LOANS - Performance of Modified Consumer Loans (Details) - Consumer $ in Millions	6 Months Ended
	Jun. 30, 2023 USD ($)
In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	$ 624
Gross credit losses	57
In North America offices | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	375
In North America offices | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	123
In North America offices | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	126
In offices outside North America
Financing Receivable, Modified [Line Items]
Total modified loans balance	335
Gross credit losses	1
In offices outside North America | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	329
In offices outside North America | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	4
In offices outside North America | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	2
Residential mortgages | In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	100
Gross credit losses	0
Residential mortgages | In North America offices | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	36
Residential mortgages | In North America offices | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	20
Residential mortgages | In North America offices | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	44
Residential mortgages | In offices outside North America
Financing Receivable, Modified [Line Items]
Total modified loans balance	296
Gross credit losses	0
Residential mortgages | In offices outside North America | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	295
Residential mortgages | In offices outside North America | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	1
Residential mortgages | In offices outside North America | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	0
Home equity loans | In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	19
Gross credit losses	0
Home equity loans | In North America offices | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	14
Home equity loans | In North America offices | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	1
Home equity loans | In North America offices | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	4
Credit cards | In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	499
Gross credit losses	57
Credit cards | In North America offices | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	319
Credit cards | In North America offices | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	102
Credit cards | In North America offices | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	78
Credit cards | In offices outside North America
Financing Receivable, Modified [Line Items]
Total modified loans balance	23
Gross credit losses	0
Credit cards | In offices outside North America | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	20
Credit cards | In offices outside North America | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	2
Credit cards | In offices outside North America | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	1
Personal, small business and other | In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	6
Gross credit losses	0
Personal, small business and other | In North America offices | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	6
Personal, small business and other | In North America offices | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	0
Personal, small business and other | In North America offices | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	0
Personal, small business and other | In offices outside North America
Financing Receivable, Modified [Line Items]
Total modified loans balance	16
Gross credit losses	1
Personal, small business and other | In offices outside North America | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	14
Personal, small business and other | In offices outside North America | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	1
Personal, small business and other | In offices outside North America | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	$ 1