Income taxes - Deferred tax assets (liabilities) and unrecognized tax benefits (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Income taxes
Unrecognized tax benefits	$ 0	$ 0
Amounts in uncertain tax position	0
Accrued interest	0	0
Deferred tax assets:
Net operating loss carryforwards	13,724	47,282
Tax credit carryforwards	28,427	32,060
Lease liability	5,544	6,318
Deferred revenue	1,675	17,984
Stock compensation	5,157	4,630
Non-deductible accruals and reserves	2,613	1,603
Capitalized research expenses	31,347	14,351
Intangibles	554	610
Other temporary differences		(1)
Total deferred tax assets	89,041	124,837
Less valuation allowance	(82,612)	(117,416)
Net deferred tax assets	6,429	7,421
Deferred tax liabilities
Right of use assets	(3,691)	(4,231)
Depreciation and amortization	$ (2,738)	$ (3,190)