Property, Plant, and Equipment (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment [Line Items]
Charges associated with Schahfer Generating Station Retirement	$ 3.6	$ 0.0	$ 12.2	$ 4.6
Plant and Equipment associated with Schahfer Generating Station Retirement	$ 831.8		$ 831.8

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.

No definition available.

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