Supplemental Oil And Gas Information (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) item $ / bbl	Dec. 31, 2019 item $ / bbl	Dec. 31, 2018 item $ / bbl
Oil And Gas, Average Sale Price And Production Cost Per Unit [Line Items]
Proved undeveloped reserve locations | item	0	0	7
Depreciation, depletion, or any indirect cost | $	$ 0
Barrel Of Oil [Member]
Oil And Gas, Average Sale Price And Production Cost Per Unit [Line Items]
Price | $ / bbl	34.87	50.65	60.21