Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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	(10.10%)	(11.90%)	(9.10%)	(8.20%)
IPL's tax benefit riders	(8.30%)	(13.10%)	(8.10%)	(10.20%)
Production tax credits	(6.20%)	(9.00%)	(6.00%)	(7.20%)
Other items, net	2.80%	4.40%	3.10%	3.50%
Overall income tax rate	13.20%	5.40%	14.90%	12.90%
IPL [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	(22.60%)	(16.50%)	(20.60%)	(14.80%)
IPL's tax benefit riders	(20.90%)	(20.10%)	(20.10%)	(19.60%)
Production tax credits	(7.00%)	(6.00%)	(6.80%)	(6.10%)
Other items, net	2.30%	5.40%	2.70%	4.20%
Overall income tax rate	(13.20%)	(2.20%)	(9.80%)	(1.30%)
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	(1.90%)	(0.70%)	(1.80%)	(0.80%)
Production tax credits	(7.00%)	(5.70%)	(7.00%)	(6.10%)
Other items, net	5.50%	4.00%	4.90%	4.40%
Overall income tax rate	31.60%	32.60%	31.10%	32.50%