Divestitures (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Divestitures [Abstract]
Approximate proceeds received from the sales of producing properties and acreage	$ 450

The value of all consideration given or received by the Entity in the significant acquisition or disposal.

No definition available.

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