LOANS - Corporate Loan Modifications to Borrowers Experiencing Financial Difficulty (Details) - Corporate loans - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Financing Receivable, Modified [Line Items]
Total modifications balance	$ 60		$ 178
Commitments to lend	1,000		1,000
Term extension
Financing Receivable, Modified [Line Items]
Total modifications balance	60		154
Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total modifications balance	0		24
Commercial and industrial
Financing Receivable, Modified [Line Items]
Total modifications balance	$ 25		$ 93
Weighted average term extension	22 months		28 months
Commercial and industrial | Term extension
Financing Receivable, Modified [Line Items]
Total modifications balance	$ 25		$ 70
Commercial and industrial | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total modifications balance	0		23
Financial institutions
Financing Receivable, Modified [Line Items]
Total modifications balance	0		0
Financial institutions | Term extension
Financing Receivable, Modified [Line Items]
Total modifications balance	0		0
Financial institutions | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total modifications balance	0		0
Mortgage and real estate
Financing Receivable, Modified [Line Items]
Total modifications balance	$ 35	$ 1	$ 85	$ 1
Weighted average term extension	55 months		37 months
Mortgage and real estate | Term extension
Financing Receivable, Modified [Line Items]
Total modifications balance	$ 35	1	$ 84	1
Mortgage and real estate | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total modifications balance	0	$ 0	1	$ 0
Other
Financing Receivable, Modified [Line Items]
Total modifications balance	0		0
Other | Term extension
Financing Receivable, Modified [Line Items]
Total modifications balance	0		0
Other | Combination: term extension and payment delay
Financing Receivable, Modified [Line Items]
Total modifications balance	$ 0		$ 0