LOANS - Corporate Loan Modifications to Borrowers Experiencing Financial Difficulty (Details) - Corporate $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Financing receivable impaired
Total modifications balance	$ 342
Commitments to lend	1,200
Term extension
Financing receivable impaired
Total modifications balance	323
Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	19
Commercial and industrial
Financing receivable impaired
Total modifications balance	$ 198
Weighted- average term extension (months)	19 months
Commercial and industrial | Term extension
Financing receivable impaired
Total modifications balance	$ 180
Commercial and industrial | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	18
Financial institutions
Financing receivable impaired
Total modifications balance	0
Financial institutions | Term extension
Financing receivable impaired
Total modifications balance	0
Financial institutions | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	0
Mortgage and real estate
Financing receivable impaired
Total modifications balance	$ 144
Weighted- average term extension (months)	24 months
Mortgage and real estate | Term extension
Financing receivable impaired
Total modifications balance	$ 143
Mortgage and real estate | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	1
Other
Financing receivable impaired
Total modifications balance	0
Other | Term extension
Financing receivable impaired
Total modifications balance	0
Other | Combination: term extension and payment delay
Financing receivable impaired
Total modifications balance	$ 0