LOANS - Types of Consumer Loan Modifications and Their Financial Effect (Details) - Consumer - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023
In North America offices
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.11%	0.21%
Total modifications balance	$ 335	$ 624
In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	276	501
In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	16	31
In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	30	70
In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	13	22
In North America offices | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0
In offices outside North America
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.38%	0.43%
Total modifications balance	$ 297	$ 335
In offices outside North America | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	16	31
In offices outside North America | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	2	4
In offices outside North America | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	4	10
In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	275	$ 290
Residential mortgages | In North America offices
Financing Receivable, Impaired [Line Items]
Trial modifications, period		3 months
Trial modifications, amount	15	$ 26
Loans that had gone through bankruptcy	$ 1	$ 2
Modifications as % of loans	0.05%	0.10%
Total modifications balance	$ 47	$ 100
Weighted average interest rate reduction %	1.00%	1.00%
Weighted average term extension	191 months	187 months
Weighted average delay in payments	6 months	6 months
Residential mortgages | In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 1	$ 1
Residential mortgages | In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	15	30
Residential mortgages | In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	29	64
Residential mortgages | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	2	5
Residential mortgages | In North America offices | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0
Residential mortgages | In offices outside North America
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	1.03%	1.09%
Total modifications balance	$ 278	$ 296
Weighted average interest rate reduction %	0.00%	0.00%
Weighted average term extension	1 month	2 months
Weighted average delay in payments	1 month	2 months
Payment deferral period		4 months
Residential mortgages | In offices outside North America | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 3	$ 5
Residential mortgages | In offices outside North America | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Residential mortgages | In offices outside North America | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Residential mortgages | In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	1
Residential mortgages | In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 275	$ 290
Home equity loans | In North America offices
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.23%	0.48%
Total modifications balance	$ 9	$ 19
Weighted average interest rate reduction %	2.00%	2.00%
Weighted average term extension	119 months	120 months
Weighted average delay in payments	6 months	6 months
Home equity loans | In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0
Home equity loans | In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Home equity loans | In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	1	6
Home equity loans | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	8	13
Home equity loans | In North America offices | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Credit cards
Financing Receivable, Impaired [Line Items]
Loans forgiven	$ 16	$ 26
Credit cards | In North America offices
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.18%	0.33%
Total modifications balance	$ 275	$ 499
Weighted average interest rate reduction %	22.00%	22.00%
Credit cards | In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 275	$ 499
Credit cards | In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Credit cards | In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Credit cards | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Credit cards | In North America offices | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 0
Credit cards | In offices outside North America
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.09%	0.17%
Total modifications balance	$ 12	$ 23
Weighted average interest rate reduction %	18.00%	18.00%
Credit cards | In offices outside North America | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 12	$ 23
Credit cards | In offices outside North America | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Credit cards | In offices outside North America | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Credit cards | In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Credit cards | In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Personal, small business and other
Financing Receivable, Impaired [Line Items]
Loans forgiven	$ 1	$ 1
Personal, small business and other | In North America offices
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.01%	0.02%
Total modifications balance	$ 4	$ 6
Weighted average interest rate reduction %	6.00%	6.00%
Weighted average term extension	13 months	14 months
Personal, small business and other | In North America offices | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 0	$ 1
Personal, small business and other | In North America offices | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	1	1
Personal, small business and other | In North America offices | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	0	0
Personal, small business and other | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	3	4
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
Personal, small business and other | In offices outside North America
Financing Receivable, Impaired [Line Items]
Modifications as % of loans	0.02%	0.04%
Total modifications balance	$ 7	$ 16
Weighted average interest rate reduction %	9.00%	8.00%
Weighted average term extension	20 months	21 months
Personal, small business and other | In offices outside North America | Interest rate reduction
Financing Receivable, Impaired [Line Items]
Total modifications balance	$ 1	$ 3
Personal, small business and other | In offices outside North America | Term extension
Financing Receivable, Impaired [Line Items]
Total modifications balance	2	4
Personal, small business and other | In offices outside North America | Payment delay
Financing Receivable, Impaired [Line Items]
Total modifications balance	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	4	9
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