Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
		May 31, 2020	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Commitments and Contingencies [Line Items]
Minimum future commitments				$ 1,270
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments				690
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments				549
Capital Purchase Commitment [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments				60
Capital Purchase Commitment [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments				8
Capital Purchase Commitment [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments				52
Purchased Power [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]			39
Purchased Power [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	[1]			38
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	82
Indemnification Agreement [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum			17	17
Indemnification Agreement [Member] | Purchased Power [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum			17	$ 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				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				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				44.00%
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	$ 63
Credit loss liability			20	20
Credit loss expense			0	$ 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
FederalEnergyRegulatoryCommission [Member]
Commitments and Contingencies [Line Items]
MISO base return on equity, percentage		10.02%			9.88%
FederalEnergyRegulatoryCommission [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Refunds related to MISO base return on equity complaints			10
FederalEnergyRegulatoryCommission [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Refunds related to MISO base return on equity complaints			$ 3

[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.