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Amount of gain (loss)recognized in the income statement from the hedging ineffectiveness of a fair value hedge.

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Derivative Financial Instruments (Narrative) (Details) - Futures - Commodity contract - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Other current assets
Commodity contract commitments
Fair value of derivatives including required margin deposits	$ 6,000		$ 6,000		$ 3,200
Designated as hedging instrument
Gains or losses on derivative instruments, statement of income
Ineffectiveness - amount of gain (loss) recognized in income on related hedged items	(35)	$ (84)	62	$ (175)
Gain (loss) excluded from hedge effectiveness testing	$ 1,100	$ (60)	$ 1,700	$ (125)