Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) (Scenario, Forecast [Member], Commodity [Member])	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Electricity (MWhs) [Member]
Notional Unit Amount Of Derivatives		1,944,000	3,931,000	5,875,000
Electricity (MWhs) [Member] | IPL [Member]
Notional Unit Amount Of Derivatives		806,000	2,354,000	3,160,000
Electricity (MWhs) [Member] | WPL [Member]
Notional Unit Amount Of Derivatives		1,138,000	1,577,000	2,715,000
FTRs (MWs) [Member]
Notional Unit Amount Of Derivatives			23,000	23,000
FTRs (MWs) [Member] | IPL [Member]
Notional Unit Amount Of Derivatives			14,000	14,000
FTRs (MWs) [Member] | WPL [Member]
Notional Unit Amount Of Derivatives			9,000	9,000
Natural Gas (Dths) [Member]
Notional Unit Amount Of Derivatives	1,125,000	9,716,000	48,295,000	59,136,000
Natural Gas (Dths) [Member] | IPL [Member]
Notional Unit Amount Of Derivatives	675,000	5,554,000	30,864,000	37,093,000
Natural Gas (Dths) [Member] | WPL [Member]
Notional Unit Amount Of Derivatives	450,000	4,162,000	17,276,000	21,888,000