Derivative Financial Instruments - FV Hedges (Details) - Fair Value Hedge - Cost of sales - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Futures contracts
Fair values of derivative financial instruments
Amount of Gain (Loss) Recognized in Income on Derivatives	$ (12,776)	$ (3,930)	$ (22,507)	$ 36,990
Inventories
Fair values of derivative financial instruments
Amount of Gain (Loss) Recognized in Income on Hedged Items	$ 12,786	$ 4,370	$ 24,160	$ (37,412)

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109977999&loc=d3e76258-113986

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- Definition

Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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