Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) - Manufactured Gas Plant Sites [Member] $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Commitments and Contingencies [Line Items]
Minimum range of estimated future costs	$ 12
Maximum range of estimated future costs	28
Current and non-current environmental liabilities	16
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum range of estimated future costs	10
Maximum range of estimated future costs	24
Current and non-current environmental liabilities	13
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum range of estimated future costs	2
Maximum range of estimated future costs	4
Current and non-current environmental liabilities	$ 3