Supplementary Oil And Natural Gas Disclosures (Unaudited) (Results Of Operations For Oil And Gas Producing Activities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Revenues
Sales	$ 54,442	$ 39,410
Production costs	12,293	9,511
Exploration expenses		359
Depreciation, depletion and amortization	11,928	10,057
Income before income taxes	30,221	19,483
Income tax expenses	10,789	7,014
Results of operations from producing activities (excluding corporate overhead)	19,432	12,469
Equity Method Investments [Member]
Revenues
Sales	53,181	56,964
Production costs	22,034	23,375
Exploration expenses		105
Depreciation, depletion and amortization	18,449	18,557
Income before income taxes	12,698	14,927
Income tax expenses	4,533	5,373
Results of operations from producing activities (excluding corporate overhead)	$ 8,165	$ 9,554