Fair Value Of Financial Instruments (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) - USD ($) $ in Thousands		Dec. 31, 2024		Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		$ 1,169,008		$ 918,741
Available-for-sale securities		1,584,598	[1]	1,551,686
Financial instruments sold, but not yet purchased, at fair value		646,271		497,741
U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	[1]	2,266
Corporate Fixed Income Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	[1]	463,992
State and Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	[1]	2,349
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		921,563	[1]	746,170
Agency Mortgage-Backed Securities [Member] | Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		67,956	[1]	66,671
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		199	[1]	261
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,584,598		1,551,686
Investments		75,358		91,105
Derivative contracts, Assets		110,814	[2]	118,668	[3]
Cash equivalents measured at NAV		1,932		4,706
Total Assets		2,941,710		2,684,906
Financial instruments sold, but not yet purchased, at fair value		646,271		497,741
Derivative contracts, Liabilities		110,825	[4]	118,651	[5]
Total Liabilities		757,096		616,392
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		20,045		32,411
Financial instruments sold, but not yet purchased, at fair value		370,373		273,653
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		149,479		106,634
Available-for-sale securities		2,266		2,219
Financial instruments sold, but not yet purchased, at fair value				4,924
Fair Value, Recurring [Member] | Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		113,033		19,604
Available-for-sale securities		126,273		177,853
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		274,207		237,671
Available-for-sale securities		463,992		556,161
Financial instruments sold, but not yet purchased, at fair value		174,425		138,359
Fair Value, Recurring [Member] | Corporate Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		50,787		52,520
Investments		30,227		22,406
Financial instruments sold, but not yet purchased, at fair value		34,437		21,576
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		229,342		223,155
Available-for-sale securities		2,349		2,351
Fair Value, Recurring [Member] | Auction Rate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		558		783
Fair Value, Recurring [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		14,378	[6]	39,655	[7]
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		30,195		28,261
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		2,939,778		2,680,200
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		262,629		159,903
Available-for-sale securities		921,563		746,170
Financial instruments sold, but not yet purchased, at fair value		65,946		52,664
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		67,956		66,671
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		199		261
Sovereign Debt [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		1,169,008		918,741
Other [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial instruments owned		69,486	[8]	86,843	[9]
Financial instruments sold, but not yet purchased, at fair value		1,090	[10]	6,565	[11]
Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		14,691		10,386
Total Assets		85,715		95,165
Financial instruments sold, but not yet purchased, at fair value		404,810		295,229
Total Liabilities		404,810		295,229
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		20,045		32,411
Financial instruments sold, but not yet purchased, at fair value		370,373		273,653
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		507		210
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		50,472		52,158
Investments		14,661		10,313
Financial instruments sold, but not yet purchased, at fair value		34,437		21,576
Level 1 [Member] | Fair Value, Recurring [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		30	[6]	73	[7]
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		71,024		84,779
Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		1,584,598		1,551,686
Investments		1		330
Derivative contracts, Assets		110,814	[2]	118,668	[3]
Total Assets		2,733,896		2,420,184
Financial instruments sold, but not yet purchased, at fair value		240,371		198,676
Derivative contracts, Liabilities		110,825	[4]	118,651	[5]
Total Liabilities		351,196		317,327
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		149,479		106,634
Available-for-sale securities		2,266		2,219
Financial instruments sold, but not yet purchased, at fair value				4,924
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		111,999		18,106
Available-for-sale securities		126,273		177,853
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		273,700		237,461
Available-for-sale securities		463,992		556,161
Financial instruments sold, but not yet purchased, at fair value		174,425		138,359
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		315		362
Investments		1		215
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		229,342		223,155
Available-for-sale securities		2,349		2,351
Level 2 [Member] | Fair Value, Recurring [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	[7]			115
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		262,629		159,903
Available-for-sale securities		921,563		746,170
Financial instruments sold, but not yet purchased, at fair value		65,946		52,664
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		67,956		66,671
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		199		261
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		1,038,483		749,500
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		11,019	[8]	3,879	[9]
Financial instruments sold, but not yet purchased, at fair value	[10]			2,729
Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		30,471		52,128
Total Assets		89,972		136,590
Financial instruments sold, but not yet purchased, at fair value		1,090		3,836
Total Liabilities		1,090		3,836
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		1,498
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		15,565		11,878
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		558		783
Level 3 [Member] | Fair Value, Recurring [Member] | Other Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		14,348	[6]	39,467	[7]
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		59,501		84,462
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		58,467	[8]	82,964	[9]
Financial instruments sold, but not yet purchased, at fair value	[10]	$ 1,090		$ 3,836

[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] Primarily includes private company investments.

[7] Primarily includes private company investments.

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

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

[10] Includes syndicated loans.

[11] Includes syndicated loans, state and municipal securities, and asset-backed securities.