LOANS - Types of Consumer Loan Modifications and Their Financial Effect (Details) - Consumer loans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
In North America offices
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.16%	0.16%	0.49%	0.39%
Total modifications balance	$ 510	$ 507	$ 1,579	$ 1,219
In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	467	472	1,197	1,124
In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	15	13	39	47
In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	14	11	303	24
In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	14	11	40	24
In North America offices | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0	$ 0	$ 0
In offices outside North America
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.04%	0.04%	0.10%	0.10%
Total modifications balance	$ 31	$ 27	$ 79	$ 76
In offices outside North America | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	11	8	26	18
In offices outside North America | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	1	0	4
In offices outside North America | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	8	13	27	39
In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	12	5	26	15
In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
In offices outside North America | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Residential mortgages
Financing Receivable, Impaired [Line Items]
Loans forgiven	1	1	$ 1	2
Residential mortgages | In North America offices
Financing Receivable, Impaired [Line Items]
Trial modifications, period			3 months
Trial modifications, amount	40	8	$ 59	22
Loans that had gone through bankruptcy	$ 4	$ 2	$ 8	$ 5
Modifications as % of loans	0.03%	0.03%	0.30%	0.07%
Total modifications balance	$ 35	$ 29	$ 355	$ 77
Weighted-average interest rate reduction %	0.00%	1.00%	0.00%	1.00%
Weighted average term extension	113 months	145 months	139 months	171 months
Weighted average delay in payments	10 months	10 months	9 months	9 months
Residential mortgages | In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 1	$ 1	$ 1
Residential mortgages | In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	15	13	39	47
Residential mortgages | In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	14	11	299	22
Residential mortgages | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	6	4	16	7
Residential mortgages | In North America offices | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Residential mortgages | In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0	$ 0	$ 0
Residential mortgages | In offices outside North America
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.04%	0.05%	0.13%	0.16%
Total modifications balance	$ 10	$ 13	$ 31	$ 41
Weighted-average interest rate reduction %	1.00%	0.00%	2.00%	2.00%
Weighted average term extension	171 months		183 months	188 months
Weighted average delay in payments	12 months	12 months	12 months	12 months
Residential mortgages | In offices outside North America | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0	$ 0	$ 0
Residential mortgages | In offices outside North America | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Residential mortgages | In offices outside North America | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	8	13	27	39
Residential mortgages | In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	2	0	4	2
Residential mortgages | In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Residential mortgages | In offices outside North America | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0	$ 0	$ 0
Home equity loans | In North America offices
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.00%	0.00%	0.10%	0.06%
Total modifications balance	$ 0	$ 0	$ 3	$ 2
Weighted-average interest rate reduction %	0.00%	0.00%	0.00%	1.00%
Weighted average term extension				151 months
Weighted average delay in payments			8 months	9 months
Home equity loans | In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0	$ 0	$ 0
Home equity loans | In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Home equity loans | In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	3	1
Home equity loans | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	1
Home equity loans | In North America offices | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Home equity loans | In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	0	0	0
Home equity loans | In offices outside North America
Financing Receivable, Impaired [Line Items]
Weighted average term extension	21 months
Credit cards
Financing Receivable, Impaired [Line Items]
Loans forgiven	$ 38	$ 30	$ 93	$ 58
Credit cards | In North America offices
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.28%	0.29%	0.71%	0.69%
Total modifications balance	$ 467	$ 471	$ 1,196	$ 1,122
Weighted-average interest rate reduction %	24.00%	25.00%	25.00%	24.00%
Weighted average delay in payments			4 months
Credit cards | In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 467	$ 471	$ 1,195	$ 1,122
Credit cards | In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Credit cards | In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	1	0
Credit cards | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Credit cards | In North America offices | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Credit cards | In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0	$ 0	$ 0
Credit cards | In offices outside North America
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.06%	0.05%	0.15%	0.11%
Total modifications balance	$ 8	$ 6	$ 20	$ 14
Weighted-average interest rate reduction %	26.00%	24.00%	24.00%	24.00%
Weighted average term extension			21 months
Credit cards | In offices outside North America | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 7	$ 6	$ 19	$ 14
Credit cards | In offices outside North America | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Credit cards | In offices outside North America | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Credit cards | In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	1	0	1	0
Credit cards | In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Credit cards | In offices outside North America | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Personal, small business and other
Financing Receivable, Impaired [Line Items]
Loans forgiven	$ 3	$ 1	$ 3	$ 2
Personal, small business and other | In North America offices
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.02%	0.02%	0.08%	0.05%
Total modifications balance	$ 8	$ 7	$ 25	$ 18
Weighted-average interest rate reduction %	8.00%	8.00%	8.00%	8.00%
Weighted average term extension	19 months	19 months	19 months	18 months
Weighted average delay in payments				7 months
Personal, small business and other | In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0	$ 1	$ 1
Personal, small business and other | In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Personal, small business and other | In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	1
Personal, small business and other | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	8	7	24	16
Personal, small business and other | In North America offices | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Personal, small business and other | In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0	$ 0	$ 0
Personal, small business and other | In offices outside North America
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.03%	0.02%	0.07%	0.06%
Total modifications balance	$ 13	$ 8	$ 28	$ 21
Weighted-average interest rate reduction %	7.00%	7.00%	6.00%	7.00%
Weighted average term extension	21 months	25 months	25 months	24 months
Personal, small business and other | In offices outside North America | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 4	$ 2	$ 7	$ 4
Personal, small business and other | In offices outside North America | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	1	0	4
Personal, small business and other | In offices outside North America | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Personal, small business and other | In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	9	5	21	13
Personal, small business and other | In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0	0	0
Personal, small business and other | In offices outside North America | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0	$ 0	$ 0