Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Schedule of Fair Value of Financial Instruments (Details)

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Summary of Significant Accounting Policies - Schedule of Fair Value of Financial Instruments (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Fair Value of Marketable Securities $ 18,765
Level 1 [Member]    
Fair Value of Marketable Securities  
Level 2 [Member]    
Fair Value of Marketable Securities 18,765  
Level 3 [Member]    
Fair Value of Marketable Securities  
U.S. Government Obligations [Member]    
Fair Value of Marketable Securities 1,744  
U.S. Government Obligations [Member] | Level 1 [Member]    
Fair Value of Marketable Securities  
U.S. Government Obligations [Member] | Level 2 [Member]    
Fair Value of Marketable Securities 1,744  
U.S. Government Obligations [Member] | Level 3 [Member]    
Fair Value of Marketable Securities  
Corporate Obligations [Member]    
Fair Value of Marketable Securities 17,021  
Corporate Obligations [Member] | Level 1 [Member]    
Fair Value of Marketable Securities  
Corporate Obligations [Member] | Level 2 [Member]    
Fair Value of Marketable Securities 17,021  
Corporate Obligations [Member] | Level 3 [Member]    
Fair Value of Marketable Securities