Revenue from contracts with customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 1,424,063	$ 1,229,048
Interest	152,982	135,537	$ 104,550
Principal transactions, net	50,214	54,684	65,347
Other	10,812	13,227
Total other sources of revenue	214,008	203,448
Total revenue	1,638,071	1,432,496	1,248,825
Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	5,041	5,064
Interest	6,497	7,524
Principal transactions, net	(242)	39
Other	57	238
Total other sources of revenue	6,312	7,801
Total revenue	11,353	12,865	12,741
Commissions from sales and trading
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	431,402	376,910
Commissions from sales and trading | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	38	14
Mutual fund and insurance income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	33,013	32,800
Mutual fund and insurance income | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	25	21
Advisory fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	555,439	483,433
Advisory fees | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	52	42
Investment banking - capital markets
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	152,872	69,177
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	113,520	107,270
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	114,811	138,770
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	23,006	20,688
Other | Corporate/Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	4,926	4,987
Asset Management Segment | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	934,387	867,757
Interest	87,982	88,714
Principal transactions, net	3,125	3,263
Other	9,909	12,318
Total other sources of revenue	101,016	104,295
Total revenue	1,035,403	972,052
Asset Management Segment | Commissions from sales and trading | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	202,336	188,783
Asset Management Segment | Mutual fund and insurance income | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	32,984	32,775
Asset Management Segment | Advisory fees | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	555,387	483,391
Asset Management Segment | Investment banking - capital markets | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	12,107	11,155
Asset Management Segment | Investment banking - advisory | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	454	46
Asset Management Segment | Bank deposit sweep income | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	114,811	138,770
Asset Management Segment | Other | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	16,308	12,837
Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	484,635	356,227
Interest	58,503	39,299
Principal transactions, net	47,331	51,382
Other	846	671
Total other sources of revenue	106,680	91,352
Total revenue	591,315	447,579	$ 345,897
Capital Markets | Commissions from sales and trading | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	229,028	188,113
Capital Markets | Mutual fund and insurance income | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	4	4
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	140,765	58,022
Capital Markets | Investment banking - advisory | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	113,066	107,224
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	$ 1,772	$ 2,864