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Property, Plant and Equipment (Narrative) (Details) $ in Millions	Sep. 30, 2025 USD ($) MW
Columbia Units 1 and 2
Property, Plant and Equipment [Line Items]
Net book value, Columbia Units 1 and 2	$ 398
WPL [Member]
Property, Plant and Equipment [Line Items]
Electric capacity of solar project | MW	1,100
Construction project cost target, exceedance	$ 205
WPL [Member] | Columbia Units 1 and 2
Property, Plant and Equipment [Line Items]
Net book value, Columbia Units 1 and 2	$ 398

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Electric Capacity of Solar Project

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A

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