Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 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	(7.90%)	(10.60%)	(8.40%)	(10.20%)
Production tax credits	(5.70%)	(6.50%)	(6.00%)	(6.40%)
Effect of rate-making on property-related differences	(4.90%)	(8.40%)	(5.90%)	(7.00%)
Other items, net	0.70%	4.10%	2.80%	4.30%
Overall income tax rate	17.20%	13.60%	17.50%	15.70%
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	(16.60%)	(25.30%)	(19.00%)	(25.20%)
Production tax credits	(5.30%)	(7.20%)	(6.10%)	(7.10%)
Effect of rate-making on property-related differences	(8.80%)	(22.30%)	(12.50%)	(16.60%)
Other items, net	(2.00%)	5.30%	2.60%	4.90%
Overall income tax rate	2.30%	(14.50%)	0.00%	(9.00%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
Production tax credits	(6.30%)	(6.90%)	(6.40%)	(6.50%)
Effect of rate-making on property-related differences	(1.00%)	(0.70%)	(0.90%)	(0.60%)
Other items, net	4.50%	4.50%	4.70%	4.40%
Overall income tax rate	32.20%	31.90%	32.40%	32.30%