Major Customers (Consolidated Oil, NGL And Gas Revenues) (Details) - Customer concentration	12 Months Ended
Dec. 31, 2020 Rate	Dec. 31, 2019 Rate	Dec. 31, 2018 Rate
Sunoco Logistics Partners L.P.
Concentration Risk [Line Items]
Concentration risk percent	36.00%	33.00%	28.00%
Occidental Energy Marketing Inc.
Concentration Risk [Line Items]
Concentration risk percent	18.00%	20.00%	17.00%
Plains Marketing L.P.
Concentration Risk [Line Items]
Concentration risk percent	14.00%	13.00%	15.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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