Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefits	5.70%	5.70%	4.60%
Production tax credits	(7.10%)	(5.80%)	(6.60%)
Effect of rate-making on property-related differences	(6.00%)	(5.00%)	(2.00%)
Adjustment of prior period taxes	(1.30%)	0.00%	0.20%
Other items, net	(1.80%)	(1.40%)	(0.90%)
Overall income tax rate	12.40%	20.80%	16.90%
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	5.40%	5.80%	4.30%
Production tax credits	(9.50%)	(9.60%)	(9.10%)
Effect of rate-making on property-related differences	(15.90%)	(14.20%)	(5.30%)
Adjustment of prior period taxes	(3.60%)	0.20%	1.70%
Other items, net	(1.50%)	(1.60%)	(2.80%)
Overall income tax rate	(24.90%)	(15.20%)	(2.70%)
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	6.00%	5.50%	5.00%
Production tax credits	(6.30%)	(4.70%)	(6.00%)
Effect of rate-making on property-related differences	(0.80%)	(1.10%)	(0.50%)
Adjustment of prior period taxes	(0.10%)	(0.30%)	0.00%
Other items, net	(0.90%)	(0.80%)	(0.10%)
Overall income tax rate	32.90%	36.30%	33.40%
Tax Benefit Rider [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(12.10%)	(11.20%)	(8.80%)
Tax Benefit Rider [Member] | IPL [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(34.80%)	(37.00%)	(26.50%)
State Apportionment [Member]
Effective Tax Rate [Line Items]
State apportionment change due to announced sale of RMT	0.00%	3.50%	0.00%
State Apportionment [Member] | IPL [Member]
Effective Tax Rate [Line Items]
State apportionment change due to announced sale of RMT	0.00%	6.20%	0.00%
State Apportionment [Member] | WPL [Member]
Effective Tax Rate [Line Items]
State apportionment change due to announced sale of RMT	0.00%	2.70%	0.00%
Wisconsin Tax Legislation [Member]
Effective Tax Rate [Line Items]
Wisconsin tax legislation	0.00%	0.00%	(4.60%)