Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
IPL's tax benefit riders	(13.00%)	(12.90%)	(12.40%)	(12.60%)
Effect of rate-making on property-related differences	(8.60%)	(6.20%)	(6.70%)	(5.90%)
Production tax credits	(6.80%)	(7.70%)	(6.60%)	(7.70%)
Other items, net	0.70%	1.60%	2.90%	2.60%
Overall income tax rate	7.30%	9.80%	12.20%	11.40%
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	(39.20%)	(38.90%)	(36.50%)	(37.80%)
Effect of rate-making on property-related differences	(22.40%)	(16.50%)	(18.40%)	(16.10%)
Production tax credits	(9.30%)	(10.60%)	(8.80%)	(10.40%)
Other items, net	2.20%	0.40%	3.20%	0.80%
Overall income tax rate	(33.70%)	(30.60%)	(25.50%)	(28.50%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
Effect of rate-making on property-related differences	(0.80%)	(1.40%)	(0.70%)	(0.80%)
Production tax credits	(6.20%)	(6.60%)	(6.20%)	(6.90%)
Other items, net	0.00%	3.70%	3.00%	4.40%
Overall income tax rate	28.00%	30.70%	31.10%	31.70%