Derivative Financial Instruments (Derivatives and Hedging-Fair Value Hedges) (Details) - Commodity Contract [Member] - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Increase (Decrease) in Fair Value of Price Risk Fair Value Hedging Instruments	$ (368)	$ 3,370	$ (549)	$ 6,768
Increase (Decrease) in Fair Value of Hedged Item in Price Risk Fair Value Hedge	$ 368	$ (3,370)	$ 549	$ (6,768)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

Amount of unrealized gain (loss) recognized in earnings related to the fair value of the hedged item in a price risk fair value hedge, offset by the gain (loss) on the hedging instrument to the extent that the fair value hedge is determined to be effective.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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- Definition

Amount of unrealized gain (loss) related to the fair value of price risk derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective.

+ References

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