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, 2012
Jun. 30, 2011
Jun. 30, 2010
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]      
Discount Rate 10.00%    
Future Cash Inflows $ 809,701 $ 735,564 $ 630,873
Future Production Costs (325,941) (303,705) (253,205)
Future Development Costs (38,523) (28,849) (29,073)
Future Income Tax Expense (155,981) (155,701) (133,140)
Future Net Cash Flows 289,256 247,309 215,455
10% annual discount (159,181) (137,029) (130,101)
Standardized measure of discounted future net cash flows 130,075 110,280 85,354
United States
      
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]      
Future Cash Inflows 756,405 734,592 627,842
Future Production Costs (291,212) (303,005) (251,335)
Future Development Costs (34,416) (28,849) (27,293)
Future Income Tax Expense (152,314) (155,701) (132,843)
Future Net Cash Flows 278,463 247,037 216,371
10% annual discount (156,967) (137,021) (131,163)
Standardized measure of discounted future net cash flows 121,496 110,016 85,208
Australia
      
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]      
Future Cash Inflows 53,296 972 3,031
Future Production Costs (34,729) (700) (1,870)
Future Development Costs (4,107) 0 (1,780)
Future Income Tax Expense (3,667) 0 (297)
Future Net Cash Flows 10,793 272 (916)
10% annual discount (2,214) (8) 1,062
Standardized measure of discounted future net cash flows $ 8,579 $ 264 $ 146