Stock-Based Compensation - Summary of Company's Stock Option Activity and Related Information (Detail) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Shares Available for Grant
Shares Available for Grant, Beginning balance	948,415
Shares Available for Grant, Additional options authorized	9,137,667
Shares Available for Grant, Options granted	(736,579)
Shares Available for Grant, Options cancelled	2,165,317
Shares Available for Grant, Withheld shares to pay for taxes on released RSUs	45,913
Shares Available for Grant, RSUs granted	(5,962,979)
Shares Available for Grant, Ending balance	6,155,182	948,415
Shares Available for Grant, RSUs forfeited	557,428
Number of Stock Options Outstanding
Number of Stock Options Outstanding, Beginning balance	11,165,846
Number of Stock Options Outstanding, Options granted	736,579
Number of Stock Options Outstanding, Options exercised	(20,579)
Number of Stock Options Outstanding, Options cancelled	(2,165,317)
Number of Stock Options Outstanding, Ending balance	9,716,529	11,165,846
Number of Stock Options Outstanding, Vested and exercisable	4,870,115
Number of Stock Options Outstanding, Vested and expected to vest	9,297,531
Weighted- Average Exercise Price
Weighted- Average Exercise Price, Beginning balance | $ / shares	$ 7.44
Weighted- Average Exercise Price, Options granted | $ / shares	1.97
Weighted- Average Exercise Price, Options exercised | $ / shares	0.72
Weighted- Average Exercise Price, Options cancelled | $ / shares	6.27
Weighted- Average Exercise Price, Ending balance | $ / shares	7.26	$ 7.44
Weighted- Average Exercise Price, Vested and exercisable | $ / shares	7.04
Weighted- Average Exercise Price, Vested and expected to vest | $ / shares	$ 7.28
Weighted- Average Remaining Contractual Life (Years)
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	7 years 10 months 24 days	7 years 7 months 6 days
Weighted- Average Remaining Contractual Life (Years), Vested and exercisable	7 years 3 months 18 days
Weighted- Average Remaining Contractual Life (Years), Vested and expected to vest	7 years 9 months 18 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value | $	$ 907	$ 1,907
Aggregate Intrinsic Value, Vested and exercisable | $	626
Aggregate Intrinsic Value, Vested and expected to vest | $	$ 871