Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance (Parenthetical) (Details)

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Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance (Parenthetical) (Details) - shares
Jan. 01, 2019
Sep. 30, 2019
Dec. 31, 2018
Class Of Stock [Line Items]      
Treasury stock, shares at cost   420,000 357,000
2016 Equity Incentive Plan      
Class Of Stock [Line Items]      
Number of authorized shares increased 384,045    
2016 Employee Stock Purchase Plan      
Class Of Stock [Line Items]      
Number of authorized shares increased 96,000