Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Millions	Jun. 30, 2025 USD ($)
State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	$ 323
Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	678
IPL [Member] \| State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	7
IPL [Member] \| Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	437
WPL [Member] \| State [Member]
Carryforwards [Line Items]
Net operating losses, carryforward amount	1
WPL [Member] \| Federal [Member]
Carryforwards [Line Items]
Tax credits, carryforward amount	$ 228

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-3

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