Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Dec. 31, 2019
Commitments and Contingencies [Line Items]
Minimum future commitments		$ 1,218
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments		709
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments		478
Capital Purchase Commitment [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments		95
Capital Purchase Commitment [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments		32
Capital Purchase Commitment [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments		63
Purchased Power [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]	76
Purchased Power [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]	75
Purchased Power [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]	1
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum		82
Indemnification Agreement [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum		17
Indemnification Agreement [Member] | Purchased Power [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum		$ 17
Workforce Subject to Collective Bargaining Arrangements [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement		53.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement		61.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement		82.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement		18.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement		45.00%
Credit Losses ASU [Member]
Commitments and Contingencies [Line Items]
New accounting standard, cumulative effect adjustment to retained earnings, pre-tax			$ 12
Whiting Petroleum Affiliate [Member]
Commitments and Contingencies [Line Items]
Partnership share, percent		6.00%
Obligations, maximum		$ 63
Present value abandonment obligation, discounted		40
Credit loss liability		20
Credit loss expense		$ 8
Whiting Petroleum Affiliate [Member] | Credit Losses ASU [Member]
Commitments and Contingencies [Line Items]
New accounting standard, cumulative effect adjustment to retained earnings, pre-tax			$ 12

[1] Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. As a result of an amendment to shorten the term of the DAEC PPA, Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through September 2020, and do not include the September 2020 buyout payment of $110 million.