Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefits	5.40%	5.20%	5.40%
Effect of rate-making on property-related differences	(8.50%)	(6.80%)	(7.50%)
Production tax credits	(7.20%)	(7.20%)	(7.10%)
Adjustment of prior period taxes	(0.80%)	0.80%	(1.30%)
Other items, net	(0.50%)	(1.10%)	(1.50%)
Overall income tax rate	13.40%	15.30%	10.10%
IPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefits	6.40%	6.20%	6.10%
Effect of rate-making on property-related differences	(16.20%)	(17.20%)	(21.90%)
Production tax credits	(6.30%)	(8.30%)	(9.60%)
Adjustment of prior period taxes	(1.20%)	0.70%	(3.00%)
Other items, net	(0.30%)	(1.20%)	(1.20%)
Overall income tax rate	(2.70%)	(13.10%)	(34.20%)
WPL [Member]
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefits	5.10%	5.10%	5.10%
Effect of rate-making on property-related differences	(0.70%)	(0.50%)	(0.70%)
Production tax credits	(6.20%)	(7.10%)	(6.60%)
Adjustment of prior period taxes	(0.10%)	0.10%	0.00%
Other items, net	(0.50%)	(0.80%)	(0.80%)
Overall income tax rate	32.60%	31.80%	32.00%
IPL's tax benefit riders [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(10.00%)	(10.60%)	(12.90%)
IPL's tax benefit riders [Member] | IPL [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(20.10%)	(28.30%)	(39.60%)