Derivative Instruments (Notional Amounts Of Derivative Instruments) (Details) (Commodity [Member])	Sep. 30, 2014 MWh
Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	10,219,000
Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	2,724,000
Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	7,495,000
FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	15,233,000
FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	8,898,000
FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	6,335,000
Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	71,361,000
Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	47,679,000
Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	23,682,000
Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	6,411,000
Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,832,000
Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	4,579,000
2014 [Member] | Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	2,092,000
2014 [Member] | Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,046,000
2014 [Member] | Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,046,000
2014 [Member] | FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	5,673,000
2014 [Member] | FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	3,340,000
2014 [Member] | FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	2,333,000
2014 [Member] | Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	25,806,000
2014 [Member] | Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	17,823,000
2014 [Member] | Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	7,983,000
2014 [Member] | Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	836,000
2014 [Member] | Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	266,000
2014 [Member] | Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	570,000
2015 [Member] | Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	3,946,000
2015 [Member] | Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,678,000
2015 [Member] | Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	2,268,000
2015 [Member] | FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	9,560,000
2015 [Member] | FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	5,558,000
2015 [Member] | FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	4,002,000
2015 [Member] | Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	36,532,000
2015 [Member] | Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	25,776,000
2015 [Member] | Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	10,756,000
2015 [Member] | Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,490,000
2015 [Member] | Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	75,000
2015 [Member] | Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,415,000
2016 [Member] | Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,553,000
2016 [Member] | Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2016 [Member] | Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,553,000
2016 [Member] | FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2016 [Member] | FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2016 [Member] | FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2016 [Member] | Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	8,805,000
2016 [Member] | Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	3,862,000
2016 [Member] | Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	4,943,000
2016 [Member] | Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,899,000
2016 [Member] | Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	830,000
2016 [Member] | Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,069,000
2017 [Member] | Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,314,000
2017 [Member] | Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2017 [Member] | Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,314,000
2017 [Member] | FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2017 [Member] | FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2017 [Member] | FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2017 [Member] | Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	218,000
2017 [Member] | Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	218,000
2017 [Member] | Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2017 [Member] | Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,073,000
2017 [Member] | Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	274,000
2017 [Member] | Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	799,000
2018 [Member] | Electricity (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,314,000
2018 [Member] | Electricity (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2018 [Member] | Electricity (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,314,000
2018 [Member] | FTRs (MWhs) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2018 [Member] | FTRs (MWhs) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2018 [Member] | FTRs (MWhs) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2018 [Member] | Natural Gas (Dths) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2018 [Member] | Natural Gas (Dths) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2018 [Member] | Natural Gas (Dths) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	0
2018 [Member] | Coal (Tons) [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	1,113,000
2018 [Member] | Coal (Tons) [Member] | IPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	387,000
2018 [Member] | Coal (Tons) [Member] | WPL [Member]
Notional Amount of Derivatives [Line Items]
Notional unit amount of derivatives (in MWhs/Dths/Tons)	726,000