Income taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating Loss Carryforwards [Line Items]
Excise tax expense	$ 0	$ 0
Operating loss carryforwards	2,100,000	2,100,000
Net capital loss carryforwards	294,800,000	246,800,000
Income tax expense	200,000	0
Operating loss carryforward subject to expiration	7,800,000
Valuation allowance	30,239,000	6,765,000
Subsidiaries
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 128,400,000	$ 31,100,000