v3.26.1
Investments - Schedule of Changes in Other Investments (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Other Investments [Roll Forward]        
Balance, beginning of period $ 621.3 $ 526.3 $ 626.8 $ 539.0
Purchases and commitments funded 58.3 40.8 74.2 48.9
Sales and distributions (18.6) (17.0) (43.3) (41.8)
Net realized and unrealized gains (losses) 5.1 16.0 8.4 20.0
Balance, end of period 666.1 566.1 666.1 566.1
Debt Securities, Available-for-Sale [Roll Forward]        
Balance, beginning of period 0.0 0.0 0.0 0.0
Purchases and commitments funded 15.1 0.0 15.1 0.0
Sales and distributions 0.0 0.0 0.0 0.0
Net realized and unrealized gains (losses) (0.2) 0.0 (0.2) 0.0
Balance, end of period 14.9 0.0 14.9 0.0
Equity Securities Without Readily Determinable Fair Value [Roll Forward]        
Balance, beginning of period 50.4 50.4 50.4 50.4
Purchases and commitments funded 0.0 0.0 0.0 0.0
Sales and distributions 0.0 0.0 0.0 0.0
Net realized and unrealized gains (losses) 0.0 0.0 0.0 0.0
Balance, end of period 50.4 50.4 50.4 50.4
Fair Value Measured at NAV        
Other Investments [Roll Forward]        
Balance, beginning of period 570.9 475.9 576.4 488.6
Purchases and commitments funded 43.2 40.8 59.1 48.9
Sales and distributions (18.6) (17.0) (43.3) (41.8)
Net realized and unrealized gains (losses) 5.3 16.0 8.6 20.0
Balance, end of period $ 600.8 $ 515.7 $ 600.8 $ 515.7