Supplemental Oil and Gas Disclosures (Unaudited) (Schedule of Prices Used for Standardized Measure of Discounted Future Cash Flows Relating to Proved Reserves Disclosure) (Details)	12 Months Ended
	Dec. 31, 2020 $ / bbl $ / MMBTU	Dec. 31, 2019 $ / bbl $ / MMBTU	Dec. 31, 2018 $ / bbl $ / MMBTU
Natural Gas
Reserve Quantities [Line Items]
Average sales price ($ per unit) | $ / MMBTU	1.98	2.58	3.10
Oil
Reserve Quantities [Line Items]
Average sales price ($ per unit)	39.57	55.69	65.56
NGL
Reserve Quantities [Line Items]
Average sales price ($ per unit)	10.27	11.58	17.64