v3.26.1
Investments - Narrative (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
May 21, 2026
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Apr. 01, 2026
Dec. 31, 2025
Dec. 31, 2024
Net Investment Income [Line Items]                
Management fees   $ 15,643 $ 13,719 $ 30,112 $ 26,685      
Restricted cash and cash equivalents   111,631   111,631     $ 109,731  
Cash, cash equivalents and restricted cash   828,966 1,071,297 828,966 1,071,297   1,172,090 $ 1,100,852
Cash and cash equivalents   717,335   717,335     1,062,359  
Capital Requirements | Asset Pledged as Collateral                
Net Investment Income [Line Items]                
Investments, fair value   289,900   289,900     263,100  
Restricted cash and cash equivalents   2,500   2,500     1,400  
Trust Accounts | Asset Pledged as Collateral                
Net Investment Income [Line Items]                
Investments, fair value   294,600   294,600     265,000  
Restricted cash and cash equivalents   1,900   1,900     2,100  
Underwriting Obligations | Asset Pledged as Collateral                
Net Investment Income [Line Items]                
Investments, fair value   90,000   90,000     90,400  
Restricted cash and cash equivalents   107,200   107,200     106,200  
TS Hamilton Fund                
Net Investment Income [Line Items]                
Management fee percentage 2.50%              
Management fees   14,900 13,100 28,600 25,500      
Incentive allocation 30.00%              
Incentive allocation, reduction (as a percent) 50.00%              
Incentive allocation, cumulative net profits (as a percent) 200.00%              
Incentive allocation, excess profits (as a percent) 25.00%              
Incentive allocation, net profits (as a percent) 10.00%              
Incentive allocation expense (income)   111,000 $ 80,400 194,500 $ 180,700      
Cash and cash equivalents   $ 180,183   $ 180,183     $ 648,726  
TS Hamilton Fund | Hamilton Re | Sub-Series A Interests                
Net Investment Income [Line Items]                
Capital account withdrawal, notice period 55 days              
TS Hamilton Fund | Hamilton Re | Sub-Series B Interests                
Net Investment Income [Line Items]                
Capital account withdrawal, notice period 6 months              
Maximum monthly withdrawal           8.33%    
Two Sigma Hamilton Fund, LLC | Hamilton Re                
Net Investment Income [Line Items]                
Commitment for investment in Two Sigma Funds $ 1,800,000              
Investment in Two Sigma Funds, as a percentage of net tangible assets 60.00%