Fair Value Of Financial Instruments (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Thousands		Dec. 31, 2022		Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		$ 731,752		$ 1,157,004
Available-for-sale securities		1,636,041	[1]	2,113,893
Investments		99,376		117,804
Cash equivalents measured at NAV		1,650		3,004
Derivative Assets		142,042	[2]	52,129	[3]
Total Assets		2,610,861		3,443,834
Financial instruments sold, but not yet purchased, at fair value		454,817		756,150
Derivative contracts, Liabilities		142,028	[4]	52,147	[5]
Total Liabilities		596,845		808,297
U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		38,956		10,774
Financial instruments sold, but not yet purchased, at fair value		254,265		377,023
U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		73,608		143,793
Available-for-sale securities		2,148	[1]	1,808
Financial instruments sold, but not yet purchased, at fair value		3,971		37,395
Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		8,270		132,087
Available-for-sale securities		207,725	[1]	291,054
Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		202,169		255,999
Available-for-sale securities		566,294	[1]	791,893
Financial instruments sold, but not yet purchased, at fair value		134,381		153,852
Corporate Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		38,129		75,056
Investments		23,597		21,308
Financial instruments sold, but not yet purchased, at fair value		11,590		28,482
State And Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		126,237		162,335
Available-for-sale securities		2,351	[1]	2,399
Auction Rate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		14,681		13,032
Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		37,136		60,406
Investments In Funds And Partnerships Measured At Net Asset Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		23,962		23,058
Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned				335,050
Financial instruments sold, but not yet purchased, at fair value				156,628
Mortgage-Backed Securities [Member] | Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		172,642
Available-for-sale securities		791,022	[1]	952,186
Financial instruments sold, but not yet purchased, at fair value		44,793
Mortgage-Backed Securities [Member] | Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		66,113	[1]	73,985
Mortgage-Backed Securities [Member] | Non-Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		388	[1]	568
Sovereign Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		731,752
Financial instruments sold, but not yet purchased, at fair value				2,770
Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		71,741	[6]	41,910	[7]
Financial instruments sold, but not yet purchased, at fair value	[8]	5,817
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned				84,450
Available-for-sale securities		0
Investments		10,045		24,110
Derivative Assets	[2]	0
Total Assets		87,073		108,560
Financial instruments sold, but not yet purchased, at fair value		265,943		405,505
Derivative contracts, Liabilities	[4]	0
Total Liabilities		265,943		405,505
Level 1 [Member] | U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		38,956		10,774
Financial instruments sold, but not yet purchased, at fair value		254,265		377,023
Level 1 [Member] | U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value		0
Level 1 [Member] | Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		689		183
Financial instruments sold, but not yet purchased, at fair value		88
Level 1 [Member] | Corporate Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		37,383		73,493
Investments		9,928		13,893
Financial instruments sold, but not yet purchased, at fair value		11,590		28,482
Level 1 [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		117		10,217
Level 1 [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value		0
Level 1 [Member] | Sovereign Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		77,028
Level 1 [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments sold, but not yet purchased, at fair value	[8]	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned				980,766
Available-for-sale securities		1,636,041		2,113,893
Investments		1,836		16,013
Derivative Assets		142,042	[2]	52,129	[3]
Total Assets		2,362,576		3,162,801
Financial instruments sold, but not yet purchased, at fair value		183,093		350,645
Derivative contracts, Liabilities		142,028	[4]	52,147	[5]
Total Liabilities		325,121		402,792
Level 2 [Member] | U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		73,608		143,793
Available-for-sale securities		2,148		1,808
Financial instruments sold, but not yet purchased, at fair value		3,971		37,395
Level 2 [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		6,091		67,381
Available-for-sale securities		207,725		291,054
Level 2 [Member] | Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		201,480		255,816
Available-for-sale securities		566,294		791,893
Financial instruments sold, but not yet purchased, at fair value		134,293		153,852
Level 2 [Member] | Corporate Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		746		1,338
Investments		1,791		1,661
Level 2 [Member] | State And Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		126,237		162,335
Available-for-sale securities		2,351		2,399
Level 2 [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		45		14,352
Level 2 [Member] | Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned				335,050
Financial instruments sold, but not yet purchased, at fair value				156,628
Level 2 [Member] | Mortgage-Backed Securities [Member] | Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		172,642
Available-for-sale securities		791,022		952,186
Financial instruments sold, but not yet purchased, at fair value		44,793
Level 2 [Member] | Mortgage-Backed Securities [Member] | Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		66,113		73,985
Level 2 [Member] | Mortgage-Backed Securities [Member] | Non-Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		388		568
Level 2 [Member] | Sovereign Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		582,657
Financial instruments sold, but not yet purchased, at fair value				2,770
Level 2 [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		1,853	[6]	15,053	[7]
Financial instruments sold, but not yet purchased, at fair value	[8]	36
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned				91,788
Available-for-sale securities		0
Investments		63,533		54,623
Derivative Assets	[2]	0
Total Assets		135,600		146,411
Financial instruments sold, but not yet purchased, at fair value		5,781
Derivative contracts, Liabilities	[4]	0
Total Liabilities		5,781
Level 3 [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		2,179		64,706
Level 3 [Member] | Corporate Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned				225
Investments		11,878		5,754
Level 3 [Member] | Auction Rate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		14,681		13,032
Level 3 [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		36,974		35,837
Level 3 [Member] | Sovereign Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		72,067
Level 3 [Member] | Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		69,888	[6]	$ 26,857	[7]
Financial instruments sold, but not yet purchased, at fair value	[8]	$ 5,781

[1] Due to the immaterial amount of income recognized on tax-exempt securities, yields were not calculated on a tax-equivalent basis.

[2] Included in other assets in the consolidated statements of financial condition

[3] Included in other assets in the consolidated statements of financial condition.

[4] Included in accounts payable and accrued expenses in the consolidated statements of financial condition.

[5] Included in accounts payable and accrued expenses in the consolidated statements of financial condition.

[6] Includes syndicated loans, non-agency mortgage-backed securities, and sovereign debt.

[7] Includes syndicated loans, non-agency mortgage-backed securities, and sovereign debt.

[8] Includes syndicated loans and state and municipal securities.