Income taxes - Deferred tax assets (liabilities) and unrecognized tax benefits (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Income taxes
Unrecognized tax benefits	$ 0	$ 0
Amounts in uncertain tax position	0	0
Accrued interest	0	0
Deferred tax assets:
Net operating loss carryforwards	47,282	56,756
Tax credit carryforwards	32,060	30,122
Lease liability	6,318	12,012
Deferred revenue	17,984	11,485
Stock compensation	4,630	7,784
Non-deductible accruals and reserves	1,603	1,507
Capitalized research expenses	14,351
Intangibles	610	664
Other temporary differences	(1)
Total deferred tax assets	124,837	120,330
Less valuation allowance	(117,416)	(107,563)
Net deferred tax assets	7,421	12,767
Deferred tax liabilities
Right of use assets	(4,231)	(9,128)
Depreciation and amortization	$ (3,190)	(3,632)
Other temporary differences		$ (7)