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Property, Plant and Equipment (Electric Plant) (Details) (USD $) In Millions, unless otherwise specified |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 12 Months Ended
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Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2013 Generation [Member] | Dec. 31, 2012 Generation [Member] | Dec. 31, 2013 Distribution [Member] | Dec. 31, 2012 Distribution [Member] | Dec. 31, 2013 Other [Member] | Dec. 31, 2012 Other [Member] | Dec. 31, 2013 IPL [Member] | Dec. 31, 2012 IPL [Member] | Dec. 31, 2013 IPL [Member] Generation [Member] | Dec. 31, 2012 IPL [Member] Generation [Member] | Dec. 31, 2013 IPL [Member] Distribution [Member] | Dec. 31, 2012 IPL [Member] Distribution [Member] | Dec. 31, 2013 IPL [Member] Other [Member] | Dec. 31, 2012 IPL [Member] Other [Member] | Dec. 31, 2013 IPL [Member] George Neal Unit 4 [Member] | Dec. 31, 2013 WPL [Member] | Dec. 31, 2012 WPL [Member] | Dec. 31, 2013 WPL [Member] Generation [Member] | Dec. 31, 2012 WPL [Member] Generation [Member] | Dec. 31, 2013 WPL [Member] Distribution [Member] | Dec. 31, 2012 WPL [Member] Distribution [Member] | Dec. 31, 2013 WPL [Member] Other [Member] | Dec. 31, 2012 WPL [Member] Other [Member] | Dec. 31, 2013 WPL [Member] Edgewater Unit 3 and Nelson Dewey Units 1 and 2 [Member]
Property, Plant and Equipment [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Plant in service |  |  | $ 4,792.0 | $ 4,798.9 | $ 4,179.6 | $ 3,981.5 | $ 286.3 | $ 290.3 |  |  | $ 2,513.2 | $ 2,393.0 | $ 2,311.2 | $ 2,205.9 | $ 210.5 | $ 216.3 |  |  |  | $ 2,278.8 | $ 2,405.9 | $ 1,868.4 | $ 1,775.6 | $ 75.8 | $ 74.0 |
Plant anticipated to be retired early | 157.8 | 0 |  |  |  |  |  |  | 0 | 0 |  |  |  |  |  |  |  | 157.8 | 0 |  |  |  |  |  |  |
Electric plant | $ 9,415.7 | $ 9,070.7 |  |  |  |  |  |  | $ 5,034.9 | $ 4,815.2 |  |  |  |  |  |  | $ 61.0 | $ 4,380.8 | $ 4,255.5 |  |  |  |  |  |  |
Property, plant and equipment, useful life |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years

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- Definition Carrying amount as of the balance sheet date of long-lived, depreciable electric utility plant. + References No definition available. + Details
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- Details
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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
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- Definition Period end amount of total gross PPE. + References No definition available. + Details
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- Definition The present value amount of future cost recoveries that are probable and estimable related to plant abandonment's for regulated industries. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 35 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6500292&loc=d3e45591-110387 + Details
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