Revenue from contracts with customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	$ 275,191	$ 272,514	$ 812,084	$ 771,335
Interest	26,430	17,361	78,691	38,667
Principal transactions, net	16,892	6,502	46,635	10,124
Other	(5,846)	(2,266)	3,126	(22,765)
Total other sources of revenue	37,476	21,597	128,452	26,026
Total revenue	312,667	294,111	940,536	797,361
Corporate/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	42	61	198	306
Interest	936	625	3,077	730
Principal transactions, net	2,484	(1,251)	6,292	(1,543)
Other	545	245	1,622	362
Total other sources of revenue	3,965	(381)	10,991	(451)
Total revenue	4,007	(320)	11,189	(145)
Private Client | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	174,814	167,793	525,942	469,541
Interest	21,248	14,471	64,230	32,987
Principal transactions, net	(612)	(884)	1,509	(5,050)
Other	(2,196)	(2,766)	6,239	(23,546)
Total other sources of revenue	18,440	10,821	71,978	4,391
Total revenue	193,254	178,614	597,920	473,932
Asset Management | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	25,188	24,865	72,023	76,289
Interest	0	0	0	0
Principal transactions, net	0	0	0	0
Other	(4,358)	5	(5,036)	13
Total other sources of revenue	(4,358)	5	(5,036)	13
Total revenue	20,830	24,870	66,987	76,302
Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	75,147	79,795	213,921	225,199
Interest	4,246	2,265	11,384	4,950
Principal transactions, net	15,020	8,637	38,834	16,717
Other	163	250	301	406
Total other sources of revenue	19,429	11,152	50,519	22,073
Total revenue	94,576	90,947	264,440	247,272
Commissions from sales and trading
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	75,719	82,001	235,524	258,542
Commissions from sales and trading | Corporate/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	4	12	18	29
Commissions from sales and trading | Private Client | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	36,176	39,290	112,766	120,753
Commissions from sales and trading | Asset Management | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Commissions from sales and trading | Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	39,539	42,699	122,740	137,760
Mutual fund and insurance income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	8,214	7,607	23,650	23,765
Mutual fund and insurance income | Corporate/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	4	3	12	25
Mutual fund and insurance income | Private Client | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	8,209	7,603	23,632	23,733
Mutual fund and insurance income | Asset Management | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Mutual fund and insurance income | Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	1	1	6	7
Advisory fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	107,969	102,927	310,214	326,098
Advisory fees | Corporate/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	7	7	23	25
Advisory fees | Private Client | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	82,774	78,055	238,168	249,667
Advisory fees | Asset Management | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	25,188	24,865	72,023	76,289
Advisory fees | Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	117
Investment banking - capital markets
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	19,410	9,123	38,471	34,022
Investment banking - capital markets | Corporate/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Investment banking - capital markets | Private Client | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	2,115	1,950	5,590	7,615
Investment banking - capital markets | Asset Management | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Investment banking - capital markets | Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	17,295	7,173	32,881	26,407
Investment banking - advisory
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	18,001	29,270	56,883	59,494
Investment banking - advisory | Corporate/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Investment banking - advisory | Private Client | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	35
Investment banking - advisory | Asset Management | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Investment banking - advisory | Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	18,001	29,270	56,883	59,459
Bank deposit sweep income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	42,304	35,769	135,273	54,968
Bank deposit sweep income | Corporate/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Bank deposit sweep income | Private Client | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	42,304	35,769	135,273	54,968
Bank deposit sweep income | Asset Management | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Bank deposit sweep income | Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	3,574	5,817	12,069	14,446
Other | Corporate/Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	27	39	145	227
Other | Private Client | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	3,236	5,126	10,513	12,770
Other | Asset Management | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	0	0	0	0
Other | Capital Markets | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers:	$ 311	$ 652	$ 1,411	$ 1,449