Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
IPL's tax benefit riders	(12.90%)	(10.30%)	(12.60%)	(11.00%)
Production tax credits	(7.70%)	(5.50%)	(7.70%)	(6.00%)
Effect of rate-making on property-related differences	(6.20%)	(4.70%)	(5.90%)	(4.30%)
Other items, net	1.60%	5.90%	2.60%	6.00%
Overall income tax rate	9.80%	20.40%	11.40%	24.00%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
IPL's tax benefit riders	(38.90%)	(34.20%)	(37.80%)	(34.50%)
Production tax credits	(10.60%)	(8.60%)	(10.40%)	(8.60%)
Effect of rate-making on property-related differences	(16.50%)	(11.20%)	(16.10%)	(10.60%)
Other items, net	0.40%	6.40%	0.80%	6.20%
Overall income tax rate	(30.60%)	(12.60%)	(28.50%)	(5.60%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
IPL's tax benefit riders	0.00%	0.00%	0.00%	0.00%
Production tax credits	(6.60%)	(4.30%)	(6.90%)	(5.50%)
Effect of rate-making on property-related differences	(1.40%)	(1.10%)	(0.80%)	(1.50%)
Other items, net	3.70%	5.90%	4.40%	6.20%
Overall income tax rate	30.70%	35.50%	31.70%	37.70%
State Apportionment [Member]
Effective Tax Rate [Line Items]
State apportionment change due to planned sale of RMT			0.00%	4.30%
State Apportionment [Member] | IPL [Member]
Effective Tax Rate [Line Items]
State apportionment change due to planned sale of RMT			0.00%	6.90%
State Apportionment [Member] | WPL [Member]
Effective Tax Rate [Line Items]
State apportionment change due to planned sale of RMT			0.00%	3.50%