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BORROWINGS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
BORROWINGS - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2025	Mar. 31, 2025	Sep. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Carrying value of assets pledged as collateral against repurchase agreements	$ 205		$ 205	$ 224
Maturity term			60 days
Auto Loan Securitization Trust
Debt Instrument [Line Items]
Weighted average rate	5.22%		5.22%
Auto Loan Securitization Trust \| Huntington National Bank Unsecured Notes Maturing March 2033
Debt Instrument [Line Items]
Reference pool		$ 3,500
Auto Loan Securitization Trust \| Huntington National Bank Unsecured Notes Maturing August 2033
Debt Instrument [Line Items]
Reference pool	$ 3,500		$ 3,500
Credit Linked Notes \| Huntington National Bank Unsecured Notes Maturing March 2033
Debt Instrument [Line Items]
Debt face amount		$ 415
Debt stated interest rate		4.957%
Credit Linked Notes \| Huntington National Bank Unsecured Notes Maturing March 2033 \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		2.25%
Credit Linked Notes \| Huntington National Bank Unsecured Notes Maturing March 2033 \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		7.15%
Credit Linked Notes \| Huntington National Bank Unsecured Notes Maturing March 2033 \| Weighted average
Debt Instrument [Line Items]
Basis spread on variable rate		4.28%
Credit Linked Notes \| Huntington National Bank Unsecured Notes Maturing August 2033
Debt Instrument [Line Items]
Debt face amount	$ 415		$ 415
Debt stated interest rate	4.835%		4.835%
Credit Linked Notes \| Huntington National Bank Unsecured Notes Maturing August 2033 \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.20%
Credit Linked Notes \| Huntington National Bank Unsecured Notes Maturing August 2033 \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	6.60%
Credit Linked Notes \| Huntington National Bank Unsecured Notes Maturing August 2033 \| Weighted average
Debt Instrument [Line Items]
Basis spread on variable rate	3.04%
Senior Notes \| Fixed-to-Floating Senior Notes Due April 12, 2028
Debt Instrument [Line Items]
Debt face amount		$ 1,000
Debt stated interest rate		4.871%
Basis spread on variable rate		0.726%
Senior Notes \| Floating Senior Notes Due April 12, 2028
Debt Instrument [Line Items]
Debt face amount		$ 500
Basis spread on variable rate		0.72%