Convertible Preferred Stock and Stockholders' Equity - Summary of Stock Option Activity Under 2017 Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Convertible Preferred Stock And Stockholders Equity [Abstract]
Options Outstanding, Beginning Balance	1,635,427	822,557	822,557
Options Outstanding, Granted	608,185	681,950	1,009,125
Options Outstanding, Exercised	(140,073)		(69,615)
Options Outstanding, Forfeited	(20,321)		(126,640)
Options Outstanding, Ending Balance	2,083,218		1,635,427	822,557
Options Outstanding, Exercisable	544,379		521,327
Options Outstanding, Vested and expected to vest	2,083,218		1,635,427
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 1.64	$ 1.05	$ 1.05
Weighted Average Exercise Price, Granted	2.77		2.02
Weighted Average Exercise Price, Exercised	1.11	$ 2.02	1.04
Weighted Average Exercise Price, Forfeited	1.95		1.51
Weighted Average Exercise Price, Outstanding, Ending Balance	1.98		1.64	$ 1.05
Weighted Average Exercise Price, Exercisable	1.29		1.15
Weighted Average Exercise Price, Vested and expected to vest	$ 1.98		$ 1.64
Weighted Average Remaining Contractual Term (in years), Outstanding	8 years 9 months 21 days		8 years 9 months 21 days	8 years 5 months 4 days
Weighted Average Remaining Contractual Term (in years), Exercisable	7 years 7 months 13 days		7 years 10 months 28 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest	8 years 9 months 21 days		8 years 9 months 21 days
Aggregate Intrinsic Value, Outstanding	$ 1,641		$ 668	$ 678
Aggregate Intrinsic Value, Exercisable	806		452
Aggregate Intrinsic Value, Vested and expected to vest	$ 1,641		$ 668