Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	35.00%	21.00%	35.00%
State income taxes, net of federal benefits	6.90%	5.70%	6.90%	5.60%
Effect of rate-making on property-related differences	(6.30%)	(10.10%)	(6.70%)	(9.10%)
Production tax credits	(5.40%)	(6.20%)	(5.40%)	(6.00%)
Adjustment for prior period taxes	(5.70%)	(2.00%)	(2.60%)	(1.30%)
IPL's tax benefit riders	(2.30%)	(8.30%)	(2.20%)	(8.10%)
Federal Tax Reform adjustments	(2.50%)	0.00%	(1.20%)	0.00%
Other items, net	(0.40%)	(0.90%)	(1.00%)	(1.20%)
Overall income tax rate	5.30%	13.20%	8.80%	14.90%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	35.00%	21.00%	35.00%
State income taxes, net of federal benefits	7.70%	6.50%	7.70%	6.50%
Effect of rate-making on property-related differences	(11.50%)	(22.60%)	(12.00%)	(20.60%)
Production tax credits	(5.50%)	(7.00%)	(5.40%)	(6.80%)
Adjustment for prior period taxes	(10.20%)	(3.50%)	(5.40%)	(3.30%)
IPL's tax benefit riders	(4.80%)	(20.90%)	(4.60%)	(20.10%)
Federal Tax Reform adjustments	(0.90%)	0.00%	(0.50%)	0.00%
Other items, net	(0.60%)	(0.70%)	(1.00%)	(0.50%)
Overall income tax rate	(4.80%)	(13.20%)	(0.20%)	(9.80%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	35.00%	21.00%	35.00%
State income taxes, net of federal benefits	6.20%	5.20%	6.20%	5.10%
Effect of rate-making on property-related differences	(2.10%)	(1.90%)	(2.30%)	(1.80%)
Production tax credits	(6.40%)	(7.00%)	(6.60%)	(7.00%)
Adjustment for prior period taxes	(0.00%)	0.80%	(0.00%)	0.30%
Federal Tax Reform adjustments	(6.40%)	0.00%	(2.80%)	0.00%
Other items, net	(0.50%)	(0.50%)	(1.30%)	(0.50%)
Overall income tax rate	11.80%	31.60%	14.20%	31.10%