DERIVATIVE FINANCIAL INSTRUMENTS - Financial Assets and Liabilities that are Offset (Details) $ in Millions	9 Months Ended
Sep. 30, 2025 USD ($) group	Dec. 31, 2024 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Number of primary groups \| group	2
Aggregate credit risk, net of collateral	$ 28	$ 192
Investment securities and cash collateral pledged by Huntington	111
Investment securities and cash collateral pledged to Huntington	$ 150

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 185
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-185

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4H
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4H

Name:	us-gaap_CollateralAlreadyPostedAggregateFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant