Common and Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended				12 Months Ended
	Jun. 03, 2019	May 07, 2018	Apr. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 28, 2018	Dec. 31, 2016
Class Of Stock [Line Items]
Convertible preferred stock, shares authorized							10,000,000	10,000,000
Number of stock, par value per share							$ 0.0001	$ 0.0001
Number of stock, shares issued							0	0
Number of stock, shares outstanding							0	0
Common stock, shares authorized				140,000,000			300,000,000	300,000,000		122,000,000
Common stock, par value per share							$ 0.0001	$ 0.0001
Common stock, shares issued							47,227,065	42,414,294
Common stock, shares outstanding							47,227,065	42,414,294
Preferred stock, shares authorized				103,283,818						91,739,149
Net proceeds from sale of convertible preferred stock								$ 59,881	$ 42,867
Net proceeds from issuance initial public offering after Deducting Underwriting Discounts Commissions and offering related transaction costs								$ 79,055
Common stock, par value							$ 0.0001	$ 0.0001
Shares issued offering value							$ 2,995	$ 75,852	$ 44
Proceeds from sale of common stock							$ 26,085
Maximum
Class Of Stock [Line Items]
Shares issued offering value	$ 250,000
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Number of stock, shares issued					2,879,288	659,821
Shares price per share					$ 12.125	$ 12.125
Gross proceeds from issuance of convertible preferred stock					$ 34,900	$ 8,000
Issuance price per share									$ 12.125
Series C Convertible Preferred Stock
Class Of Stock [Line Items]
Number of stock, shares issued			322,852	3,590,573
Shares price per share			$ 15.3317	$ 15.3317
Preferred stock, shares designated				11,544,669
Net proceeds from sale of convertible preferred stock			$ 5,000	$ 54,900
Issuance price per share								$ 15.3317
Common Stock
Class Of Stock [Line Items]
Common shares issued upon conversion of preferred shares								32,073,149
Common stock, shares outstanding							47,227,065	42,414,294	4,830,389		4,303,538
Issuance of common stock							253,334	5,000,000	12,711
Shares issued offering value								$ 1
IPO
Class Of Stock [Line Items]
Common stock, shares authorized		300,000,000
Common stock, par value per share		$ 0.0001
Preferred stock, shares authorized		10,000,000
Issuance of common stock		5,000,000
Issuance price per share		$ 17.00
Net proceeds from issuance initial public offering after Deducting Underwriting Discounts Commissions and offering related transaction costs		$ 75,900
Approximate underwriting discounts commissions and offering related transaction costs		$ 9,100
Common stock, par value		$ 0.0001
Preferred stock, par value		$ 0.0001
IPO | Common Stock
Class Of Stock [Line Items]
Common shares issued upon conversion of preferred shares		32,073,149					32,100,000
ATM Equity offering program
Class Of Stock [Line Items]
Shares issued offering value							$ 26,086
ATM Equity offering program | Sales Agreement | Cowen
Class Of Stock [Line Items]
Issuance of common stock							3,974,908
Proceeds from sale of common stock							$ 26,100
Payments for commissions and other offering expenses							$ 1,400
ATM Equity offering program | Sales Agreement | Cowen | Maximum
Class Of Stock [Line Items]
Proceeds from sale of common stock	$ 75,000
Percentage of gross sales proceeds of common stock payable as compensation	3.00%
Reimbursement of expenses	$ 100
ATM Equity offering program | Common Stock
Class Of Stock [Line Items]
Issuance of common stock							3,974,908
Shares issued offering value							$ 1
ATM Equity offering program | Common Stock | Maximum
Class Of Stock [Line Items]
Shares issued offering value	$ 75,000