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Commitments And Contingencies (Narrative) (Details) $ in Millions | 9 Months Ended
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Sep. 30, 2018 USD ($)
Commitments and Contingencies [Line Items] |  |
Minimum future commitments | $ 2,222 |
Present value abandonment obligation | 36 |
IPL [Member] |  |
Commitments and Contingencies [Line Items] |  |
Minimum future commitments | 1,565 |
Indemnification obligations, maximum | 17 |
WPL [Member] |  |
Commitments and Contingencies [Line Items] |  |
Minimum future commitments | 643 |
Capital Purchase Obligation [Member] |  |
Commitments and Contingencies [Line Items] |  |
Minimum future commitments | 82 |
Capital Purchase Obligation [Member] | IPL [Member] |  |
Commitments and Contingencies [Line Items] |  |
Minimum future commitments | 26 |
Capital Purchase Obligation [Member] | WPL [Member] |  |
Commitments and Contingencies [Line Items] |  |
Minimum future commitments | 56 |
Purchased Power [Member] |  |
Commitments and Contingencies [Line Items] |  |
Minimum future commitments | 1,089 | [1]
Purchased Power [Member] | IPL [Member] |  |
Commitments and Contingencies [Line Items] |  |
Minimum future commitments | 1,063 | [1]
Purchased Power [Member] | WPL [Member] |  |
Commitments and Contingencies [Line Items] |  |
Minimum future commitments | 26 | [1]
Indemnification Agreement [Member] |  |
Commitments and Contingencies [Line Items] |  |
Indemnification obligations, maximum | 90 |
Indemnification Agreement [Member] | Purchased Power [Member] |  |
Commitments and Contingencies [Line Items] |  |
Indemnification obligations, maximum | $ 17 |
[1] | Includes payments required by PPAs for capacity rights and minimum quantities of MWhs required to be purchased. Alliant Energy’s and IPL’s amounts include minimum future commitments related to IPL’s purchase of capacity and the resulting energy from DAEC through December 2025. In July 2018, IPL entered into an amendment to shorten the term of the DAEC PPA by five years in exchange for a $110 million buyout payment by IPL in September 2020, which is not included in Alliant Energy’s and IPL’s amounts. The amendment to the DAEC PPA is contingent upon IUB approval of IPL’s July 2018 application regarding recovery of the buyout payment.

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- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248 + Details
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- Definition The minimum amount the entity agreed to spend under the long-term purchase commitment. + 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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