Major Customers (Consolidated Oil, NGL And Gas Revenues) (Details) - Customer concentration	12 Months Ended
Dec. 31, 2019 Rate	Dec. 31, 2018 Rate	Dec. 31, 2017 Rate
Sunoco Logistics Partners L.P.
Concentration Risk [Line Items]
Concentration risk percent	33.00%	28.00%	21.00%
Occidental Energy Marketing Inc.
Concentration Risk [Line Items]
Concentration risk percent	20.00%	17.00%	16.00%
Plains Marketing L.P.
Concentration Risk [Line Items]
Concentration risk percent	13.00%	15.00%	14.00%
Enterprise Products Partners L.P.
Concentration Risk [Line Items]
Concentration risk percent	1.00%	6.00%	11.00%

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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