v3.25.2
Variable and voting interest entities - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2024
Jun. 30, 2025
Jul. 31, 2026
Dec. 31, 2024
Variable Interest Entity [Line Items]        
Assets   $ 12,355.7   $ 12,524.9
Liabilities   10,248.9   10,586.1
Related Party Fund - Third Point Venture Offshore Fund I LP        
Variable Interest Entity [Line Items]        
Unfunded commitments   7.1   9.3
Related Party Fund - Third Point Venture Offshore Fund II LP        
Variable Interest Entity [Line Items]        
Unfunded commitments   18.2   19.7
Related Party Fund - Investment in Third Point Insurance Solutions Fund I LLC | Subsequent event | Forecast        
Variable Interest Entity [Line Items]        
Purchase of securities     $ 25.0  
Alstead Re        
Variable Interest Entity [Line Items]        
Assets   6.2   6.3
Liabilities   $ 0.6   0.8
Arcadian        
Variable Interest Entity [Line Items]        
Estimated fair value of retained noncontrolling interest $ 115.0      
Gain on deconsolidation $ 95.9      
VIE, ownership percentage   49.00%    
Alta Signa        
Variable Interest Entity [Line Items]        
Assets   $ 2.7   1.8
Liabilities   $ 1.6   $ 0.8
VOE, ownership percentage   75.10%    
TP Enhanced Fund | TP Enhanced Fund        
Variable Interest Entity [Line Items]        
VIE, ownership percentage   89.10%    
Variable interest entity, primary beneficiary | TP Enhanced Fund | TP GP        
Variable Interest Entity [Line Items]        
VIE, ownership percentage   10.90%