Commitments And Contingencies (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)
Commitments and Contingencies [Line Items]
Minimum future commitments	$ 2,387
Present value abandonment obligation	31
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	1,785
Maximum indemnification limit	17
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	587
Capital Purchase Obligation [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	36
Capital Purchase Obligation [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	5
Capital Purchase Obligation [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Minimum future commitments	31
Environmental Issue [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Environmental mitigation projects to be completed, value	6
Environmental Issue [Member] | WPL [Member]
Commitments and Contingencies [Line Items]
Environmental mitigation projects to be completed, value	$ 7
Workforce Subject to Collective Bargaining Arrangements [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	56.00%
Workforce Subject to Collective Bargaining Arrangements [Member] | IPL [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	64.00%
Workforce Subject to Collective Bargaining Arrangements Expiring within One Year [Member]
Commitments and Contingencies [Line Items]
Employees covered by collective bargaining agreement	19.00%
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%