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Investments Investments (Narrative) (Details) (WPL [Member], ATC [Member]) | Dec. 31, 2013
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WPL [Member] | ATC [Member] |
Schedule of Equity Method Investments [Line Items] |
Ownership interest percentage | 16.00%

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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 + Details
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Balance Type: | na
Period Type: | instant

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- Details
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Balance Type: | na
Period Type: | duration