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Fair Value (Reconciliation For All Assets And Liabilities Measured At Fair Value On A Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning Balance | $ (16,428) | $ (19,410)
Included in regulatory assets/liabilities | (1,660) | (2,671)
Settlements | 5,115 | 3,118
Ending Balance | (12,973) | (18,963)
Natural Gas Exchange Agreements [Member] |  |
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning Balance | (3,164) | (5,885)
Included in regulatory assets/liabilities | 203 | 2,012
Settlements | 156 | (405)
Ending Balance | (2,805) | (4,278)
Power Option Agreement [Member] |  |
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning Balance | (19) | (76)
Included in regulatory assets/liabilities | 14 | (190)
Settlements | 0 | 0
Ending Balance | (5) | (266)
Power Exchange Agreements [Member] |  |
Fair Value Liabilities Measured On Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Beginning Balance | (13,245) | (13,449)
Included in regulatory assets/liabilities | (1,877) | (4,493)
Settlements | 4,959 | 3,523
Ending Balance | $ (10,163) | $ (14,419)

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- Definition Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Realized And Unrealized Gains Losses Included In Regulatory Assets + References No definition available. + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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