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Commitments and Contingencies, Variable Interest Entities (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 USD ($) MW | Dec. 31, 2017 USD ($) MW
Independent Power Producing Entities |  |
Purchased Power Agreements [Abstract] |  |
Generating capacity (in MW) | MW | 3,770 | 3,537
VIE Purchase Power Agreement Expiration Date | 2041 |
Harrington Station Power Plant [Member] |  |
Fuel Contracts [Abstract] |  |
Coal Supply Agreement Expiration Date | 2022 |
Tolk Station Power Plant [Member] |  |
Fuel Contracts [Abstract] |  |
Coal Supply Agreement Expiration Date | 2022 |
Low-Income Housing Limited Partnerships |  |
Amount Reflected in Consolidated Balance Sheets [Abstract] |  |
Current assets | $ 5 | $ 6
Property, plant and equipment, net | 42 | 46
Other noncurrent assets | 1 | 1
Total assets | 48 | 53
Current liabilities | 7 | 9
Mortgages and other long-term debt payable | 26 | 26
Other noncurrent liabilities | 0 | 1
Total liabilities | $ 33 | $ 36

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- Definition The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=108788376&loc=d3e5710-111685 + Details
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- Definition Fuel Contracts [Abstract] + References No definition available. + Details
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- Definition Generating capacity under long-term purchased power agreements. + References No definition available. + Details
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Period Type: | instant

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- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
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- Definition The maximum duration of purchase power agreements currently under contract in which the supplying entity represents a non-consolidating VIE. + References No definition available. + Details
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- Definition The carrying amount of the consolidated Variable Interest Entity's mortgages and other long-term debt payable included in the reporting entity's statement of financial position. + References No definition available. + Details
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