Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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-Topic 815
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The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

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The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

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Risk Management and Derivatives: Derivatives Not Designated as Hedge Instruments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Derivative [Line Items]
Regulatory assets	$ 379.9		$ 379.9		$ 427.7
Regulatory liabilities	576.7		576.7		568.7
Gas price derivatives
Derivative [Line Items]
Regulatory assets	1.0		1.0		$ 2.9
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (0.5)	$ 0.1	$ 0.6	$ 0.7
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold
Not Designated as Hedging Instrument \| Natural Gas
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (0.5)	$ 0.1	$ 0.6	$ 0.7
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold	Fuel, Purchased Power and Cost of Gas Sold