LOANS - Defaults of Modified Consumer Loans (Details) - Consumer loans - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	$ 105	$ 51	$ 156	$ 56
In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	95	51	136	56
In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	9	0	17	0
In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	0	3	0
In North America offices | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	2	1	4	2
In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	1	0	1
In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	0	2	0
In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	0	2	1
In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
In offices outside North America | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Residential mortgages | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	9	1	19	1
Residential mortgages | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	1	0	1
Residential mortgages | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	9	0	17	0
Residential mortgages | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Residential mortgages | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	2	0
Residential mortgages | In North America offices | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Residential mortgages | In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Residential mortgages | In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	0	2	0
Residential mortgages | In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Residential mortgages | In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Residential mortgages | In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	0	2	0
Residential mortgages | In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Residential mortgages | In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Residential mortgages | In offices outside North America | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Home equity loans | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Home equity loans | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Home equity loans | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Home equity loans | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Home equity loans | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Home equity loans | In North America offices | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Home equity loans | In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	95	50	136	55
Credit cards | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	95	50	136	55
Credit cards | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In North America offices | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	1	0	1
Credit cards | In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	1	0	1
Credit cards | In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Credit cards | In offices outside North America | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Personal, small business and other | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	0	1	0
Personal, small business and other | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Personal, small business and other | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Personal, small business and other | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Personal, small business and other | In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	0	1	0
Personal, small business and other | In North America offices | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Personal, small business and other | In North America offices | Combination: interest rate reduction, term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Personal, small business and other | In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	0	2	1
Personal, small business and other | In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Personal, small business and other | In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Personal, small business and other | In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	0
Personal, small business and other | In offices outside North America | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	0	2	1
Personal, small business and other | In offices outside North America | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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, Modified [Line Items]
Total loans defaulted within one year of modification	$ 0	$ 0	$ 0	$ 0