Exploratory Costs (Capitalized Exploratory Costs And The Number Of Projects For Which Exploratory Costs Have Been Capitalized) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010
Exploratory Costs
One year or less	$ 77,129		$ 70,635
More than one year	7,982		25,558
Capitalized exploratory costs, total	$ 85,111	$ 80,530	$ 96,193
Number of projects with exploratory costs that have been suspended for a period greater than one year	1		3

The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS19-1
-Paragraph 10
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6821537&loc=SL6806780-109447

Name:	us-gaap_CapitalizedExploratoryWellCosts
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant