Preferred Stock, Common Stock and Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares	Dec. 31, 2020	Dec. 31, 2019	Apr. 26, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock options issued and outstanding	4,077,259	3,114,371
Authorized for future option grants	1,402,433	1,587,155
Warrants to purchase common stock	1,841,879	2,713,561
Authorized for employee stock purchase plan	244,574	263,065
Total common stock reserved for future issuance	7,566,145	7,678,152	6,286,425