Revenues from contracts with customers - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	$ 32,927	$ 37,192
Deferred revenue (payables)	994	235
Commission
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	5,990	2,886
Mutual Fund Income
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	5,078	6,205
Advisory fees
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	3,404	4,546
Bank Deposit Sweep Income
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	6,625	595
Investment Banking Fees
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	7,065	17,765
Other
Capitalized Contract Cost [Line Items]
Contract assets (receivables)	4,765	5,195
Investment Banking Fees
Capitalized Contract Cost [Line Items]
Deferred revenue (payables)	230	235
IRA fees
Capitalized Contract Cost [Line Items]
Deferred revenue (payables)	$ 764	$ 0