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Related Parties (Service Agreements) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014
Corporate Services Billings [Member] | IPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | $ 38 | $ 37 | $ 114 | $ 111
Corporate Services Billings [Member] | WPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | 30 | 30 | 90 | 89
Sales Credited [Member] | IPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | 2 | 2 | 8 | 6
Sales Credited [Member] | WPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | 9 | 2 | 21 | 4
Purchases Billed [Member] | IPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | 110 | 106 | 278 | 313
Purchases Billed [Member] | WPL [Member] |  |  |  |
Related Party Transactions [Line Items] |  |  |  |
Amounts billed between related parties | $ 16 | $ 34 | $ 49 | $ 92

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- Definition Amount of transactions with related party during the financial reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864 + 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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- Details
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- Details
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- Details
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