Income taxes - Schedule of Activity Related to Unrecognized Tax Benefits, Excluding Federal Tax Benefit of State Tax Deductions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Change in unrecognized tax benefits
Balance at beginning of year	$ 7,725	$ 8,196	$ 7,435
Additions for tax positions of prior years	151	0	1,363
Reductions for tax positions of prior years	(680)	0	0
Settlements	0	(9)	0
Reductions due to lapse of statutes of limitations	(551)	(462)	(602)
Balance as of end of year	$ 6,645	$ 7,725	$ 8,196