INCOME TAXES (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Reduction in income tax expense for the amortization of the regulatory liability associated with excess ADIT that was returned to customers	$ 1,700	$ 1,500	$ 11,900	$ 13,400

Reduction in income tax expense for the amortization of the regulatory liability associated with excess ADIT that was returned to customers

No definition available.

Name:	ogs_ReductioninincometaxexpensefortheamortizationoftheregulatoryliabilityassociatedwithexcessADITthatwasreturnedtocustomers
Namespace Prefix:	ogs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration