Fair Value Measurements (Fair Value Hierarchy Table) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Oil derivative contracts - current assets	$ 26,778	$ 11,936
Oil derivative contracts - noncurrent assets	1,147	0
Total Assets	27,925	11,936
Oil derivative contracts - current liabilities	(5,739)	(8,346)
Oil derivative contracts - noncurrent liabilities	(584)	0
Total Liabilities	(6,323)	(8,346)
Quoted Prices in Active Markets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Oil derivative contracts - current assets	0	0
Oil derivative contracts - noncurrent assets	0
Total Assets	0	0
Oil derivative contracts - current liabilities	0	0
Oil derivative contracts - noncurrent liabilities	0
Total Liabilities	0	0
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Oil derivative contracts - current assets	26,778	8,503
Oil derivative contracts - noncurrent assets	1,147
Total Assets	27,925	8,503
Oil derivative contracts - current liabilities	(5,739)	(6,522)
Oil derivative contracts - noncurrent liabilities	(584)
Total Liabilities	(6,323)	(6,522)
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Oil derivative contracts - current assets	0	3,433
Oil derivative contracts - noncurrent assets	0
Total Assets	0	3,433
Oil derivative contracts - current liabilities	0	(1,824)
Oil derivative contracts - noncurrent liabilities	0
Total Liabilities	$ 0	$ (1,824)

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