing receivable impaired
Total modifications balance	$ 5
Consumer | Personal, small business and other | Outside U.S. | Term extension
Financing receivable impaired
Total modifications balance	7
Consumer | Personal, small business and other | Outside U.S. | Payment delay
Financing receivable impaired
Total modifications balance	0
Consumer | Personal, small business and other | Outside U.S. | Combination: interest rate reduction and term extension
Financing receivable impaired
Total modifications balance	15
Consumer | Personal, small business and other | Outside U.S. | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	$ 0