Exploratory Well Costs (Details) (USD $)	6 Months Ended
	Jun. 30, 2011
Notes To Financial Statements [Abstract]
Balance at December 31, 2010	$ 99,801,000
Additions Pending the Determination of Proved Reserves	21,923,000
Reclassifications to Proved Properties	(28,294,000)
Charged to Dry Hole Costs	(19,444,000)
Foreign Currency Translations	1,245,000
Balance at June 30, 2011	75,231,000
Capitalized exploratory well costs that have been capitalized for a period less than one year	10,945,000
Capitalized exploratory well costs that have been capitalized for a period greater than one year	64,286,000
Total	75,231,000
Number of exploratory wells that have been capitalized for a period greater than one year	4
Number of exploratory wells related to a project in the Sichuan Basin, China	1
Number of exploratory wells related to an outside operated, offshore central North Sea project in the United Kingdom	1
Number of exploratory wells related to an East Irish Sea Project in the United Kingdom	1
Number of exploratory wells related to a shale project in British Columbia, Canada	1
Suspended well costs related to a project in the Sichuan Basin, China	27,000,000
Suspended well costs related to an outside operated, offshore Central North Sea project in the United Kingdom	22,000,000
Suspended well costs related to an East Irish Sea project in the United Kingdom	9,000,000
Suspended well costs related to a shale project in British Columbia, Canada	$ 6,000,000
Number of additional wells drilled to evaluate British Columbia shale project	4