LOANS - Defaults of Modified Consumer Loans (Details) - Consumer loans - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	$ 114	$ 103
In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	106	92
In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	4	8
In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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	4	3
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
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
In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	3	9
In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	5
In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0
In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	4
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
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
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
Residential mortgages | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	7	10
Residential mortgages | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0
Residential mortgages | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	4	8
Residential mortgages | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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	3	2
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
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
Residential mortgages | In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	4
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
Residential mortgages | In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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	4
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
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
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
Home equity loans | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Home equity loans | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
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
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
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
Total credit cards | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	106	92
Total credit cards | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	106	92
Total credit cards | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0
Total credit cards | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0
Total 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
Total 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
Total 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
Total credit cards | In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	5
Total credit cards | In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	5
Total credit cards | In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0
Total credit cards | In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	0
Total 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
Total 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
Total 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
Personal, small business and other | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	1
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
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
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
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	1
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
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
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
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
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
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
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
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
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