Derivative And Financial Instruments (Effect On Statement Of Operations) (Details) - Commodity Contract - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Embedded Derivative [Line Items]
Net gains (losses) on derivatives	$ 1,252	$ (2,431)	$ (2,272)	$ (8,083)
Oil reserves
Embedded Derivative [Line Items]
Net gains (losses) on derivatives	1,195	(2,454)	(2,482)	(8,110)	$ 1,400
Natural gas
Embedded Derivative [Line Items]
Net gains (losses) on derivatives	$ 57	$ 23	$ 210	$ 27	$ (84)