LOANS - Defaults of Modified Consumer Loans (Details) - Consumer - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	$ 51	$ 74	$ 56	$ 135
In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	51		56
In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0		0
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	0		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
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	1	7	2	16
In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1		1
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	0		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	0		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
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	1	13	1	17
Residential mortgages | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1		1
Residential mortgages | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	0		0
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	0		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
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	0	3	0	7
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	0		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
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	2	0	2
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
Credit cards | In North America offices
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	50	59	55	116
Credit cards | In North America offices | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	50		55
Credit cards | In North America offices | Term extension
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
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
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
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
Credit cards | In offices outside North America
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1	3	1	7
Credit cards | In offices outside North America | Interest rate reduction
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	1		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
Credit cards | In offices outside North America | Payment delay
Financing Receivable, Modified [Line Items]
Total loans defaulted within one year of modification	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
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
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	0	0	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		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	0		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
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	0	$ 1	1	$ 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
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	0		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
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