Derivative Financial Instruments (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Gains or losses on derivative instruments, statement of income
Ineffectiveness - amount of gain (loss) recognized in income on related hedged items	$ 2,400	$ 1,200,000	$ 59,000	$ 32,000
Gain (loss) excluded from hedge effectiveness testing	(1,200,000)	1,700,000	205,000	(519,000)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	480,000	88,000	491,000	147,000
Net gains (loss) reclassified	236,000	$ 157,000	198,000	$ 440,000
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months	284,000		$ 284,000
Period Within Which The Company Expects To Reclassify Net Gains On Derivative Instruments From A O C I to Earnings			12 months
Futures | Commodity contract | Other current assets
Commodity contract commitments
Fair value of derivatives including required margin deposits	$ 3,100,000		$ 3,100,000		$ 3,700,000