Supplementary Oil And Natural Gas Disclosures (Unaudited) (Standardized Measure Of Discounted Future Cash Flows Relating To Proved Reserves) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Standardized Measure [Abstract]
Future cash inflows	$ 701,170	$ 486,199
Future production costs	(126,627)	(43,392)
Future development and abandonment costs	(58,388)	(86,125)
Future income tax expenses	(185,816)	(129,262)
Future net cash flows	330,339	227,420
10% annual discount for estimated timing of cash flows	92,590	57,928
Standardized measure of discounted future net cash flows	237,749	169,492
Equity Method Investments [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Standardized Measure [Abstract]
Future cash inflows	414,246	356,126
Future production costs	(100,848)	(83,215)
Future development and abandonment costs	(67,760)	(84,260)
Future income tax expenses	(73,202)	(66,161)
Future net cash flows	172,436	122,490
10% annual discount for estimated timing of cash flows	39,704	20,014
Standardized measure of discounted future net cash flows	$ 132,732	$ 102,476