Derivative And Financial Instruments (Effect On Statement Of Operations) (Details) - Commodity Contract - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Embedded Derivative [Line Items]
Net gain (loss) on derivatives	$ 4,948	$ (4,524)
Oil reserves
Embedded Derivative [Line Items]
Net gain (loss) on derivatives	4,826	(4,484)	$ (4,031)
Natural gas
Embedded Derivative [Line Items]
Net gain (loss) on derivatives	$ 122	$ (40)	$ 259