Divestitures and Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ (381)	$ 1,000	$ 14,074	$ 4,323
Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Oil and Gas Sales Revenue	0	6,453	4,456	11,969
Other Operating Income Discontuined Operations	0	26	34	69
Revenues	0	6,479	4,490	12,038
Disposal Group, Including Discontinued Operation, Operating Expense	0	2,779	1,668	5,478
Exploration expense	0	6	0	35
Depreciation and Amortization, Discontinued Operations	0	2,082	0	3,454
Discontinued Operation, Gain (Loss) from Disposal of Discontinued Operation, before Income Tax	415	0	(19,920)	(3,854)
Disposal Group Total Operating Expense	415	4,867	(18,252)	5,113
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax	(415)	1,612	22,742	6,925
Income Tax Expense (Benefit)	(34)	612	8,668	2,602
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	$ (381)	$ 1,000	$ 14,074	$ 4,323