Fair value measurements - Changes in contingent consideration (Details) - Contingent Consideration Derivative - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance of Level 3 at beginning of year	$ 0	$ 0	$ 0
Sixth Street Contingent Consideration valuation as of Sixth Street Closing Date	33,832	0	0
Change in net present value of Sixth Street Contingent Consideration	2,029	0	0
Balance of Level 3 at end of year	$ 35,861	$ 0	$ 0