Registered Offering and Warrants - Schedule of Pre-funded Warrants and Warrants Outstanding (Detail)	3 Months Ended
	Mar. 31, 2021 $ / shares shares
Class Of Warrant Or Right [Line Items]
Beginning Balance	19,000,000
Warrant exercised	12,791,000
Ending Balance	6,209,000
Warrants [Member]
Class Of Warrant Or Right [Line Items]
Warrant description	Warrants
Warrant classification	Liability
Warrant exercise price | $ / shares	$ 5.95
Warrant expiration date	Mar. 17, 2025
Beginning Balance	19,000,000
Warrant exercised	12,791,000
Ending Balance	6,209,000