LOANS - Consumer Loans Troubled Debt Restructurings (Details) - Consumer $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2022 USD ($) loan	Jun. 30, 2022 USD ($) loan
In North America offices
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	37,307	78,643
Post-modification recorded investment	$ 221.0	$ 485.0
In North America offices | Residential mortgages
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	279	625
Post-modification recorded investment	$ 56.0	$ 137.0
Average interest rate reduction	0.00%	0.00%
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 0.4	$ 2.0
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	$ 0.4	$ 2.0
In North America offices | Home equity loans
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	103	207
Post-modification recorded investment	$ 7.0	$ 16.0
Average interest rate reduction	0.00%	0.00%
In North America offices | Credit cards
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	36,820	77,560
Post-modification recorded investment	$ 157.0	$ 330.0
Average interest rate reduction	18.00%	17.00%
In North America offices | Personal, small business and other
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	105	251
Post-modification recorded investment	$ 1.0	$ 2.0
Average interest rate reduction	5.00%	5.00%
In offices outside North America
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	4,167	10,022
Post-modification recorded investment	$ 24.0	$ 61.0
In offices outside North America | Residential mortgages
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	110	293
Post-modification recorded investment	$ 4.0	$ 10.0
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	3,462	8,462
Post-modification recorded investment	$ 13.0	$ 35.0
Average interest rate reduction	27.00%	23.00%
In offices outside North America | Personal, small business and other
Financing Receivable, Modified [Line Items]
Number of loans modified | loan	595	1,267
Post-modification recorded investment	$ 7.0	$ 16.0
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	0.0	1.0
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	$ 0.0	$ 0.0