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Derivatives And Risk Management (Derivative Instruments Summary) (Details) - USD ($) | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Derivatives, Fair Value [Line Items] |  |
Gross Asset | $ 55,941,000 | $ 51,506,000
Gross Liability | (71,127,000) | (161,467,000)
Collateral Netted | 19,349,000 | 62,408,000
Net Asset (Liability) on Balance Sheet | 4,163,000 | (47,553,000)
Interest Rate Swap [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Collateral Netted | 0 | 34,970,000
Commodity Contracts [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Collateral Netted | 19,349,000 | 27,438,000
Other Current Liabilities [Member] | Interest Rate Swap [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Gross Asset |  | 0
Gross Liability |  | (63,399,000)
Collateral Netted |  | 28,952,000
Net Asset (Liability) on Balance Sheet |  | (34,447,000)
Other Current Liabilities [Member] | Commodity Contracts [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Gross Asset | 29,992,000 | 26,641,000
Gross Liability | (50,107,000) | (52,895,000)
Collateral Netted | 13,262,000 | 17,406,000
Net Asset (Liability) on Balance Sheet | (6,853,000) | (8,848,000)
Other Current Assets [Member] | Foreign Exchange Contract [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Gross Asset | 26,000 | 32,000
Gross Liability | 0 | (1,000)
Collateral Netted | 0 | 0
Net Asset (Liability) on Balance Sheet | 26,000 | 31,000
Other Current Assets [Member] | Interest Rate Swap [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Gross Asset |  | 2,597,000
Gross Liability |  | (270,000)
Collateral Netted |  | 0
Net Asset (Liability) on Balance Sheet |  | 2,327,000
Other Current Assets [Member] | Commodity Contracts [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Gross Asset | 904,000 | 1,386,000
Gross Liability | (27,000) | (122,000)
Collateral Netted | 0 | 0
Net Asset (Liability) on Balance Sheet | 877,000 | 1,264,000
Other Property And Investments Net And Other Non-current Assets [Member] | Interest Rate Swap [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Gross Asset | 18,029,000 | 4,880,000
Gross Liability | 0 | (2,304,000)
Collateral Netted | 0 | 0
Net Asset (Liability) on Balance Sheet | 18,029,000 | 2,576,000
Other Property And Investments Net And Other Non-current Assets [Member] | Commodity Contracts [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Gross Asset | 7,000 |
Gross Liability | 0 |
Collateral Netted | 0 |
Net Asset (Liability) on Balance Sheet | 7,000 |
Other Noncurrent Liabilities [Member] | Interest Rate Swap [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Gross Asset | 129,000 | 0
Gross Liability | (4,577,000) | (7,540,000)
Collateral Netted | 0 | 6,018,000
Net Asset (Liability) on Balance Sheet | (4,448,000) | (1,522,000)
Other Noncurrent Liabilities [Member] | Commodity Contracts [Member] |  |
Derivatives, Fair Value [Line Items] |  |
Gross Asset | 6,854,000 | 15,970,000
Gross Liability | (16,416,000) | (34,936,000)
Collateral Netted | 6,087,000 | 10,032,000
Net Asset (Liability) on Balance Sheet | $ (3,475,000) | $ (8,934,000)

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- Definition Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 + Details
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