Annual report pursuant to Section 13 and 15(d)

Supplemental Oil and Gas Information - Discounted Future Net Cash Flows (Details)

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Supplemental Oil and Gas Information - Discounted Future Net Cash Flows (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]    
Discount Rate 10.00%  
Future cash inflows $ 666,800 $ 809,701
Future production costs (283,279) (325,941)
Future development costs (33,017) (38,523)
Future income tax expense (112,193) (155,981)
Future net cash flows 238,311 289,256
10% annual discount (130,635) (159,181)
Standardized measures of discounted future net cash flows 107,676 130,075
United States
    
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]    
Future cash inflows 610,853 756,405
Future production costs (244,703) (291,212)
Future development costs (28,922) (34,416)
Future income tax expense (112,193) (152,314)
Future net cash flows 225,035 278,463
10% annual discount (127,644) (156,967)
Standardized measures of discounted future net cash flows 97,391 121,496
Australia
    
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]    
Future cash inflows 55,947 53,296
Future production costs (38,576) (34,729)
Future development costs (4,095) (4,107)
Future income tax expense 0 (3,667)
Future net cash flows 13,276 10,793
10% annual discount (2,991) (2,214)
Standardized measures of discounted future net cash flows $ 10,285 $ 8,579