Assets Held for Sale (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2013	Dec. 31, 2012
Assets held for sale [Abstract]
Assets Held-for-sale Reasonably Certain Period for Sale	1
Asset retirement obligation associated with oil and gas properties held for sale	$ 4,617	$ 1,393
Oil and gas properties held for sale net of accumulated depletion, depreciation and amortization of $55,348 in 2013 and 20,676 in 2012	$ 87,310	$ 33,620

Long-lived assets that are held for sale apart from normal operations and anticipated to be sold in less than one year.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1107-107759

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 144

-Paragraph 46

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_AssetsHeldForSaleLongLived
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant