LOANS - Performance of Modified Consumer Loans (Details) - Consumer loans $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($)
In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	$ 931
Gross credit losses	118
In North America offices | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	606
In North America offices | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	164
In North America offices | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	161
In offices outside North America
Financing Receivable, Modified [Line Items]
Total modified loans balance	356
Gross credit losses	1
In offices outside North America | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	347
In offices outside North America | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	6
In offices outside North America | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	3
Residential mortgages | In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	145
Gross credit losses	0
Residential mortgages | In North America offices | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	62
Residential mortgages | In North America offices | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	19
Residential mortgages | In North America offices | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	64
Residential mortgages | In offices outside North America
Financing Receivable, Modified [Line Items]
Total modified loans balance	304
Gross credit losses	0
Residential mortgages | In offices outside North America | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	301
Residential mortgages | In offices outside North America | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	2
Residential mortgages | In offices outside North America | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	1
Home equity loans | In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	21
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	6
Credit cards | In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	756
Gross credit losses	118
Credit cards | In North America offices | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	522
Credit cards | In North America offices | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	143
Credit cards | In North America offices | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	91
Credit cards | In offices outside North America
Financing Receivable, Modified [Line Items]
Total modified loans balance	33
Gross credit losses	1
Credit cards | In offices outside North America | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	29
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	2
Personal, small business and other | In North America offices
Financing Receivable, Modified [Line Items]
Total modified loans balance	9
Gross credit losses	0
Personal, small business and other | In North America offices | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	8
Personal, small business and other | In North America offices | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	1
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	19
Gross credit losses	0
Personal, small business and other | In offices outside North America | Current
Financing Receivable, Modified [Line Items]
Total modified loans balance	17
Personal, small business and other | In offices outside North America | 30–89 days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	2
Personal, small business and other | In offices outside North America | 90+ days past due
Financing Receivable, Modified [Line Items]
Total modified loans balance	$ 0