Income Taxes (Schedule Of Effective Income Tax Rates) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effective Tax Rate [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefits	5.20%	5.40%	5.70%
Effect of rate-making on property-related differences	(6.80%)	(7.50%)	(6.00%)
Production tax credits	(7.20%)	(7.10%)	(7.10%)
Adjustment of prior period taxes	0.80%	(1.30%)	(1.30%)
Other items, net	(1.10%)	(1.50%)	(1.80%)
Overall income tax rate	15.30%	10.10%	12.40%
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	6.20%	6.10%	6.30%
Effect of rate-making on property-related differences	(17.20%)	(21.90%)	(15.90%)
Production tax credits	(8.30%)	(9.60%)	(9.30%)
Adjustment of prior period taxes	0.70%	(3.00%)	(3.60%)
Other items, net	(1.20%)	(1.20%)	(1.60%)
Overall income tax rate	(13.10%)	(34.20%)	(23.90%)
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%	5.50%
Effect of rate-making on property-related differences	(0.50%)	(0.70%)	(0.80%)
Production tax credits	(7.10%)	(6.60%)	(6.40%)
Adjustment of prior period taxes	0.10%	0.00%	(0.20%)
Other items, net	(0.80%)	(0.80%)	(0.80%)
Overall income tax rate	31.80%	32.00%	32.30%
IPL's tax benefit riders [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(10.60%)	(12.90%)	(12.10%)
IPL's tax benefit riders [Member] | IPL [Member]
Effective Tax Rate [Line Items]
IPL’s tax benefit riders	(28.30%)	(39.60%)	(34.80%)