Basis of Presentation - Goodwill Roll-Forward (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Jun. 30, 2012 reporting_unit	Jun. 30, 2012 Magellan Petroleum Australia Limited (MPAL)	Jun. 30, 2011 Magellan Petroleum Australia Limited (MPAL)	Jun. 30, 2012 Nautilus Poplar, LLC (NP)	Jun. 30, 2011 Nautilus Poplar, LLC (NP)
Goodwill [Line Items]
Goodwill, Number of Reporting Units	2
Goodwill [Roll Forward]
Fiscal year ended June 30, 2011	$ 4,695	$ 1,500	$ 4,000	$ 700	$ 700
Fiscal year ended June 30, 2012	$ 2,174	$ 1,500	$ 4,000	$ 700	$ 700

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

+ Details