Derivative liabilities and redeemable convertible preferred stock liability - Additional Information (Detail) - USD ($)			3 Months Ended
	Oct. 19, 2020	Dec. 23, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Aug. 16, 2018	Jun. 06, 2018	Apr. 20, 2018
Derivative Liabilities And Convertible Preferred Stock Liability [Line Items]
Class of warrant or right, number of securities called by warrants or rights			134,112
Percentage of principal amount of notes covered by warrants			25.00%
Warrants issued expiry period			10 years
Warrants issued closing date			Apr. 20, 2018
Changes in fair value of the warrants				$ 137,000
Derivative Financial Instruments, Liabilities [Member]
Derivative Liabilities And Convertible Preferred Stock Liability [Line Items]
Changes in fair value of the warrants			$ 0	$ 20,000
Derivative Financial Instruments, Liabilities [Member] | Warrant [Member]
Derivative Liabilities And Convertible Preferred Stock Liability [Line Items]
Fair value of warrants upon issuance							$ 238,000	$ 700,000
Fair value of the warrants			$ 0		$ 0
Mandatorily Redeemable Preferred Stock [Member]
Derivative Liabilities And Convertible Preferred Stock Liability [Line Items]
Redeemable convertible preferred stock liability at a fair value		$ 3,200,000
Series A
Derivative Liabilities And Convertible Preferred Stock Liability [Line Items]
Warrants exercise price per share			$ 9.32
Sale of stock issue price per share						$ 9.32
Series A | Derivative Financial Instruments, Liabilities [Member]
Derivative Liabilities And Convertible Preferred Stock Liability [Line Items]
Warrants exercised			0	0
Series B Two Preferred Stock [Member]
Derivative Liabilities And Convertible Preferred Stock Liability [Line Items]
Sale of Stock, Number of Shares Issued in Transaction	3,569,630	3,569,630
Sale of stock issue price per share		$ 11.20563
Change in fair value of liability			$ 0	$ 166,000
Maximum [Member]
Derivative Liabilities And Convertible Preferred Stock Liability [Line Items]
Warrants issued closing date			Jun. 06, 2018