Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance Under Equity Incentive Plans (Detail)	Dec. 31, 2021 shares
Class Of Stock [Line Items]
Total reserved shares of common stock	20,971,553
2014 Equity Incentive Plan
Class Of Stock [Line Items]
Total reserved shares of common stock	16,086,987
2018 Inducement Plan
Class Of Stock [Line Items]
Total reserved shares of common stock	4,022,184
2014 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Total reserved shares of common stock	862,382