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Commitments, Guarantees and Contingencies - Power Purchase Agreements (Details) | 7 Months Ended | 9 Months Ended
--- | --- | ---
Dec. 31, 2014 | Sep. 30, 2015 USD ($) MWh Years MW | Sep. 30, 2014 USD ($)
Square Butte PPA [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
PPA Counterparty Debt Outstanding | $ |  | $ 377,900,000 |
Annual Debt Service | $ |  | 45,000,000 |
Power Purchased under Long-term Contracts | $ |  | 57,600,000 | $ 51,800,000
Interest Expense | $ |  | $ 7,600,000 | $ 7,900,000
Square Butte PPA [Member] | Square Butte Coal-fired Unit [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Generating Unit Capacity (MW) |  | 455 |
Output Entitlement |  | 50.00% |
Square Butte PPA [Member] | Minnkota Power Sales Agreement [Member] | Square Butte Coal-fired Unit [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Entitlement | 23.00% | 28.00% |
Minnkota Power PPA [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 50 |
Oliver Wind I PPA [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 50 |
Fixed Capacity Charges | $ |  | $ 0 |
Oliver Wind II PPA [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 48 |
Fixed Capacity Charges | $ |  | $ 0 |
Manitoba Hydro PPA (expires May 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 50 |
Manitoba Hydro PPA (expires April 2022) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MWh) | MWh |  | 1,000,000 |
Manitoba Hydro PPA (expires 2035) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 250 |
Term of Contract (Years) | Years |  | 15 |
Manitoba Hydro PPA (expires 2040) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 133 |
Term of Contract (Years) | Years |  | 20 |
Great River Energy and Capacity PPA (expires May 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 50 |
Great River Capacity Only PPA (expires May 2020) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 50 |
TransAlta Off-Peak Hours PPA (expires 2019) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 50 |
TransAlta On-Peak Hours PPA (expire 2019) [Member] |  |  |
Power Purchase Agreements [Line Items] |  |  |
Output Being Purchased (MW) |  | 100 |

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- Definition Under long-term contracts with public utility districts, cooperatives or other organizations, a utility company receives a portion of the output of a production plant constructed and financed by the district or cooperative. The utility has only a nominal or no investment at all in the plant but pays a proportionate part of the plant's costs, including debt service. If the utility is obligated to pay certain minimum amounts which cover debt service requirements whether or not the plant is operating, the amount can be disclosed here. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 10.D) -URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 10 -Section D + Details
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