Derivative Financial Instruments (Schedule of Derivatives Instruments Statements of Financial Position) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Designated as hedging instrument
Amount of gain (loss) recognized in income on related hedged items	$ (561)	$ (781)	$ (2,197)
Designated as hedging instrument | Commodity contract | Futures | Cost of goods sold
Amount of gain (loss) recognized in income on derivatives	(2,004)	(801)	4,920
Designated as hedging instrument | Commodity contract | Firm commitments | Futures | Cost of goods sold
Amount of gain (loss) recognized in income on related hedged items	(79)	(1,613)	582
Designated as hedging instrument | Commodity contract | Inventory | Futures | Cost of goods sold
Amount of gain (loss) recognized in income on related hedged items	(482)	832	(2,779)
Not designated as hedging instrument | Commodity contract | Futures | Cost of goods sold
Amount of gain (loss) recognized in income on derivatives	$ (17,368)	$ 704	$ 19,830