Income taxes - Narrative (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Capital loss carryforwards	$ 74,000
Loss carryforwards	31,841	$ 38,348
Deferred tax assets valuation allowance	41,929	43,467	$ 45,661	$ 125,894
Unrecognized tax benefits that, if recognized, would impact effective tax rate	6,800	6,000
Recognized income from the release of penalty reserves	700	0	$ 1,700
Accrued interest and penalties payable related to unrecognized tax benefits	700	$ 100
Estimated decrease in gross unrecognized tax positions within the next 12 months, maximum	500
State
Income Taxes [Line Items]
Tax credit carryforward	10,300
Loss carryforwards	6,800
Tax Year 2020
Income Taxes [Line Items]
Capital loss carryforwards subject to expiration	$ 73,000