LOANS - Consumer Troubled Debt Restructurings (Details) - Consumer $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) loan	Mar. 31, 2021 USD ($) loan
Loans receivable
Period within which default occurred post-modification	1 year
Number of days past due, non-accrual status	60 days
In North America offices
Loans receivable
Number of loans modified | loan	41,336	59,902
Post-modification recorded investment	$ 264	$ 373
TDR loans in payment default	$ 61	$ 86
In North America offices | Residential mortgages
Loans receivable
Number of loans modified | loan	346	336
Post-modification recorded investment	$ 81	$ 60
Average interest rate reduction	0.00%	0.00%
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 1	$ 3
TDR loans in payment default	4	18
In North America offices | Residential mortgages | New OCC guidance
Loans receivable
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 1	$ 1
In North America offices | Home equity loans
Loans receivable
Number of loans modified | loan	104	59
Post-modification recorded investment	$ 9	$ 6
Average interest rate reduction	0.00%	0.00%
TDR loans in payment default	$ 0	$ 4
In North America offices | Credit cards
Loans receivable
Number of loans modified | loan	40,740	59,046
Post-modification recorded investment	$ 173	$ 300
Average interest rate reduction	17.00%	17.00%
TDR loans in payment default	$ 57	$ 63
In North America offices | Personal, small business and other
Loans receivable
Number of loans modified | loan	146	461
Post-modification recorded investment	$ 1	$ 7
Average interest rate reduction	5.00%	4.00%
TDR loans in payment default	$ 0	$ 1
In offices outside North America
Loans receivable
Number of loans modified | loan	5,855	32,604
Post-modification recorded investment	$ 37	$ 184
TDR loans in payment default	$ 9	$ 86
In offices outside North America | Residential mortgages
Loans receivable
Number of loans modified | loan	183	467
Post-modification recorded investment	$ 6	$ 24
Average interest rate reduction	0.00%	1.00%
TDR loans in payment default	$ 4	$ 12
In offices outside North America | Credit cards
Loans receivable
Number of loans modified | loan	5,000	24,599
Post-modification recorded investment	$ 22	$ 102
Average interest rate reduction	19.00%	16.00%
TDR loans in payment default	$ 4	$ 52
In offices outside North America | Personal, small business and other
Loans receivable
Number of loans modified | loan	672	7,538
Post-modification recorded investment	$ 9	$ 58
Average interest rate reduction	8.00%	10.00%
TDR loans in payment default	$ 1	$ 22
Deferred principal | In North America offices
Loans receivable
Post-modification recorded investment	0	0
Deferred principal | In North America offices | Residential mortgages
Loans receivable
Post-modification recorded investment	0	0
Deferred principal | In North America offices | Home equity loans
Loans receivable
Post-modification recorded investment	0	0
Deferred principal | In North America offices | Credit cards
Loans receivable
Post-modification recorded investment	0	0
Deferred principal | In North America offices | Personal, small business and other
Loans receivable
Post-modification recorded investment	0	0
Deferred principal | In offices outside North America
Loans receivable
Post-modification recorded investment	0	0
Deferred principal | In offices outside North America | Residential mortgages
Loans receivable
Post-modification recorded investment	0	0
Deferred principal | In offices outside North America | Credit cards
Loans receivable
Post-modification recorded investment	0	0
Deferred principal | In offices outside North America | Personal, small business and other
Loans receivable
Post-modification recorded investment	0	0
Contingent principal forgiveness | In North America offices
Loans receivable
Post-modification recorded investment	0	0
Contingent principal forgiveness | In North America offices | Residential mortgages
Loans receivable
Post-modification recorded investment	0	0
Contingent principal forgiveness | In North America offices | Home equity loans
Loans receivable
Post-modification recorded investment	0	0
Contingent principal forgiveness | In North America offices | Credit cards
Loans receivable
Post-modification recorded investment	0	0
Contingent principal forgiveness | In North America offices | Personal, small business and other
Loans receivable
Post-modification recorded investment	0	0
Contingent principal forgiveness | In offices outside North America
Loans receivable
Post-modification recorded investment	0	0
Contingent principal forgiveness | In offices outside North America | Residential mortgages
Loans receivable
Post-modification recorded investment	0	0
Contingent principal forgiveness | In offices outside North America | Credit cards
Loans receivable
Post-modification recorded investment	0	0
Contingent principal forgiveness | In offices outside North America | Personal, small business and other
Loans receivable
Post-modification recorded investment	0	0
Principal forgiveness | In North America offices
Loans receivable
Post-modification recorded investment	0	0
Principal forgiveness | In North America offices | Residential mortgages
Loans receivable
Post-modification recorded investment	0	0
Principal forgiveness | In North America offices | Home equity loans
Loans receivable
Post-modification recorded investment	0	0
Principal forgiveness | In North America offices | Credit cards
Loans receivable
Post-modification recorded investment	0	0
Principal forgiveness | In North America offices | Personal, small business and other
Loans receivable
Post-modification recorded investment	0	0
Principal forgiveness | In offices outside North America
Loans receivable
Post-modification recorded investment	1	9
Principal forgiveness | In offices outside North America | Residential mortgages
Loans receivable
Post-modification recorded investment	0	0
Principal forgiveness | In offices outside North America | Credit cards
Loans receivable
Post-modification recorded investment	1	7
Principal forgiveness | In offices outside North America | Personal, small business and other
Loans receivable
Post-modification recorded investment	$ 0	$ 2