Derivative And Financial Instruments (Changes In Fair Value) (Details) - Commodity Contract $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) item	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Derivative Instruments Gain Loss [Line Items]
Beginning fair value of commodity derivatives	$ (759)	$ 3,914	$ 3,914
Net gain (loss) on derivatives	4,948	(4,524)
Ending fair value of commodity derivatives	$ 3,714		(759)
Number of counterparties | item	3
Oil reserves
Derivative Instruments Gain Loss [Line Items]
Net gain (loss) on derivatives	$ 4,826	(4,484)	(4,031)
Net settlements received on derivative contracts	(381)		(807)
Natural gas
Derivative Instruments Gain Loss [Line Items]
Net gain (loss) on derivatives	122	$ (40)	259
Net settlements received on derivative contracts	$ (94)		$ (94)