Annual report pursuant to Section 13 and 15(d)

Oil and Gas Activities (Unaudited) - Net Changes in Capitalized Costs That Are Not Being Depleted Pending Determination of Proved Reserves (Details)

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Oil and Gas Activities (Unaudited) - Net Changes in Capitalized Costs That Are Not Being Depleted Pending Determination of Proved Reserves (Details) - USD ($)
$ in Thousands
 12 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Capitalized Costs of Unproved Properties Excluded from Amortization [Roll Forward]    
Fiscal year beginning balance $ 20,369 $ 21,845
Additions to capitalized costs 361 8,321
Assets sold or held for sale (16,773) (680)
Reclassified to producing properties 0 (8,973)
Charged to expense (3) (3,429) (20)
Exchange adjustment (159) (124)
Fiscal year closing balance 369 20,369
United States    
Capitalized Costs of Unproved Properties Excluded from Amortization [Roll Forward]    
Fiscal year beginning balance 19,029 19,955
Additions to capitalized costs 361 8,047
Assets sold or held for sale (15,961) 0
Reclassified to producing properties 0 (8,973)
Charged to expense (3) (3,429) 0
Exchange adjustment 0 0
Fiscal year closing balance 0 19,029
Australia    
Capitalized Costs of Unproved Properties Excluded from Amortization [Roll Forward]    
Fiscal year beginning balance 0 0
Additions to capitalized costs 0 0
Assets sold or held for sale 0 0
Reclassified to producing properties 0 0
Charged to expense (3) 0 0
Exchange adjustment 0 0
Fiscal year closing balance 0 0
United Kingdom    
Capitalized Costs of Unproved Properties Excluded from Amortization [Roll Forward]    
Fiscal year beginning balance 1,340 1,890
Additions to capitalized costs 0 274
Assets sold or held for sale (812) (680)
Reclassified to producing properties 0 0
Charged to expense (3) 0 (20)
Exchange adjustment (159) (124)
Fiscal year closing balance $ 369 $ 1,340