LOANS - Consumer Loans Troubled Debt Restructurings (Details) - Consumer loans $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2022 USD ($) loan	Sep. 30, 2022 USD ($) loan
In North America offices
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	46,810	125,453
Post-modification recorded investment	$ 278.0	$ 763.0
In North America offices | Residential mortgages
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	235	860
Post-modification recorded investment	$ 58.0	$ 195.0
Average interest rate reduction	0.00%	0.00%
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 1.8	$ 3.7
In North America offices | Residential mortgages | New OCC guidance
Financing Receivable, Modified [Line Items]
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 1.8	$ 3.7
In North America offices | Home equity loans
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	117	324
Post-modification recorded investment	$ 14.0	$ 30.0
Average interest rate reduction	0.00%	0.00%
In North America offices | Credit cards
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	46,326	123,886
Post-modification recorded investment	$ 203.0	$ 533.0
Average interest rate reduction	18.00%	18.00%
In North America offices | Personal, small business and other
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	132	383
Post-modification recorded investment	$ 3.0	$ 5.0
Average interest rate reduction	7.00%	5.00%
In offices outside North America
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	4,266	14,288
Post-modification recorded investment	$ 27.0	$ 88.0
In offices outside North America | Residential mortgages
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	172	465
Post-modification recorded investment	$ 6.0	$ 16.0
Average interest rate reduction	0.00%	0.00%
In offices outside North America | Credit cards
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	3,519	11,981
Post-modification recorded investment	$ 15.0	$ 50.0
Average interest rate reduction	27.00%	24.00%
In offices outside North America | Personal, small business and other
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	575	1,842
Post-modification recorded investment	$ 6.0	$ 22.0
Average interest rate reduction	8.00%	8.00%
Deferred principal | In North America offices
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	$ 0.0	$ 0.0
Deferred principal | In North America offices | Residential mortgages
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Deferred principal | In North America offices | Home equity loans
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Deferred principal | In North America offices | Credit cards
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Deferred principal | In North America offices | Personal, small business and other
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Deferred principal | In offices outside North America
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Deferred principal | In offices outside North America | Residential mortgages
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Deferred principal | In offices outside North America | Credit cards
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Deferred principal | In offices outside North America | Personal, small business and other
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Contingent principal forgiveness | In North America offices
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Contingent principal forgiveness | In North America offices | Residential mortgages
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Contingent principal forgiveness | In North America offices | Home equity loans
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Contingent principal forgiveness | In North America offices | Credit cards
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Contingent principal forgiveness | In North America offices | Personal, small business and other
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Contingent principal forgiveness | In offices outside North America
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Contingent principal forgiveness | In offices outside North America | Residential mortgages
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Contingent principal forgiveness | In offices outside North America | Credit cards
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Contingent principal forgiveness | In offices outside North America | Personal, small business and other
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Principal forgiveness | In North America offices
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Principal forgiveness | In North America offices | Residential mortgages
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Principal forgiveness | In North America offices | Home equity loans
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Principal forgiveness | In North America offices | Credit cards
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Principal forgiveness | In North America offices | Personal, small business and other
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Principal forgiveness | In offices outside North America
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	1.0	2.0
Principal forgiveness | In offices outside North America | Residential mortgages
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	0.0
Principal forgiveness | In offices outside North America | Credit cards
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	0.0	1.0
Principal forgiveness | In offices outside North America | Personal, small business and other
Financing Receivable, Modified [Line Items]
Post-modification recorded investment	$ 1.0	$ 1.0