Suspended Exploratory Well Costs (Detalis 1) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Aging of capitalized exploratory well costs that have been suspended for more than one year
Capitalized exploratory well costs that have been capitalized for more than one year	$ 15,028	$ 10,727
Exploratory Well Costs Capitalized In Year 2011 [Member]
Aging of capitalized exploratory well costs that have been suspended for more than one year
Capitalized exploratory well costs that have been capitalized for more than one year	494
Exploratory Well Costs Capitalized in Year 2010 [Member]
Aging of capitalized exploratory well costs that have been suspended for more than one year
Capitalized exploratory well costs that have been capitalized for more than one year	10,127
Exploratory Well Costs Capitalized in Year 2009 [Member]
Aging of capitalized exploratory well costs that have been suspended for more than one year
Capitalized exploratory well costs that have been capitalized for more than one year	2,884
Exploratory Well Costs Capitalized in Year 2008 [Member]
Aging of capitalized exploratory well costs that have been suspended for more than one year
Capitalized exploratory well costs that have been capitalized for more than one year	$ 1,523