Revenue Recognition Contract Assets and Liabilities (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
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										$ 1,124,413	$ 934,822
Contract with Customer, Asset, after Allowance for Credit Loss		$ 30,816				$ 28,888				30,816	28,888
Contract with Customer, Liability		613				408				613	408
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
Commission [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss		3,107				2,824				3,107	2,824
Mutual Fund Income [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss		5,989				6,746				5,989	6,746
Advisory Fees [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss		1,590				1,594				1,590	1,594
Bank Deposit Sweep Income [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss		687				3,454				687	3,454
Investment Banking Fees [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss		16,119				9,284				16,119	9,284
Other
Contracts with Customers Assets and Liabilities [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss		3,324				4,986				3,324	4,986
Investment Banking Fees [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Contract with Customer, Liability		$ 613				$ 408				613	408
Asset Management
Contracts with Customers Assets and Liabilities [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
Capital markets
Contracts with Customers Assets and Liabilities [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
Corporate/Other
Contracts with Customers Assets and Liabilities [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)
Private Client Division
Contracts with Customers Assets and Liabilities [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
Other [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										16,928	17,404
Other [Member] | Asset Management
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	5
Other [Member] | Capital markets
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										2,485	1,713
Other [Member] | Corporate/Other
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										127	2,398
Other [Member] | Private Client Division
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										14,316	13,288
Investment Banking, Capital Markets [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										139,763	72,779
Investment Banking, Capital Markets [Member] | Asset Management
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Investment Banking, Capital Markets [Member] | Capital markets
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										123,670	59,251
Investment Banking, Capital Markets [Member] | Corporate/Other
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Investment Banking, Capital Markets [Member] | Private Client Division
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										16,093	13,528
Advisory Fees [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										455,261	353,671
Advisory Fees [Member] | Asset Management
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										128,258	88,748
Advisory Fees [Member] | Capital markets
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										2	10
Advisory Fees [Member] | Corporate/Other
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										143	74
Advisory Fees [Member] | Private Client Division
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										326,858	264,839
Mutual Fund Income [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										35,180	40,045
Mutual Fund Income [Member] | Asset Management
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										3	0
Mutual Fund Income [Member] | Capital markets
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										9	3
Mutual Fund Income [Member] | Corporate/Other
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										67	17
Mutual Fund Income [Member] | Private Client Division
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										35,101	40,025
Investment Banking, Advisory [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										82,535	53,432
Investment Banking, Advisory [Member] | Asset Management
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										2,000	0
Investment Banking, Advisory [Member] | Capital markets
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										80,535	53,432
Investment Banking, Advisory [Member] | Corporate/Other
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Investment Banking, Advisory [Member] | Private Client Division
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Bank Deposit Sweep Income [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										34,829	117,422
Bank Deposit Sweep Income [Member] | Asset Management
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Bank Deposit Sweep Income [Member] | Capital markets
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Bank Deposit Sweep Income [Member] | Corporate/Other
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Bank Deposit Sweep Income [Member] | Private Client Division
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										34,829	117,422
Commissions From Sales And Trading [Member]
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										359,917	280,069
Commissions From Sales And Trading [Member] | Asset Management
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Commissions From Sales And Trading [Member] | Capital markets
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										185,542	131,380
Commissions From Sales And Trading [Member] | Corporate/Other
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										29	28
Commissions From Sales And Trading [Member] | Private Client Division
Contracts with Customers Assets and Liabilities [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										$ 174,346	$ 148,661

[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.