Commitments And Contingencies (MPG Site Estimated Future Costs And Recorded Liabilities) (Details) (Manufactured Gas Plant Sites [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies [Line Items]
Minimum range of estimated future costs	$ 14
Maximum range of estimated future costs	34
Current and non-current environmental liabilities	16
IPL [Member]
Commitments and Contingencies [Line Items]
Minimum range of estimated future costs	13
Maximum range of estimated future costs	31
Current and non-current environmental liabilities	14
WPL [Member]
Commitments and Contingencies [Line Items]
Minimum range of estimated future costs	1
Maximum range of estimated future costs	3
Current and non-current environmental liabilities	$ 2