Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	35.00%
State income taxes, net of federal benefits	6.80%	7.00%	5.50%
Production tax credits	(8.60%)	(5.20%)	(6.10%)
Effect of rate-making on property-related differences	(6.10%)	(7.60%)	(8.50%)
Amortization of excess deferred taxes	(1.00%)	(0.30%)	(0.10%)
Adjustment for prior period taxes	0.60%	(2.30%)	(1.50%)
Federal Tax Reform adjustments	0.00%	(1.00%)	(3.40%)
Other items, net	(1.20%)	(0.90%)	(0.80%)
Overall income tax rate	10.80%	8.40%	12.50%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	35.00%
State income taxes, net of federal benefits	8.50%	7.70%	6.50%
Production tax credits	(13.10%)	(5.20%)	(6.70%)
Effect of rate-making on property-related differences	(9.80%)	(14.00%)	(19.10%)
Amortization of excess deferred taxes	(0.30%)	0.00%	(0.10%)
Adjustment for prior period taxes	3.10%	(4.80%)	(3.40%)
Federal Tax Reform adjustments	0.00%	(0.40%)	1.70%
Other items, net	(0.40%)	(0.60%)	(0.20%)
Overall income tax rate	7.60%	(1.20%)	(5.00%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	21.00%	21.00%	35.00%
State income taxes, net of federal benefits	6.20%	6.20%	5.10%
Production tax credits	(4.50%)	(6.40%)	(7.10%)
Effect of rate-making on property-related differences	(2.70%)	(2.30%)	(1.70%)
Amortization of excess deferred taxes	(1.80%)	(0.20%)	(0.10%)
Adjustment for prior period taxes	(0.30%)	(0.20%)	0.00%
Federal Tax Reform adjustments	0.00%	(2.30%)	(5.80%)
Other items, net	(0.40%)	(1.00%)	(0.50%)
Overall income tax rate	17.50%	14.80%	24.90%
IPL's tax benefit riders [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(0.70%)	(2.30%)	(7.60%)
IPL's tax benefit riders [Member] | IPL [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(1.40%)	(4.90%)	(18.70%)