LOANS AND LEASES - Narrative (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable on loans and leases held for investment		$ 857		$ 857		$ 816
Loans pledged as collateral for FHLB borrowed funds	[1]	138,898		138,898		137,142
Interest income on direct financing lease		11	$ 11	33	$ 31
Retail | Residential mortgages | Federal Home Loan Bank Advances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral for FHLB borrowed funds		40,600		40,600		37,500
Consumer and Commercial Portfolio Segment | Education, commercial and industrial, and commercial real estate loans | Notes Payable, Other Payables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral for FHLB borrowed funds		$ 20,000		$ 20,000		$ 22,900

[1] Includes amounts in consolidated VIEs. See Note 6 for additional information.