Derivatives (Pre-tax Gains and Losses) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Commodity \| Cost of Sales and Merchandising Revenues
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives instruments recognized in earnings	$ 45,844	$ (41,873)	$ 20,608	$ (14,848)
Not Designated as Hedging Instrument \| Interest rate contracts \| Interest Income (Expense)
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives instruments recognized in earnings	351	(17)	1,141	372
Not Designated as Hedging Instrument \| Foreign currency contract \| Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives instruments recognized in earnings	(413)	669	(1,535)	767
Designated as Hedging Instrument \| Foreign currency contract \| Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives instruments recognized in OCI	$ 67	$ 0	$ 67	$ 0

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: 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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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The effective portion of gains on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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