Fair Value Of Financial Instruments (Fair Value of Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Thousands		Jun. 30, 2025		Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		$ 1,343,513		$ 1,169,008
Available-for-sale securities		1,546,392		1,584,598
Financial instruments sold, but not yet purchased, at fair value		819,555		646,271
U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		2,338
Corporate Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		434,137
State and Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		2,350
Agency Mortgage-Backed Securities [Member] | Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		948,159		921,563
Agency Mortgage-Backed Securities [Member] | Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		41,656		67,956
Agency Mortgage-Backed Securities [Member] | Non-Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		168		199
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,546,392		1,584,598
Investments		78,572		75,358
Derivative contracts, Assets		82,341	[1]	110,814	[2]
Cash equivalents measured at NAV		5,061		1,932
Total Assets		3,055,879		2,941,710
Financial instruments sold, but not yet purchased, at fair value		819,555		646,271
Derivative contracts, Liabilities		82,353	[3]	110,825	[4]
Total Liabilities		901,908		757,096
Fair Value, Recurring [Member] | U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		122,226		149,479
Available-for-sale securities		2,338		2,266
Fair Value, Recurring [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		113,938		113,033
Available-for-sale securities		117,584		126,273
Fair Value, Recurring [Member] | Corporate Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		285,451		274,207
Available-for-sale securities		434,137		463,992
Financial instruments sold, but not yet purchased, at fair value		137,127		174,425
Fair Value, Recurring [Member] | Corporate Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		59,147		50,787
Investments		31,953		30,227
Financial instruments sold, but not yet purchased, at fair value		31,361		34,437
Fair Value, Recurring [Member] | State and Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		213,226		229,342
Available-for-sale securities		2,350		2,349
Fair Value, Recurring [Member] | Auction Rate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		554		558
Fair Value, Recurring [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		13,641	[5]	14,378	[6]
Fair Value, Recurring [Member] | Investments in Funds and Partnerships Measured at NAV [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		32,424		30,195
Fair Value, Recurring [Member] | Assets At Fair Value On Recurring Basis Before Cash Equivalents Measured at NAV [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets		3,050,818		2,939,778
Fair Value, Recurring [Member] | U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		24,466		20,045
Financial instruments sold, but not yet purchased, at fair value		477,514		370,373
Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		476,953		262,629
Available-for-sale securities		948,159		921,563
Financial instruments sold, but not yet purchased, at fair value		171,839		65,946
Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		41,656		67,956
Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Non-Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		168		199
Sovereign Debt [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		1,343,513		1,169,008
Other [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		48,106	[7]	69,486	[8]
Financial instruments sold, but not yet purchased, at fair value		1,714	[9]	1,090	[10]
Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		14,879		14,691
Derivative contracts, Assets	[1]	0
Total Assets		98,505		85,715
Financial instruments sold, but not yet purchased, at fair value		508,875		404,810
Total Liabilities		508,875		404,810
Level 1 [Member] | Fair Value, Recurring [Member] | Corporate Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		33		507
Level 1 [Member] | Fair Value, Recurring [Member] | Corporate Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		59,127		50,472
Investments		14,878		14,661
Financial instruments sold, but not yet purchased, at fair value		31,361		34,437
Level 1 [Member] | Fair Value, Recurring [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		1	[5]	30	[6]
Level 1 [Member] | Fair Value, Recurring [Member] | U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		24,466		20,045
Financial instruments sold, but not yet purchased, at fair value		477,514		370,373
Level 1 [Member] | Sovereign Debt [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		83,626		71,024
Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,546,392		1,584,598
Investments		1		1
Derivative contracts, Assets		82,341	[1]	110,814	[2]
Total Assets		2,847,777		2,733,896
Financial instruments sold, but not yet purchased, at fair value		309,439		240,371
Derivative contracts, Liabilities		82,353	[3]	110,825	[4]
Total Liabilities		391,792		351,196
Level 2 [Member] | Fair Value, Recurring [Member] | U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		122,226		149,479
Available-for-sale securities		2,338		2,266
Level 2 [Member] | Fair Value, Recurring [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		112,904		111,999
Available-for-sale securities		117,584		126,273
Level 2 [Member] | Fair Value, Recurring [Member] | Corporate Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		285,418		273,700
Available-for-sale securities		434,137		463,992
Financial instruments sold, but not yet purchased, at fair value		137,127		174,425
Level 2 [Member] | Fair Value, Recurring [Member] | Corporate Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		20		315
Investments		1		1
Level 2 [Member] | Fair Value, Recurring [Member] | State and Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		213,226		229,342
Available-for-sale securities		2,350		2,349
Level 2 [Member] | Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		476,953		262,629
Available-for-sale securities		948,159		921,563
Financial instruments sold, but not yet purchased, at fair value		171,839		65,946
Level 2 [Member] | Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		41,656		67,956
Level 2 [Member] | Fair Value, Recurring [Member] | Agency Mortgage-Backed Securities [Member] | Non-Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		168		199
Level 2 [Member] | Sovereign Debt [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		1,219,043		1,038,483
Level 2 [Member] | Other [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		8,296	[7]	11,019	[8]
Financial instruments sold, but not yet purchased, at fair value	[9]	473
Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		31,268		30,471
Total Assets		72,112		89,972
Financial instruments sold, but not yet purchased, at fair value		1,241		1,090
Total Liabilities		1,241		1,090
Level 3 [Member] | Fair Value, Recurring [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		1,034		1,034
Level 3 [Member] | Fair Value, Recurring [Member] | Corporate Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		17,074		15,565
Level 3 [Member] | Fair Value, Recurring [Member] | Auction Rate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		554		558
Level 3 [Member] | Fair Value, Recurring [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		13,640	[5]	14,348	[6]
Level 3 [Member] | Sovereign Debt [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		40,844		59,501
Level 3 [Member] | Other [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		39,810	[7]	58,467	[8]
Financial instruments sold, but not yet purchased, at fair value		$ 1,241	[9]	$ 1,090	[10]

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

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

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

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

[5] Primarily includes private company investments.

[6] Primarily includes private company investments.

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

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

[9] Includes syndicated loans and sovereign debt.

[10] Includes syndicated loans.