Stock-Based Compensation - Summary of Compensation Expense Relating to Stock Options (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	$ 3,030	$ 2,812	$ 5,634	$ 5,491
Excess tax benefits from stock option activity or stock-based compensation expense recognized in cash flows from operations	0	0	0	0
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	1,805	1,670	3,395	3,279
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	1,225	1,142	2,239	2,212
Restricted Stock Units [Member] | Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	98	1,133	665	1,147
Restricted Stock Units [Member] | General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	206	551	1,027	581
Restricted Stock Units [Member] | Director [Member] | General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Compensation expense	$ 142	$ 122	$ 281	$ 245