Fair Value Measurements (Estimated Fair Values Of Debt Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Level 1 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	$ 0	$ 0
Financial Liabilities Fair Value Disclosure	6,987	2,578
Level 2 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	15,141	17,588
Financial Liabilities Fair Value Disclosure	11,900	11,637
Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	15,141	17,588
Financial Liabilities Fair Value Disclosure	18,887	14,215
Commodity [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	3,561
Commodity [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	3,561
Nymex Futures Contracts [Member] | Level 1 [Member]
Debt Instrument [Line Items]
Financial Liabilities Fair Value Disclosure	6,987	2,578
Nymex Futures Contracts [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Liabilities Fair Value Disclosure	0
Nymex Futures Contracts [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Liabilities Fair Value Disclosure	6,987	2,578
Foreign Exchange Forward [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	7,361
Financial Liabilities Fair Value Disclosure	395	6,722
Foreign Exchange Forward [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	7,361
Financial Liabilities Fair Value Disclosure	395	6,722
Commodity Contract [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure		13,455
Financial Liabilities Fair Value Disclosure		1,230
Commodity Contract [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure		13,455
Financial Liabilities Fair Value Disclosure		1,230
Forward Contracts [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	4,219	4,133
Financial Liabilities Fair Value Disclosure	6,156	3,685
Forward Contracts [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	4,219	4,133
Financial Liabilities Fair Value Disclosure	6,156	$ 3,685
Renewable Energy Program [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Liabilities Fair Value Disclosure	5,349
Renewable Energy Program [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Liabilities Fair Value Disclosure	$ 5,349