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Regulatory Matters (Revenue Requirement Adjustment) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Regulatory Liabilities [Line Items] |  |  |
Electric revenues | $ 2,894.7 | $ 2,875.5 | $ 2,770.5
Alliant Energy and IPL [Member] | Revenue Requirement Adjustment [Member] |  |  |
Regulatory Liabilities [Line Items] |  |  |
Electric revenues |  | $ 14.0 | $ 14.0

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- Definition Revenue derived from the regulated (by a federal, state, or local government or agency) generation, transmission and distribution of electricity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1(b)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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- Details
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