Summary of Significant Accounting Policies (Details) (USD $)	1 Months Ended		3 Months Ended		49 Months Ended
	Nov. 30, 2012	Oct. 31, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Jun. 30, 2012	Jun. 30, 2011
Significant Accounting Policies [Line Items]
Results of Operations, Dry Hole Costs	$ 4,300,000	$ 33,900,000	$ 43,700,000
Impairment of Ongoing Project			8,400,000
Cash and cash equivalents			137,784,000	137,448,000	137,784,000	129,983,000	150,007,000
Impairment charges, unproved properties			8,410,000	0
Equity Method Investment, Ownership Percentage			37.00%		37.00%	45.00%
Stock options, net-settled					45,000
Equity Method Investments			33,800,000		33,800,000
Exploration Expense			44,984,000	24,000
Moblize, Inc. [Member]
Significant Accounting Policies [Line Items]
Cost method investment ownership percentage			19.50%		19.50%
Exaro Energy III LLC [Member]
Significant Accounting Policies [Line Items]
Future Investment In Affiliates			15,000,000
Cash Considerration in Exchange for Assignment of Rights to Assets and Liabilities			7,500,000		7,500,000
Acquisition Of Commitment By Another Party			7,500,000
Republic Exploration LLC [Member]
Significant Accounting Policies [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest			32.30%
Alta Energy [Member]
Significant Accounting Policies [Line Items]
Percentage Investment in Project			2.00%		2.00%
Kaybob Duvernay [Member]
Significant Accounting Policies [Line Items]
Percentage Investment in Project			5.00%		5.00%
Ship Shoal 263 [Member]
Significant Accounting Policies [Line Items]
Impairment of Ongoing Project			6,300,000
Eugene Island 24 [Member]
Significant Accounting Policies [Line Items]
Impairment of Ongoing Project			2,100,000
Ship Shoal 134 and South Timbalier 75 [Member]
Significant Accounting Policies [Line Items]
Impairment of Ongoing Project			6,600,000
Jim Hogg County, Texas [Member]
Significant Accounting Policies [Line Items]
Impairment of Ongoing Project			$ 1,200,000