Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%
IPL's tax benefit riders	(11.90%)	(12.80%)
Production tax credits	(6.70%)	(7.50%)
Effect of rate-making on property-related differences	(5.30%)	(5.00%)
Other items, net	4.60%	3.00%
Overall income tax rate	15.70%	12.70%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%
IPL's tax benefit riders	(31.20%)	(37.30%)
Production tax credits	(8.30%)	(9.70%)
Effect of rate-making on property-related differences	(12.40%)	(14.00%)
Other items, net	4.70%	2.00%
Overall income tax rate	(12.20%)	(24.00%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%
Production tax credits	(6.40%)	(6.90%)
Effect of rate-making on property-related differences	(1.00%)	(0.30%)
Other items, net	4.80%	4.20%
Overall income tax rate	32.40%	32.00%