Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 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	7.00%	6.90%	7.10%	6.90%
Production tax credits	(9.30%)	(5.40%)	(9.10%)	(5.40%)
Effect of rate-making on property-related differences	(5.60%)	(6.30%)	(5.70%)	(6.70%)
Amortization of excess deferred taxes	(1.10%)	(0.10%)	(1.10%)	(0.30%)
Adjustment for prior period taxes	(1.80%)	(5.70%)	(0.70%)	(2.60%)
IPL's tax benefit riders	(0.80%)	(2.30%)	(0.70%)	(2.20%)
Federal Tax Reform adjustments	0.00%	(2.50%)	0.00%	(1.20%)
Other items, net	(0.20%)	(0.30%)	(1.00%)	(0.70%)
Overall income tax rate	9.20%	5.30%	9.80%	8.80%
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	8.10%	7.70%	8.10%	7.70%
Production tax credits	(14.70%)	(5.50%)	(14.30%)	(5.40%)
Effect of rate-making on property-related differences	(9.00%)	(11.50%)	(9.30%)	(12.00%)
Amortization of excess deferred taxes	(0.30%)	0.00%	(0.30%)	0.00%
Adjustment for prior period taxes	1.30%	(10.20%)	0.60%	(5.40%)
IPL's tax benefit riders	(1.50%)	(4.80%)	(1.50%)	(4.60%)
Federal Tax Reform adjustments	0.00%	(0.90%)	0.00%	(0.50%)
Other items, net	(0.30%)	(0.60%)	(0.10%)	(1.00%)
Overall income tax rate	4.60%	(4.80%)	4.20%	(0.20%)
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	(4.40%)	(6.40%)	(4.50%)	(6.60%)
Effect of rate-making on property-related differences	(2.80%)	(2.10%)	(2.60%)	(2.30%)
Amortization of excess deferred taxes	(1.70%)	(0.10%)	(1.70%)	(0.10%)
Adjustment for prior period taxes	0.40%	0.00%	(0.30%)	0.00%
Federal Tax Reform adjustments	0.00%	(6.40%)	0.00%	(2.80%)
Other items, net	(0.20%)	(0.40%)	(0.40%)	(1.20%)
Overall income tax rate	18.50%	11.80%	17.70%	14.20%

Effective Income Tax Rate Reconciliation Amortization Of Excess Deferred Taxes

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