Derivative Financial Instruments (Schedule of Derivatives Instruments Statements of Financial Position) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Designated as hedging instrument
Amount of gain (loss) recognized in income on related hedged items	$ (781)	$ (2,197)	$ 4,822
Designated as hedging instrument | Commodity contract | Futures | Cost of goods sold
Amount of gain (loss) recognized in income on derivatives	(801)	4,920	5,763
Designated as hedging instrument | Commodity contract | Firm commitments | Futures | Cost of goods sold
Amount of gain (loss) recognized in income on related hedged items	(1,613)	582	1,814
Designated as hedging instrument | Commodity contract | Inventory | Futures | Cost of goods sold
Amount of gain (loss) recognized in income on related hedged items	832	(2,779)	3,008
Not designated as hedging instrument | Commodity contract | Futures | Cost of goods sold
Amount of gain (loss) recognized in income on derivatives	$ 704	$ 19,830	$ (18,784)