Valuation And Qualifying Accounts and Reserves (Details) - Accumulated Provision for Uncollectible Accounts [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 7.0	$ 10.0	$ 12.0
Charged to Expense	25.0	17.0	21.0
Charged to Other Accounts	9.0	2.0	1.0
Deductions	23.0	22.0	24.0
Ending Balance	18.0	7.0	10.0
IPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	1.0	3.0	1.0
Charged to Expense	18.0	16.0	21.0
Charged to Other Accounts	0.0	0.0	0.0
Deductions	18.0	18.0	19.0
Ending Balance	1.0	1.0	3.0
WPL [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	6.0	7.0	11.0
Charged to Expense	7.0	1.0	0.0
Charged to Other Accounts	9.0	2.0	1.0
Deductions	5.0	4.0	5.0
Ending Balance	$ 17.0	$ 6.0	$ 7.0