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Regulatory Matters Regulatory Matters (Revenue Requirement Adjustment) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2014 | Jun. 30, 2013 | Jun. 30, 2014 | Jun. 30, 2013
Revenue Requirement Adjustment [Line Items] |  |  |  |
Increase to electric revenues | $ 643.9 | $ 612.1 | $ 1,319.7 | $ 1,245.3
Alliant Energy and IPL [Member] | Revenue Requirement Adjustment [Member] |  |  |  |
Revenue Requirement Adjustment [Line Items] |  |  |  |
Increase to electric revenues | $ 3.0 | $ 5.0 | $ 7.0 | $ 11.0

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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=26872669&loc=d3e20235-122688 + Details
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