Convertible Preferred Stock and Stockholders' Equity - Additional Information (Details) - USD ($)		9 Months Ended
	Apr. 02, 2018	Sep. 30, 2018
Temporary Equity [Line Items]
Sale of common stock in initial public offering		$ 150,843,215
Convertible preferred shares converted to common stock	24,168,656
Initial Public Offering
Temporary Equity [Line Items]
Sale of common stock in initial public offering	$ 10,350,000
Offering price	$ 16.00
Net proceeds from initial public offering after underwriting discounts and commissions and offering expenses	$ 150,800,000
Convertible preferred shares converted to common stock	24,168,656