Stockholders' Equity - Summary of Stock Option Transactions (Detail) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options granted	219,310	452,650	3,387,810	452,650
2014 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance			2,837,739
Options granted			3,387,810
Ending balance	6,225,549		6,225,549		2,837,739
Options vested at end of period (shares)			2,284,607
Options vested and expected to vest at end of period (shares)	6,225,549		6,225,549
Weighted-Average Exercise Price per Share
Beginning balance (in dollars per share)			$ 4.18
Options granted (in dollars per share)			2.16
Ending balance (in dollars per share)	$ 3.08		3.08		$ 4.18
Options vested at end of period (in dollars per share)			4.61
Options vested and expected to vest at end of period (in dollars per share)	$ 3.08		$ 3.08
Weighted Average Remaining Contractual Term
Options outstanding at end of period			8 years 5 months 8 days		7 years 7 months 13 days
Options vested at end of period			6 years 11 months 12 days
Options vested and expected to vest at end of period			8 years 5 months 8 days
Aggregate Intrinsic Value
Options outstanding at end of period	$ 19		$ 19
Options vested and expected to vest at end of period	$ 19		$ 19