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Financial Instruments and Risk Management (Tables) | 12 Months Ended
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Dec. 31, 2017
Financial Instruments and Risk Management [Abstract] |
Fair Value of Derivative Instruments Not Designated as Hedging Instruments |
﻿ |  |  |  |  |  |  |  |
﻿ |  |  |  |  |  |  |  |
﻿ |  | December 31, 2017 |  | December 31, 2016
﻿(Thousands of dollars) |  | Asset (Liability) Derivatives |  | Asset (Liability) Derivatives
﻿Type of Derivative Contract |  | Balance Sheet Location |  | Fair Value |  | Balance Sheet Location |  | Fair Value
﻿Commodity |  | Accounts payable | $ | (39,093) |  | Accounts payable | $ | (48,864)
﻿Foreign exchange |  | – |  | – |  | Accounts payable | $ | (73)
﻿
Recognized Gains and Losses for Derivative Instruments Not Designated as Hedging Instruments |
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﻿ |  |  |  | Gain (Loss)
﻿(Thousands of dollars) |  |  |  |  | Year Ended December 31,
﻿Type of Derivative Contract |  | Statement of Operations Locations |  | 2017 |  | 2016
﻿Commodity |  | Sales and other operating revenues |  | $ | 9,567 |  | $ | (63,412)
﻿Foreign exchange |  | Interest and other income (loss) |  |  | – |  |  | 26,714
﻿ |  |  |  | $ | 9,567 |  | $ | (36,698)
﻿

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- Definition Tabular disclosure of the location and amount of derivative instruments and nonderivative instruments designated as hedging instruments reported before netting adjustments, and the amount of gain (loss) on derivative instruments and nonderivative instruments designated and qualified as hedging instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959 + Details
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- Definition Tabular disclosure of the location and fair value amounts of derivative instruments (and nonderivative instruments that are designated and qualify as hedging instruments) reported in the statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959 + Details
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