Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation and Significant Accounting Policies - Additional Information (Details)

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Basis of Presentation and Significant Accounting Policies - Additional Information (Details)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2018
USD ($)
Customer
Jun. 30, 2017
USD ($)
Customer
Jun. 30, 2018
USD ($)
Customer
Jun. 30, 2017
USD ($)
Customer
Dec. 31, 2017
USD ($)
Customer
Basis Of Presentation And Significant Accounting Policies [Line Items]          
Allocation of undistributed earnings to participating securities   $ 113,000 $ 0 $ 0  
Contractual obligation $ 0 $ 0 0 $ 0  
Cash equivalents 38,690,000   38,690,000   $ 43,471,000 [1]
Customer Concentration Risk [Member]          
Basis Of Presentation And Significant Accounting Policies [Line Items]          
Cash equivalents $ 0   $ 0    
Customer Concentration Risk [Member] | Trade Receivables [Member]          
Basis Of Presentation And Significant Accounting Policies [Line Items]          
Number of major partners | Customer     2   1
Customer Concentration Risk [Member] | Trade Receivables [Member] | Partner 1 [Member]          
Basis Of Presentation And Significant Accounting Policies [Line Items]          
Concentration risk, percentage (in hundredths)     84.00%   95.00%
Customer Concentration Risk [Member] | Trade Receivables [Member] | Partner 2 [Member]          
Basis Of Presentation And Significant Accounting Policies [Line Items]          
Concentration risk, percentage (in hundredths)     16.00%    
Customer Concentration Risk [Member] | Revenues [Member]          
Basis Of Presentation And Significant Accounting Policies [Line Items]          
Number of major partners | Customer 2 1 2 1  
Customer Concentration Risk [Member] | Revenues [Member] | Partner 1 [Member]          
Basis Of Presentation And Significant Accounting Policies [Line Items]          
Concentration risk, percentage (in hundredths) 80.00% 92.00% 66.00% 90.00%  
Customer Concentration Risk [Member] | Revenues [Member] | Partner 2 [Member]          
Basis Of Presentation And Significant Accounting Policies [Line Items]          
Concentration risk, percentage (in hundredths) 11.00%   22.00%    
[1] The condensed consolidated balance sheet as of December 31, 2017 has been derived from the audited consolidated financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.