LOANS - Schedule of Interest Income Recognized for Non-Accrual Consumer Loans (Details) - Consumer $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Financing Receivable, Nonaccrual [Line Items]
Interest income	$ 23
In North America offices
Financing Receivable, Nonaccrual [Line Items]
Interest income	23
In offices outside North America
Financing Receivable, Nonaccrual [Line Items]
Interest income	0
Residential first mortgages | In North America offices
Financing Receivable, Nonaccrual [Line Items]
Interest income	15
Residential first mortgages | In offices outside North America
Financing Receivable, Nonaccrual [Line Items]
Interest income	0
Home equity loans | In North America offices
Financing Receivable, Nonaccrual [Line Items]
Interest income	8
Credit cards | In North America offices
Financing Receivable, Nonaccrual [Line Items]
Interest income	0
Credit cards | In offices outside North America
Financing Receivable, Nonaccrual [Line Items]
Interest income	0
Personal, small business and other | In North America offices
Financing Receivable, Nonaccrual [Line Items]
Interest income	0
Personal, small business and other | In offices outside North America
Financing Receivable, Nonaccrual [Line Items]
Interest income	$ 0