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Risk Management Activities (Narrative) (Details) mMDth in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) mMDth	Dec. 31, 2023 USD ($) mMDth	Jun. 08, 2023 USD ($)	Mar. 24, 2023 USD ($)
Derivative [Line Items]
Limit of GCA Volumes	20.00%
Derivative Asset	$ 27.0	$ 23.3
Senior Notes	12,103.0	10,853.0
Derivative Asset, Subject to Master Netting Arrangement, after Offset	$ 23.5	13.9
Customer annual demand	20.00%
Other Current Assets
Derivative [Line Items]
Derivative Asset	$ 9.1	$ 1.1
NiSource
Derivative [Line Items]
Senior Notes			$ 450.0
Senior Notes \| NiSource
Derivative [Line Items]
Senior Notes	$ 1,050.0		$ 300.0	$ 750.0
Debt, Weighted Average Interest Rate			5.25%	5.25%
Minimum
Derivative [Line Items]
Commodity Contract Length	1 year
Maximum
Derivative [Line Items]
Commodity Contract Length	3 years
Natural Gas
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount \| mMDth	77.8	76.1