Quarterly report pursuant to Section 13 or 15(d)

Oil and Gas Activities (Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities) (Details)

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Oil and Gas Activities (Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities) (Details) (USD $)
 3 Months Ended 6 Months Ended 12 Months Ended
Dec. 31, 2012
Sep. 30, 2012
Dec. 31, 2011
Dec. 31, 2012
Dec. 31, 2011
Jun. 30, 2012
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]            
Proved       $ 27,869,000   $ 28,187,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment, Period Increase (Decrease)       (5,669,000)   (5,740,000)
Unproved       6,620,000   7,091,000
Exploration Costs       4,210,000   3,744,000
Impairment of Oil and Gas Properties 0 900,000 0 890,000 0  
Other Asset Impairment Charges 0          
United States
            
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]            
Proved       24,343,000   24,207,000
Unproved       229,000   104,000
Exploration Costs       2,166,000   1,718,000
Australia
            
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]            
Proved       9,195,000   9,720,000
Unproved       4,459,000   4,389,000
Exploration Costs       0   0
United Kingdom
            
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]            
Proved       0   0
Unproved       1,932,000   2,598,000
Exploration Costs       $ 2,044,000   $ 2,026,000