Fair Value Measurements (Estimated Fair Values Of Debt Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Level 1 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	$ 7,412	$ 0
Financial Liabilities Fair Value Disclosure	0	2,578
Level 2 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	30,232	17,588
Financial Liabilities Fair Value Disclosure	32,932	11,637
Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	37,644	17,588
Financial Liabilities Fair Value Disclosure	32,932	14,215
Nymex Futures Contracts [Member] | Level 1 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	7,412
Financial Liabilities Fair Value Disclosure		2,578
Nymex Futures Contracts [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	7,412
Financial Liabilities Fair Value Disclosure		2,578
Foreign Exchange Forward [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure		13,455
Financial Liabilities Fair Value Disclosure	12,009	6,722
Foreign Exchange Forward [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure		13,455
Financial Liabilities Fair Value Disclosure	12,009	6,722
Commodity Contract [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	4,564
Financial Liabilities Fair Value Disclosure	3,757	1,230
Commodity Contract [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	4,564
Financial Liabilities Fair Value Disclosure	3,757	1,230
Forward Contracts [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	25,668	4,133
Financial Liabilities Fair Value Disclosure		3,685
Forward Contracts [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Assets Fair Value Disclosure	25,668	4,133
Financial Liabilities Fair Value Disclosure		$ 3,685
Renewable Energy Program [Member] | Level 2 [Member]
Debt Instrument [Line Items]
Financial Liabilities Fair Value Disclosure	17,166
Renewable Energy Program [Member] | Reported Value Measurement [Member]
Debt Instrument [Line Items]
Financial Liabilities Fair Value Disclosure	$ 17,166