LOANS - Defaults of Modified Consumer Loans (Details) - Consumer loans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	$ 113	$ 67	$ 204	$ 100
In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	105	61	178	94
In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	6	5	22	5
In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	1	0	1
In North America offices | Combination: interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	2	0	4	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	2	7	7
In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	2	1	3
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	0	0	3	2
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	3	2
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	7	6	25	7
Residential mortgages | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0	0	1
Residential mortgages | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	6	5	22	5
Residential mortgages | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	1	0	1
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	1	0	3	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	0	0	3	2
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	0	0	3	2
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	105	61	178	93
Credit cards | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	105	61	178	93
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	1	2	1	3
Credit cards | In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	2	1	3
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	3	2
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	3	2
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