LOANS AND LEASES - Loans Held For Sale (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale, at fair value	$ 1,946	$ 1,219
Other loans held for sale	1,384	101
Residential loans held for sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale, at fair value	1,778	967
Other loans held for sale	1,101	0
Commercial loans held for sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale, at fair value	168	252
Other loans held for sale	283	$ 101
Loan Portfolio Transfer, One | Residential loans held for sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other loans held for sale	524
Loan Portfolio Transfer, Two | Residential loans held for sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other loans held for sale	$ 575