Commitments And Contingencies (Narrative) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1,327
Present value abandonment obligation	37
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	773
Indemnification obligations, maximum	17
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	543
Capital Purchase Obligation [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	268
Capital Purchase Obligation [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	237
Capital Purchase Obligation [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	31
Purchased Power [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	184	[1]
Purchased Power [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	183	[1]
Purchased Power [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1	[1]
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Indemnification obligations, maximum	90
Indemnification Agreement [Member] | Purchased Power [Member]
Commitments and Contingencies [Line Items]
Indemnification obligations, maximum	$ 17
Workforce Subject to Collective Bargaining Arrangements [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	54.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	60.00%
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	27.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	82.00%
Notice to cancel extension	30 days

[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.