Commitments And Contingencies (Other Purchase Obligations) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 2,303
Individual commitments incurred	1
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1,707
Individual commitments incurred	1
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	588
Individual commitments incurred	1
Purchased Power [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1,278	[1]
Purchased Power [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1,194	[1]
Purchased Power [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	84	[1]
Natural gas [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	847
Natural gas [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	422
Natural gas [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	425
Coal [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	144	[2]
Coal [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	66	[2]
Coal [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	78	[2]
Other [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	34	[3]
Other [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	25	[3]
Other [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 1	[3]

[1] Includes payments required by purchased power agreements for capacity rights and minimum quantities of MWhs required to be purchased.

[2] Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2017 regarding expected future usage, which is subject to change.

[3] Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2017.