Investment In Oil and Gas Properties (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investment in Oil and Gas Properties (Textual) [Abstract]
Write-down of oil and gas properties				$ 508,989
United States [Member]
Investment in Oil and Gas Properties (Textual) [Abstract]
Asset retirement costs included in development cost		96,386	56,444	78,387
Write-down of oil and gas properties	343,932			508,989
Oil average sales price (per barrel)				58.95
Natural gas average price (per Mcf)				3.49
Benefit of hedges reduced the write-down				94,541
Henry hub gas price (per MMBtu)	3.62
West Texas intermediate oil price (per barrel)	45.64
China [Member]
Investment in Oil and Gas Properties (Textual) [Abstract]
Specifically identified drilling projects		80
Projects expected to be evaluated		4 years
Interest costs capitalized on unevaluated properties		$ 42,033	$ 30,783	$ 23,943