v3.26.3
Equity Securities (Narrative) (Detail) - USD ($)
1 Months Ended 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Schedule Of Investments [Line Items]            
Realized and unrealized net gains on equity securities   $ 1,200,000 $ 38,700,000 $ 41,500,000 $ 57,800,000  
Net unrealized gains on equity securities   1,200,000 $ 35,700,000 38,800,000 $ 55,000,000  
Carrying values of equity method investments $ 146,100,000 146,100,000   146,100,000   $ 118,400,000
Secured Promissory Note | Affiliated Entity            
Schedule Of Investments [Line Items]            
Current borrowings 19,000,000 19,000,000   19,000,000    
Maximum borrowing capacity $ 25,000,000 $ 25,000,000   $ 25,000,000    
Debt instrument, term 6 years          
Stated interest rate 11.00% 11.00%   11.00%    
Nonconsolidated Variable Interest Entities            
Schedule Of Investments [Line Items]            
Carrying values of equity method investments $ 112,800,000 $ 112,800,000   $ 112,800,000   $ 86,800,000
Loss from equity method investments $ 125,400,000 $ 125,400,000   125,400,000    
Non-Marketable Equity Investment            
Schedule Of Investments [Line Items]            
Impairment loss       $ 41,700,000