Discontinued Operations And Assets And Liabilities Held For Sale (Components Of Assets And Liabilities Held For Sale In Consolidated Balance Sheets) (Details) - Alliant Energy and IPL [Member] - USD ($) $ in Millions		3 Months Ended	6 Months Ended
		Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Electric distribution assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Current assets		$ 9.3	$ 9.3
Property, plant and equipment, net		125.0	125.0
Non-current regulatory assets		20.5	20.5
Carrying value adjustment of net assets sold	[1]	(8.8)	(8.8)
Total assets held for sale		146.0	146.0
Current liabilities		2.4	2.4
Other liabilities		12.6	12.6
Total liabilities held for sale		15.0	15.0
Net assets held for sale		131.0	131.0
Loss on sale of Minnesota distribution assets		$ 9.0	$ 9.0
Gas distribution assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Current assets				$ 1.1
Property, plant and equipment, net				11.0
Non-current regulatory assets				7.0
Carrying value adjustment of net assets sold	[1]			0.0
Total assets held for sale				19.1
Current liabilities				1.0
Other liabilities				7.1
Total liabilities held for sale				8.1
Net assets held for sale				$ 11.0

[1] The carrying value of IPL’s Minnesota electric distribution assets classified as held for sale exceeded the expected proceeds, less costs to sell. As a result, Alliant Energy and IPL recorded a pre-tax charge of $9 million in the second quarter of 2015 related to the Minnesota electric distribution assets.