Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 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	(11.90%)	(11.70%)	(11.90%)	(12.30%)
Production tax credits	(6.10%)	(7.90%)	(6.50%)	(7.70%)
Effect of rate-making on property-related differences	(4.80%)	(6.40%)	(5.10%)	(5.60%)
Other items, net	4.80%	4.30%	4.70%	3.60%
Overall income tax rate	17.00%	13.30%	16.20%	13.00%
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	(36.60%)	(33.30%)	(32.80%)	(35.60%)
Production tax credits	(8.00%)	(10.50%)	(8.20%)	(10.10%)
Effect of rate-making on property-related differences	(14.40%)	(17.40%)	(13.00%)	(15.50%)
Other items, net	4.60%	1.50%	4.60%	1.90%
Overall income tax rate	(19.40%)	(24.70%)	(14.40%)	(24.30%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
Production tax credits	(5.80%)	(7.20%)	(6.20%)	(7.00%)
Effect of rate-making on property-related differences	(0.20%)	(0.50%)	(0.70%)	(0.40%)
Other items, net	5.00%	5.80%	4.90%	4.90%
Overall income tax rate	34.00%	33.10%	33.00%	32.50%