Summary of significant accounting policies - Deferred Contract Costs (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Accounting Policies [Abstract]
Total amortization of contract costs	$ 5,600,000	$ 4,200,000	$ 15,600,000	$ 12,100,000
Impairment losses	$ 0	$ 0	$ 0	$ 0