Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%
State income taxes, net of federal benefits	6.70%	7.50%
Production tax credits	(9.20%)	(5.50%)
Effect of rate-making on property-related differences	(5.60%)	(7.40%)
Amortization of excess deferred taxes	(0.90%)	(0.40%)
IPL's tax benefit riders	(0.70%)	(2.20%)
Other items, net	(0.70%)	(1.00%)
Overall income tax rate	10.60%	12.00%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%
State income taxes, net of federal benefits	7.20%	8.50%
Production tax credits	(14.00%)	(5.40%)
Effect of rate-making on property-related differences	(9.20%)	(13.50%)
Amortization of excess deferred taxes	(0.20%)	0.00%
IPL's tax benefit riders	(1.50%)	(4.70%)
Other items, net	0.30%	0.00%
Overall income tax rate	3.60%	5.90%
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%
State income taxes, net of federal benefits	6.20%	6.20%
Production tax credits	(4.90%)	(6.70%)
Effect of rate-making on property-related differences	(2.30%)	(2.40%)
Amortization of excess deferred taxes	(1.40%)	(0.10%)
Other items, net	(0.40%)	(0.20%)
Overall income tax rate	18.20%	17.80%