Income taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Effective income tax rate, percent	(1.50%)	(4.23%)	(2.00%)
Valuation allowance	$ 97,010	$ 69,766
Valuation allowance increase	27,200
Research and development tax credits	13,301	0
Net operating loss carryforward, amount limited by Section 382	3,300
Unrecognized tax benefits	3,608	10,580	$ 146	$ 146
Potential tax associated with foreign earnings being repatriated	200
Deferred tax liability, CARES Act		$ 2,600
Payment of deferred taxes, CARES Act	1,500
Domestic Tax Authority
Income Taxes [Line Items]
Net operating loss carryforward	189,200
Net operating loss carryforward subject to expiration	101,900
Net operating loss carryforward not subject to expiration	87,300
Research and development tax credits	9,700
Domestic Tax Authority | Tax Year 2010-2012
Income Taxes [Line Items]
Net operating loss carryforward subject to expiration	3,600
Domestic Tax Authority | CorpU
Income Taxes [Line Items]
Net operating loss carryforward subject to expiration	3,300
State and Local Jurisdiction
Income Taxes [Line Items]
Net operating loss carryforward	34,000
Research and development tax credits	$ 8,600