Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Outstanding at December 31, 2018	3,158,676
Granted	1,514,700
Exercised	(2,543)
Forfeited	(305,994)
Outstanding at December 31, 2019	4,364,839	3,158,676
Vested and expected to vest at December 31, 2019	4,281,589
Options exercisable at December 31, 2019	2,428,147
Weighted Average Exercise Price
Outstanding at December 31, 2018	$ 5.93
Granted	4.04
Exercised	1.09
Forfeited	5.59
Outstanding at December 31, 2019	5.30	$ 5.93
Vested and expected to vest at December 31, 2019	5.36
Options exercisable at December 31, 2019	$ 6.11
Weighted Average Remaining Contractual Term, Outstanding	7 years 3 months 25 days	7 years 6 months 10 days
Weighted Average Remaining Contractual Term, Vested and expected to vest at December 31, 2018	7 years 5 months 4 days
Weighted Average Remaining Contractual Term, Options exercisable at December 31, 2018	6 years 5 months 12 days
Aggregate Intrinsic Value, Outstanding	$ 132	$ 471
Aggregate Intrinsic Value, Vested and expected to vest at December 31, 2018	132
Aggregate Intrinsic Value, Options exercisable at December 31, 2018	$ 43

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.