Quarterly report pursuant to Section 13 or 15(d)

Property, Plant and Equipment - Additional Information (Detail)

v3.7.0.1
Property, Plant and Equipment - Additional Information (Detail)
 1 Months Ended 3 Months Ended 6 Months Ended
Feb. 28, 2017
License
Jun. 30, 2017
USD ($)
Jun. 30, 2016
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2016
USD ($)
Development Expenses [Member]          
Property, Plant and Equipment [Line Items]          
Depreciation expense   $ 79,000 $ 24,000 $ 139,000 $ 24,000
Australia [Member]          
Property, Plant and Equipment [Line Items]          
Reserves   0   0  
Depletion   $ 0   $ 0  
United Kingdom [Member]          
Property, Plant and Equipment [Line Items]          
Number of non-operating interest in licenses | License 2        
United Kingdom [Member] | Non-operating Interest in Licenses One [Member]          
Property, Plant and Equipment [Line Items]          
License expiration date 2021-06        
United Kingdom [Member] | Non-operating Interest in Licenses Two [Member]          
Property, Plant and Equipment [Line Items]          
License expiration date 2021-09