Quarterly report pursuant to Section 13 or 15(d)

Related Party Transactions - Additional Information (Details)

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Related Party Transactions - Additional Information (Details)
9 Months Ended
Sep. 30, 2018
USD ($)
shares
Private Placement | Longitude Venture Partners III, L.P.  
Related Party Transaction [Line Items]  
Ownership percentage of merger company 15.30%
Investments $ 20,000,000
Private Placement | CDK Associates, L.L.C.  
Related Party Transaction [Line Items]  
Ownership percentage of merger company 4.99%
Investments $ 7,000,000
Private Placement | Excel Venture Fund II, L.P.  
Related Party Transaction [Line Items]  
Investments $ 333,000
Private Placement | Excel Venture Fund II, L.P. | Minimum  
Related Party Transaction [Line Items]  
Ownership percentage of merger company 5.00%
Public Offering | Longitude Venture Partners III, L.P. | Common Stock  
Related Party Transaction [Line Items]  
Stock ssued | shares 365,000
Public Offering | CDK Associates, L.L.C. | Common Stock  
Related Party Transaction [Line Items]  
Stock ssued | shares 545,454
Public Offering | BVF Partners L.P.  
Related Party Transaction [Line Items]  
Ownership percentage of merger company 7.60%
Investments $ 15,300,000