Concentration Of Market And Credit Risk (Schedule Of Revenue By Major Customers) (Details) (USD $) In Thousands	12 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Kosmos Energy Ghana Inc. [Member]
Revenues from significant customers	$ 136,205	$ 90,936
Sarawak Shell Bhd. [Member]
Revenues from significant customers	138,836	84,617	81,538
Chevron Australia [Member]
Revenues from significant customers	199,685	81,577
Noble Energy Mediterranean, Ltd. [Member]
Revenues from significant customers			149,603
Woodside Energy Ltd. [Member]
Revenues from significant customers			$ 114,637

Amount of revenue from external customers for the reportable segment. Such disclosure is presented if the amount is: (a) included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 131

-Paragraph 27

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Name:	us-gaap_RevenuesFromExternalCustomers
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration