LOANS - Defaults of Modified Consumer Loans (Details) - Consumer - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	$ 12	$ 61
In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	12
In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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	0
In North America offices | Combination: Term extension and payment delay(5)
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	2	9
In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1
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
In offices outside North America | Combination: Term extension and payment delay(5)
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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	1
Residential mortgages | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	4
Residential mortgages | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
Residential mortgages | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
Residential mortgages | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Residential mortgages | In North America offices | Combination: Term extension and payment delay(5)
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Residential mortgages | In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	2	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
Residential mortgages | In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
Residential mortgages | In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1
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
Residential mortgages | In offices outside North America | Combination: Term extension and payment delay(5)
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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	1
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
Home equity loans | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
Home equity loans | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Home equity loans | In North America offices | Combination: Term extension and payment delay(5)
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Credit cards | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	12	57
Credit cards | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	12
Credit cards | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
Credit cards | In North America offices | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Credit cards | In North America offices | Combination: Term extension and payment delay(5)
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Credit cards | In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	4
Credit cards | In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
Credit cards | In offices outside North America | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0
Credit cards | In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Credit cards | In offices outside North America | Combination: Term extension and payment delay(5)
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Personal, small business and other | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	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
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
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
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	0
Personal, small business and other | In North America offices | Combination: Term extension and payment delay(5)
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
Personal, small business and other | In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0	$ 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
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
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
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	0
Personal, small business and other | In offices outside North America | Combination: Term extension and payment delay(5)
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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