Revenues from contracts with customers - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	$ 34,252	$ 32,773
Deferred revenue (payables)	2,860	900
Commission
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	5,596	3,533
Mutual Fund Income
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	5,208	4,993
Advisory fees
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	4,309	5,368
Bank Deposit Sweep Income
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	6,434	9,057
Investment Banking Fees
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	6,710	5,136
Other
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	5,995	4,686
Investment Banking Fees
Capitalized Contract Cost [Line Items]
Deferred revenue (payables)	1,507	900
IRA fees
Capitalized Contract Cost [Line Items]
Deferred revenue (payables)	$ 1,353	$ 0