Revenue from contracts with customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 1,229,048	$ 1,072,500
Interest	135,537	104,550	$ 60,713
Principal transactions, net	54,684	65,347	21,031
Other	13,227	6,428
Total other sources of revenue	203,448	176,325
Total revenue	1,432,496	1,248,825	1,110,941
Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	5,064	434
Interest	7,524	4,249
Principal transactions, net	39	6,375
Other	238	1,683
Total other sources of revenue	7,801	12,307
Total revenue	12,865	12,741	(1,802)
Commissions from sales and trading
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	376,910	317,768
Commissions from sales and trading | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	14	23
Mutual fund and insurance income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	32,800	31,480
Mutual fund and insurance income | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	21	16
Advisory fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	483,433	415,679
Advisory fees | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	42	229
Investment banking - capital markets
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	69,177	48,042
Investment banking - capital markets | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
Investment banking - advisory
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	107,270	69,623
Investment banking - advisory | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
Bank deposit sweep income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	138,770	172,807
Bank deposit sweep income | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	20,688	17,101
Other | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	4,987	166
Asset Management Segment | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	867,757	797,795
Interest	88,714	85,105
Principal transactions, net	3,263	3,400
Other	12,318	3,887
Total other sources of revenue	104,295	92,392
Total revenue	972,052	890,187
Asset Management Segment | Commissions from sales and trading | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	188,783	155,039
Asset Management Segment | Mutual fund and insurance income | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	32,775	31,457
Asset Management Segment | Advisory fees | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	483,391	415,450
Asset Management Segment | Investment banking - capital markets | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	11,155	7,543
Asset Management Segment | Investment banking - advisory | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	46	0
Asset Management Segment | Bank deposit sweep income | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	138,770	172,807
Asset Management Segment | Other | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	12,837	15,499
Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	356,227	274,271
Interest	39,299	15,196
Principal transactions, net	51,382	55,572
Other	671	858
Total other sources of revenue	91,352	71,626
Total revenue	447,579	345,897	$ 337,821
Capital Markets | Commissions from sales and trading | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	188,113	162,706
Capital Markets | Mutual fund and insurance income | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	4	7
Capital Markets | Advisory fees | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
Capital Markets | Investment banking - capital markets | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	58,022	40,499
Capital Markets | Investment banking - advisory | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	107,224	69,623
Capital Markets | Bank deposit sweep income | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0
Capital Markets | Other | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 2,864	$ 1,436