Accounting For Suspended Exploratory Well Costs (Schedule Of Number Of Projects With Suspended Exploratory Well Costs) (Details) - Projects	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting For Suspended Exploratory Well Costs [Abstract]
Number of projects that only have exploratory well costs capitalized for a period of one year or less	6	11	2
Number of projects that have exploratory well costs capitalized for a period of greater than one year	52	46	58
Total	58	57	60

The number of projects for which exploratory well costs have been capitalized for a period of greater than one year after the completion of drilling.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 1B
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=68064819&loc=SL6806780-109447

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant