Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	7.50%	6.50%	7.20%	7.10%
Production tax credits	(8.50%)	(5.40%)	(8.90%)	(5.50%)
Effect of rate-making on property-related differences	(6.20%)	(6.70%)	(6.00%)	(7.20%)
Amortization of excess deferred taxes	(1.30%)	(0.40%)	(1.10%)	(0.40%)
IPL's tax benefit riders	(0.70%)	(2.10%)	(0.70%)	(2.20%)
Other items, net	(1.50%)	(1.20%)	(1.00%)	(1.00%)
Overall income tax rate	10.30%	11.70%	10.50%	11.80%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	8.30%	7.00%	8.10%	7.70%
Production tax credits	(13.20%)	(5.30%)	(13.60%)	(5.30%)
Effect of rate-making on property-related differences	(10.10%)	(11.50%)	(9.60%)	(12.40%)
Amortization of excess deferred taxes	(0.40%)	0.00%	(0.30%)	0.00%
IPL's tax benefit riders	(1.40%)	(4.30%)	(1.40%)	(4.50%)
Other items, net	(0.40%)	(2.80%)	(0.50%)	(1.50%)
Overall income tax rate	3.80%	4.10%	3.70%	5.00%
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	21.00%	21.00%
State income taxes, net of federal benefits	6.20%	6.20%	6.20%	6.20%
Production tax credits	(4.20%)	(6.80%)	(4.60%)	(6.70%)
Effect of rate-making on property-related differences	(2.70%)	(2.70%)	(2.40%)	(2.50%)
Amortization of excess deferred taxes	(2.30%)	(0.10%)	(1.80%)	(0.10%)
Other items, net	(2.50%)	(4.10%)	(1.20%)	(1.90%)
Overall income tax rate	15.50%	13.50%	17.20%	16.00%