Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
IPL's tax benefit riders	(13.10%)	(11.00%)	(10.20%)	(10.60%)
Effect of rate-making on property-related differences	(11.90%)	(7.10%)	(8.20%)	(7.10%)
Production tax credits	(9.00%)	(6.70%)	(7.20%)	(6.60%)
Other items, net	4.40%	3.00%	3.50%	3.70%
Overall income tax rate	5.40%	13.20%	12.90%	14.40%
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	(20.10%)	(30.00%)	(19.60%)	(28.20%)
Effect of rate-making on property-related differences	(16.50%)	(18.70%)	(14.80%)	(17.90%)
Production tax credits	(6.00%)	(8.60%)	(6.10%)	(8.00%)
Other items, net	5.40%	3.70%	4.20%	4.20%
Overall income tax rate	(2.20%)	(18.60%)	(1.30%)	(14.90%)
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	(0.70%)	(0.70%)	(0.80%)	(0.60%)
Production tax credits	(5.70%)	(6.10%)	(6.10%)	(6.30%)
Other items, net	4.00%	4.10%	4.40%	4.20%
Overall income tax rate	32.60%	32.30%	32.50%	32.30%