Exploratory Well Costs (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Notes To Financial Statements [Abstract]
Balance at January 1	$ 99,801,000	$ 118,459,000	$ 85,255,000
Additions Pending the Determination of Proved Reserves	31,271,000	94,090,000	75,362,000
Reclassifications to Proved Properties	(29,227,000)	(93,333,000)	(40,614,000)
Charged to Dry Hole Costs	(42,178,000)	(20,267,000)	(11,223,000)
Foreign Currency Translations	1,444,000	852,000	9,679,000
Balance at December 31	61,111,000	99,801,000	118,459,000
Capitalized exploratory well costs that have been capitalized for a period less than one year	17,009,000	43,408,000	51,141,000
Capitalized exploratory well costs that have been capitalized for a period greater than one year	44,102,000	56,393,000	67,318,000
Number of suspended wells that have been capitalized for a period greater than one year	4	4	4
Number of suspended wells related to an outside operated, offshore Central North Sea project in the United Kingdom	1	1	1
Number of suspended wells related to an East Irish Sea Project in the United Kingdom	1	1
Number of suspended wells related to a project in the Sichuan Basin, China	1	1
Number of suspended wells related to shale projects in British Columbia	1	1	3
Suspended well costs related to an outside operated, offshore Central North Sea project in the United Kingdom	20,000,000	21,000,000	22,000,000
Suspended well costs related to an East Irish Sea project in the United Kingdom	9,000,000	9,000,000
Suspended well costs related to a project in the Sichuan Basin, Sichuan Province, China	9,000,000	20,000,000
Suspended well costs related to shale projects in British Columbia	$ 6,000,000	$ 6,000,000	$ 45,000,000