Summary of significant accounting policies - Deferred contract costs, R&D, Advertising, Interest (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Concentration Risk [Line Items]
Benefit period	5 years
Total amortization of contract costs	$ 12,500,000	$ 8,000,000	$ 5,200,000
Impairment losses	0	0	0
Trade accounts receivable, net	79,143,000	69,056,000
Advertising costs	17,000,000	13,400,000	8,700,000
Interest expense from debt financing	2,500,000	10,800,000	21,900,000
Interest income from cash investments		100,000	500,000
Accounts Receivable | Credit Concentration Risk
Concentration Risk [Line Items]
Trade accounts receivable, net	$ 17,400,000	$ 19,800,000	$ 6,000,000
Accounts Receivable | Customer Concentration Risk | One Distributor
Concentration Risk [Line Items]
Concentration risk percentage	22.00%	23.00%