v3.26.1
Fair Value of Financial Instruments - Valuation of Financial Instruments by Pricing Observability Levels (Details) - USD ($)
Jun. 30, 2026
Dec. 31, 2025
Assets    
Convertible securities $ 147,513,000 $ 140,306,000
Fixed income securities 9,677,000 2,831,000
Taxable securities 26,132,000 33,021,000
Tax-exempt securities 126,827,000 125,419,000
Short-term securities 39,095,000 19,531,000
Asset-backed securities 133,356,000 92,472,000
U.S. government agency securities 63,341,000 82,666,000
U.S. government securities 6,763,000 201,000
Derivative contracts 5,380,000 5,823,000
Total financial instruments and other inventory positions owned 558,084,000 502,270,000
Liabilities    
Equity securities 56,262,000 0
Fixed income securities 2,481,000 3,300,000
U.S. government securities 20,177,000 43,403,000
Derivative contracts 1,625,000 1,811,000
Total financial instruments and other inventory positions sold, but not yet purchased 80,545,000 48,514,000
Securities posted as collateral 0 0
Measured on a recurring basis    
Assets    
Convertible securities 147,513,000 140,306,000
Fixed income securities 9,677,000 2,831,000
Taxable securities 26,132,000 33,021,000
Tax-exempt securities 126,827,000 125,419,000
Short-term securities 39,095,000 19,531,000
Asset-backed securities 133,356,000 92,472,000
U.S. government agency securities 63,341,000 82,666,000
U.S. government securities 6,763,000 201,000
Derivative contracts 5,380,000 5,823,000
Total financial instruments and other inventory positions owned 558,084,000 502,270,000
Cash equivalents 270,026,000 717,600,000
Investments at fair value 285,887,000 305,473,000
Total assets 1,113,997,000 1,525,343,000
Derivative asset contracts - counterparty and collateral netting (3,570,000) (2,273,000)
Liabilities    
Equity securities 56,262,000  
Fixed income securities 2,481,000 3,300,000
U.S. government securities 20,177,000 43,403,000
Derivative contracts 1,625,000 1,811,000
Total financial instruments and other inventory positions sold, but not yet purchased 80,545,000 48,514,000
Derivative liability contracts - counterparty and cash collateral netting (6,230,000) (8,762,000)
Measured on a recurring basis | Investments attributable to noncontrolling interests    
Assets    
Investments at fair value 195,000,000.0 216,800,000
Measured on a recurring basis | Level I    
Assets    
U.S. government securities 6,763,000 201,000
Total financial instruments and other inventory positions owned 6,763,000 201,000
Cash equivalents 270,026,000 717,600,000
Investments at fair value 90,131,000 87,507,000
Total assets 366,920,000 805,308,000
Liabilities    
Equity securities 56,262,000  
U.S. government securities 20,177,000 43,403,000
Total financial instruments and other inventory positions sold, but not yet purchased 76,439,000 43,403,000
Measured on a recurring basis | Level II    
Assets    
Convertible securities 147,513,000 140,306,000
Fixed income securities 9,677,000 2,831,000
Taxable securities 26,132,000 33,021,000
Tax-exempt securities 126,827,000 125,419,000
Short-term securities 39,095,000 19,531,000
Asset-backed securities 133,356,000 92,472,000
U.S. government agency securities 63,341,000 82,666,000
Derivative contracts 4,894,000 5,744,000
Total financial instruments and other inventory positions owned 550,835,000 501,990,000
Total assets 550,835,000 501,990,000
Liabilities    
Fixed income securities 2,481,000 3,300,000
Derivative contracts 3,394,000 4,039,000
Total financial instruments and other inventory positions sold, but not yet purchased 5,875,000 7,339,000
Measured on a recurring basis | Level III    
Assets    
Derivative contracts 4,056,000 2,352,000
Total financial instruments and other inventory positions owned 4,056,000 2,352,000
Investments at fair value 195,756,000 217,966,000
Total assets 199,812,000 220,318,000
Liabilities    
Derivative contracts 4,461,000 6,534,000
Total financial instruments and other inventory positions sold, but not yet purchased 4,461,000 6,534,000
Measured on a recurring basis | Level III | Investments attributable to noncontrolling interests    
Assets    
Investments at fair value $ 154,400,000 $ 171,800,000