Organization and Summary of Significant Accounting Policies (Narrative) (Details) $ / shares in Units, $ in Thousands			3 Months Ended		12 Months Ended
	Jun. 03, 2014 $ / shares	Jan. 15, 2014 USD ($) item	Sep. 30, 2014 USD ($) agreement $ / shares	Sep. 30, 2013 USD ($)	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 $ / shares	Dec. 31, 2014 $ / shares	Jun. 30, 2014 USD ($) $ / shares	Jun. 01, 2014 USD ($)	Sep. 26, 2013 USD ($)	Sep. 01, 2013 USD ($)	Apr. 02, 2013 USD ($)	Jan. 01, 2013 USD ($)	Oct. 25, 2012 USD ($)
Business Acquisition [Line Items]
Common stock, par value | $ / shares	$ 0.001		$ 0.001		$ 0.001	$ 0.001	$ 0.001	$ 0.001
Aggregate consideration to be paid in acquirer stock	35.00%
Aggregate consideration paid in cash	65.00%
Number of Leases bid upon | agreement			4
Accrued exploration costs, development costs and lease operating Costs					$ 50,900			$ 127,600
Other accrued expenses					19,200			18,100
Accrued interest included in purchase price					$ 25,900			$ 15,800
Costs associated with unevaluated properties are transferred to evaluated properties period					4 years
Proceeds from sale of oil and gas properties					$ 21,000
Capitalized general and administrative expense					15,500
Valuation allowance					$ 189,604
Goodwill impairment			$ 329,293	$ 12
Nexen Acquisition [Member]
Business Acquisition [Line Items]
Purchase price											$ 64,732
Acquired certain interests in producing oil and natural gas assets		$ 70,400
Number of Leases bid upon | item		5
Percentage of working interest acquired		100.00%
West Delta 29 Acquisition [Member]
Business Acquisition [Line Items]
Purchase price										$ 21,800			$ 15,146
Sale of non-operated Bay Marchand field										$ 16,500
The South Pass 49 [Member]
Business Acquisition [Line Items]
Purchase price									$ 230,185
Senior Notes Due 2018 [Member] | Hilcorp Acquisition [Member]
Business Acquisition [Line Items]
Accrued interest included in purchase price														$ 4,800
Energy XXI (Bermuda) Limited [Member]
Business Acquisition [Line Items]
Common stock, par value | $ / shares	$ 0.005
Minimum [Member]
Business Acquisition [Line Items]
Other property, plant and equipment, useful lives					3 years
Maximum [Member]
Business Acquisition [Line Items]
Other property, plant and equipment, useful lives					5 years
Non-Operated Bay Marchand Asset [Member]
Business Acquisition [Line Items]
Sale of non-operated Bay Marchand field												$ 62,800