Convertible Preferred Stock and Stockholder's Equity (Deficit) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 06, 2019	Mar. 05, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Temporary Equity And Stockholders Equity [Line Items]
Preferred stock, shares authorized			5,000,000
Preferred stock, shares issued			0
Preferred stock, shares outstanding			0
Related Party Common Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Warrants exercised price			$ 2.196
Initial Public Offering | Common Stock Warrants Related to Convertible Preferred Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Common stock warrants issued	54,903
Adjustments to additional paid in capital	$ 0.8
Warrants exercised price			$ 3.096
Initial Public Offering | Related Party Common Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Common stock warrants exercised	91,446
Warrants exercised price	$ 17.00
Common stock issued upon exercise of common stock warrants	79,632
Convertible Preferred Stock
Temporary Equity And Stockholders Equity [Line Items]
Convertible preferred stock, shares outstanding		18,670,259		18,670,328	17,562,214	17,510,045
Fractional shares that will be settled in cash			69
Common Stock
Temporary Equity And Stockholders Equity [Line Items]
Conversion of stock, common stock issued		18,670,259
Fractional shares that will be settled in cash			45