Revenue Recognition Disaggregation of Revenue (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										$ 1,124,413	$ 934,822
Interest										33,477	50,723	$ 52,484
Principal transactions, net										27,874	30,094	14,461
Revenues, Excluding Revenue From Contract With Customers, Other										12,903	17,740
Revenues, Excluding Revenue From Contract With Customers										74,254	98,557
Revenue		$ 422,908	$ 276,259	$ 264,730	$ 234,770	$ 295,881	$ 234,793	$ 250,935	$ 251,770	1,198,667	1,033,379	958,154
Commissions From Sales And Trading [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										359,917	280,069
Mutual Fund Income [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										35,180	40,045
Advisory Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										455,261	353,671
Investment Banking, Capital Markets [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										139,763	72,779
Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										82,535	53,432
Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										34,829	117,422
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										16,928	17,404
Private Client Division
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										601,543	597,763
Interest										25,148	35,809
Principal transactions, net										3,300	3,341
Revenues, Excluding Revenue From Contract With Customers, Other										12,092	16,496
Revenues, Excluding Revenue From Contract With Customers										40,540	55,646
Revenue	[1]									642,083	653,409	617,871
Private Client Division | Commissions From Sales And Trading [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										174,346	148,661
Private Client Division | Mutual Fund Income [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										35,101	40,025
Private Client Division | Advisory Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										326,858	264,839
Private Client Division | Investment Banking, Capital Markets [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										16,093	13,528
Private Client Division | Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Private Client Division | Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										34,829	117,422
Private Client Division | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										14,316	13,288
Asset Management
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										130,261	88,753
Interest										0	0
Principal transactions, net										0	0
Revenues, Excluding Revenue From Contract With Customers, Other										13	2
Revenues, Excluding Revenue From Contract With Customers										13	2
Revenue	[1]									130,274	88,755	71,696
Asset Management | Commissions From Sales And Trading [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Asset Management | Mutual Fund Income [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										3	0
Asset Management | Advisory Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										128,258	88,748
Asset Management | Investment Banking, Capital Markets [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Asset Management | Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										2,000	0
Asset Management | Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Asset Management | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	5
Capital markets
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										392,243	245,789
Interest										7,749	13,302
Principal transactions, net										26,306	31,621
Revenues, Excluding Revenue From Contract With Customers, Other										454	118
Revenues, Excluding Revenue From Contract With Customers										34,509	45,041
Revenue										426,752	290,830	272,719
Capital markets | Commissions From Sales And Trading [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										185,542	131,380
Capital markets | Mutual Fund Income [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										9	3
Capital markets | Advisory Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										2	10
Capital markets | Investment Banking, Capital Markets [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										123,670	59,251
Capital markets | Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										80,535	53,432
Capital markets | Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Capital markets | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										2,485	1,713
Corporate/Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										366	2,517
Interest										580	1,612
Principal transactions, net										(1,732)	4,868
Revenues, Excluding Revenue From Contract With Customers, Other										344	1,124
Revenues, Excluding Revenue From Contract With Customers										(808)	(2,132)
Revenue										(442)	385	$ (4,132)
Corporate/Other | Commissions From Sales And Trading [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										29	28
Corporate/Other | Mutual Fund Income [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										67	17
Corporate/Other | Advisory Fees [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										143	74
Corporate/Other | Investment Banking, Capital Markets [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Corporate/Other | Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Corporate/Other | Investment Banking, Advisory [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Corporate/Other | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										$ 127	$ 2,398

[1] (1) Clients investing in the OAM advisory program are charged fees based on the value of AUM. Advisory fees were allocated 10.0% to the Asset Management and 90.0% to the Private Client segments.