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Other Long-Term Assets - Additional Information (Detail) - USD ($)
Dec. 31, 2016
Dec. 31, 2015
Other Long Term Assets [Line Items]    
Deposits for conservation and documentation of artifacts $ 100,000  
Deposits 532,500 $ 540,590
UNITED KINGDOM    
Other Long Term Assets [Line Items]    
Deposits with United Kingdom's Ministry of Defense $ 432,500