Stockholders' Equity - Additional Information (Details) - USD ($)						1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	May 21, 2020	Sep. 06, 2018	May 21, 2018	Jan. 04, 2018	Dec. 03, 2015	Jan. 31, 2018	Nov. 30, 2017	Jun. 30, 2020	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Stockholders Equity [Line Items]
Common stock, voting right										one
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs, shares	9,433,963
Offering price, per share	$ 13.25
Proceeds from issuance of common stock	$ 117,100,000									$ 117,094,000	$ 291,311,000
Common stock, par value								$ 0.0001		$ 0.0001		$ 0.0001
Issuance of common stock in connection with a public offering net of underwriting discounts, commissions and offering costs								$ 117,094,000	$ 291,344,000
Shares of common stock, repurchase										3,839,251		4,648,526
Series A Convertible Preferred Stock | Stock Restriction Agreements
Stockholders Equity [Line Items]
Shares subject to forfeiture							1,305,427
Founder
Stockholders Equity [Line Items]
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs, shares		1,795,023	251,547
Percentage of fully diluted share capital				15.00%
Increased in equity capital amount				$ 300,000,000
Common stock issued price per share		$ 9.63	$ 2.61
Additional shares of restricted stock subject to vesting restrictions		1,795,023	251,547
Common Stock
Stockholders Equity [Line Items]
Conversion of convertible preferred stock into common stock, shares									30,493,460
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs, shares								9,433,963	19,837,500
Issuance of common stock in connection with a public offering net of underwriting discounts, commissions and offering costs								$ 1,000	$ 2,000
Common Stock | Stock Restriction Agreements
Stockholders Equity [Line Items]
Unrestricted shares of common stock were subject to service vesting conditions						4,580,444
Founder Shares
Stockholders Equity [Line Items]
Issuance of common stock in connection with a public offering, net of underwriting discounts, commissions, and offering costs, shares					9,160,888
Common stock, par value					$ 0.0001
Issuance of common stock in connection with a public offering net of underwriting discounts, commissions and offering costs					$ 4,100
Common Stock vesting percentage				50.00%
Common stock vesting period				5 years