v3.26.3
Fair Value of Financial Instruments - Valuation of Financial Instruments by Pricing Observability Levels (Details) - USD ($)
Sep. 30, 2026
Dec. 31, 2025
Assets    
Convertible securities $ 128,934,000 $ 140,306,000
Equity securities 492,000 0
Fixed income securities 2,783,000 2,831,000
Taxable securities 26,238,000 33,021,000
Tax-exempt securities 139,263,000 125,419,000
Short-term securities 88,973,000 19,531,000
Asset-backed securities 60,981,000 92,472,000
U.S. government agency securities 51,928,000 82,666,000
U.S. government securities 7,705,000 201,000
Derivative contracts 3,401,000 5,823,000
Total financial instruments and other inventory positions owned 510,698,000 502,270,000
Liabilities    
Equity securities 19,923,000 0
Fixed income securities 2,535,000 3,300,000
U.S. government securities 39,303,000 43,403,000
Derivative contracts 758,000 1,811,000
Total financial instruments and other inventory positions sold, but not yet purchased 62,519,000 48,514,000
Securities posted as collateral 0 0
Measured on a recurring basis    
Assets    
Convertible securities 128,934,000 140,306,000
Equity securities 492,000  
Fixed income securities 2,783,000 2,831,000
Taxable securities 26,238,000 33,021,000
Tax-exempt securities 139,263,000 125,419,000
Short-term securities 88,973,000 19,531,000
Asset-backed securities 60,981,000 92,472,000
U.S. government agency securities 51,928,000 82,666,000
U.S. government securities 7,705,000 201,000
Derivative contracts 3,401,000 5,823,000
Total financial instruments and other inventory positions owned 510,698,000 502,270,000
Cash equivalents 548,637,000 717,600,000
Investments at fair value 272,057,000 305,473,000
Total assets 1,331,392,000 1,525,343,000
Derivative asset contracts - counterparty and collateral netting (24,539,000) (2,273,000)
Liabilities    
Equity securities 19,923,000  
Fixed income securities 2,535,000 3,300,000
U.S. government securities 39,303,000 43,403,000
Derivative contracts 758,000 1,811,000
Total financial instruments and other inventory positions sold, but not yet purchased 62,519,000 48,514,000
Derivative liability contracts - counterparty and cash collateral netting (13,728,000) (8,762,000)
Measured on a recurring basis | Investments attributable to noncontrolling interests    
Assets    
Investments at fair value 184,300,000 216,800,000
Measured on a recurring basis | Level I    
Assets    
Equity securities 270,000  
U.S. government securities 7,705,000 201,000
Total financial instruments and other inventory positions owned 7,975,000 201,000
Cash equivalents 548,637,000 717,600,000
Investments at fair value 72,213,000 87,507,000
Total assets 628,825,000 805,308,000
Liabilities    
Equity securities 19,923,000  
U.S. government securities 39,303,000 43,403,000
Total financial instruments and other inventory positions sold, but not yet purchased 59,226,000 43,403,000
Measured on a recurring basis | Level II    
Assets    
Convertible securities 128,934,000 140,306,000
Equity securities 222,000  
Fixed income securities 2,783,000 2,831,000
Taxable securities 26,238,000 33,021,000
Tax-exempt securities 139,263,000 125,419,000
Short-term securities 88,973,000 19,531,000
Asset-backed securities 60,981,000 92,472,000
U.S. government agency securities 51,928,000 82,666,000
Derivative contracts 3,411,000 5,744,000
Total financial instruments and other inventory positions owned 502,733,000 501,990,000
Total assets 502,733,000 501,990,000
Liabilities    
Fixed income securities 2,535,000 3,300,000
Derivative contracts 1,535,000 4,039,000
Total financial instruments and other inventory positions sold, but not yet purchased 4,070,000 7,339,000
Measured on a recurring basis | Level III    
Assets    
Derivative contracts 24,529,000 2,352,000
Total financial instruments and other inventory positions owned 24,529,000 2,352,000
Investments at fair value 199,844,000 217,966,000
Total assets 224,373,000 220,318,000
Liabilities    
Derivative contracts 12,951,000 6,534,000
Total financial instruments and other inventory positions sold, but not yet purchased 12,951,000 6,534,000
Measured on a recurring basis | Level III | Investments attributable to noncontrolling interests    
Assets    
Investments at fair value $ 158,800,000 $ 171,800,000