Revenue from contracts with customers - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Contracts with Customers Assets and Liabilities [Line Items]
Total receivables	$ 39,861	$ 32,773
Total deferred revenue	1,118	900
Investment banking fees
Contracts with Customers Assets and Liabilities [Line Items]
Total deferred revenue	1,118	900
Commission
Contracts with Customers Assets and Liabilities [Line Items]
Total receivables	4,554	3,533
Mutual fund income
Contracts with Customers Assets and Liabilities [Line Items]
Total receivables	5,365	4,993
Advisory fees
Contracts with Customers Assets and Liabilities [Line Items]
Total receivables	5,746	5,368
Bank deposit sweep income
Contracts with Customers Assets and Liabilities [Line Items]
Total receivables	5,223	9,057
Investment banking fees
Contracts with Customers Assets and Liabilities [Line Items]
Total receivables	12,847	5,136
Other
Contracts with Customers Assets and Liabilities [Line Items]
Total receivables	$ 6,126	$ 4,686