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Summary of Significant Accounting Policies (Detail Textuals)
 12 Months Ended
Dec. 31, 2016
USD ($)
Segment
Dec. 31, 2016
GBP (£)
Segment
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Accounting Policies [Line Items]        
Number of operating segments | Segment 1      
Cash and cash equivalents $ 16,520,000   $ 20,440,000 $ 24,189,000
Number of geographic areas for development operations | Segment 2 2    
Cash balances insured by FDIC $ 250,000      
Cash exceeding balance insured by FDIC 15,000,000      
Cash balance insured by FSCS | £   £ 75,000    
Cash exceeding balance insured by FSCS $ 1,100,000      
Impact of change in accounting policy recorded in accumulated deficit     $ 89,000  
Property, plant and equipment | Minimum        
Accounting Policies [Line Items]        
Estimated useful life 3 years      
Property, plant and equipment | Maximum        
Accounting Policies [Line Items]        
Estimated useful life 5 years      
Leasehold improvements | Minimum        
Accounting Policies [Line Items]        
Estimated useful life 5 years      
Leasehold improvements | Maximum        
Accounting Policies [Line Items]        
Estimated useful life 15 years