Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
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%	5.70%	5.70%
Effect of rate-making on property-related differences	(7.50%)	(6.00%)	(5.00%)
Production tax credits	(7.10%)	(7.10%)	(5.80%)
Adjustment of prior period taxes	(1.30%)	(1.30%)	0.00%
Other items, net	(1.50%)	(1.80%)	(1.40%)
Overall income tax rate	10.10%	12.40%	20.80%
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	5.00%	5.40%	5.80%
Effect of rate-making on property-related differences	(21.90%)	(15.90%)	(14.20%)
Production tax credits	(9.80%)	(9.50%)	(9.60%)
Adjustment of prior period taxes	(3.50%)	(3.60%)	0.20%
Other items, net	(1.40%)	(1.50%)	(1.60%)
Overall income tax rate	(36.20%)	(24.90%)	(15.20%)
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	5.50%	6.00%	5.50%
Effect of rate-making on property-related differences	(0.70%)	(0.80%)	(1.10%)
Production tax credits	(6.50%)	(6.30%)	(4.70%)
Adjustment of prior period taxes	(0.10%)	(0.10%)	(0.30%)
Other items, net	(1.10%)	(0.90%)	(0.80%)
Overall income tax rate	32.10%	32.90%	36.30%
IPL's tax benefit riders [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(12.90%)	(12.10%)	(11.20%)
IPL's tax benefit riders [Member] | IPL [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(39.60%)	(34.80%)	(37.00%)
State Apportionment [Member]
Effective Tax Rate [Line Items]
State apportionment change due to announced sale of RMT	0.00%	0.00%	3.50%
State Apportionment [Member] | IPL [Member]
Effective Tax Rate [Line Items]
State apportionment change due to announced sale of RMT	0.00%	0.00%	6.20%
State Apportionment [Member] | WPL [Member]
Effective Tax Rate [Line Items]
State apportionment change due to announced sale of RMT	0.00%	0.00%	2.70%