Divestitures and Assets Held for Sale (Details) (USD $)	3 Months Ended
Mar. 31, 2012	Dec. 31, 2011	Apr. 27, 2012 Assets Held-for-sale [Member]
Assets Held for Sale
Reasonably certain period within which sale will take place (in years)	1
Book value of assets held for sale, net of accumulated depletion, depreciation and amortization	$ 42,200,000
Asset retirement obligation associated with oil and gas properties held for sale (note 3)	1,770,000	1,277,000
Assets Held-for-sale, Long Lived			$ 54,600,000

Represents the sum of the carrying value of all the Assets Held-for-Sale at the balance sheet date.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 144

-Paragraph 47

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

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