Capital Structure - Summary of Common Stock Reserved for Future Issuance (Detail) - shares	Sep. 30, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common Stock reserved for future issuance	13,904,058	14,245,213
Two Thousand Fourteen Omnibus IncentivePlan [Member]
Class of Stock [Line Items]
Common Stock reserved for future issuance	26,774	41,079
Stock Options [Member]
Class of Stock [Line Items]
Common Stock reserved for future issuance	2,950,551	1,853,841
Warrants [Member]
Class of Stock [Line Items]
Common Stock reserved for future issuance	10,926,733	12,350,293