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Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	May 31, 2020	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019	Mar. 31, 2020
Commitments and Contingencies [Line Items]
Minimum future commitments			$ 1,219
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			627
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			561
Capital Purchase Commitment [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			21
Capital Purchase Commitment [Member] \| WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments			18
Indemnification Agreement [Member]
Commitments and Contingencies [Line Items]
Obligations, maximum		$ 74	74
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
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		68	$ 68
Credit loss liability		5	5		$ 20
Credit loss expense		$ 15	7
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			15
FederalEnergyRegulatoryCommission [Member] \| WPL [Member]
Commitments and Contingencies [Line Items]
Refunds related to MISO base return on equity complaints			$ 5