Income taxes - Reconciliation of Income Tax Provision (Benefit) (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Federal income tax expense at statutory rate	21.00%	21.00%
State income tax, net of federal benefit	7.30%	5.20%
Permanent differences	0.60%	(0.10%)
Stock-based compensation	(3.60%)	(9.30%)
Research and development credit	5.80%	8.30%
Leases	5.40%	34.40%
Right-of-use assets	0.00%	(26.10%)
Fixed assets	(2.70%)	(7.20%)
Foreign differential	0.00%	0.30%
Other	0.90%	(0.60%)
Change in valuation allowance	(34.60%)	(26.00%)
Effective income tax rate (expense) benefit	0.10%	(0.10%)