Derivative Financial Instruments (Schedule of Derivatives Instruments Statements of Financial Position) (Details) - Commodity contract - Futures - Cost of goods sold - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Designated as hedging instrument
Amount of gain (loss) recognized in income on derivatives	$ 302	$ (8,943)	$ (560)	$ 1,113
Amount of gain (loss) recognized in income on related hedged items	(701)	6,864	(358)	59
Designated as hedging instrument | Firm commitments
Amount of gain (loss) recognized in income on related hedged items	(519)	5,111	(603)	1,718
Designated as hedging instrument | Inventory
Amount of gain (loss) recognized in income on related hedged items	(182)	1,753	245	(1,659)
Not designated as hedging instrument
Amount of gain (loss) recognized in income on derivatives	$ 4,536	$ 13,803	$ 5,946	$ 19,523