Revenue from contracts with customers - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Total contract assets	$ 32,773	$ 37,192
Total deferred revenue	900	235
Capitalized contract costs	$ 1,400	$ 1,500
Commission From Equity Securities Transactions
Disaggregation of Revenue [Line Items]
Revenue settlement period (in days)	2 days
Commissions From Corporate Bond Transactions
Disaggregation of Revenue [Line Items]
Revenue settlement period (in days)	1 day
Mutual fund income
Disaggregation of Revenue [Line Items]
Revenue settlement period (in days)	90 days
Advisory fees
Disaggregation of Revenue [Line Items]
Revenue settlement period (in days)	90 days
Investment banking - capital markets
Disaggregation of Revenue [Line Items]
Revenue settlement period (in days)	90 days
Bank Deposit Sweep Income
Disaggregation of Revenue [Line Items]
Revenue settlement period (in days)	30 days