v3.26.1
Investments - Debt Securities (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Debt securities, available for sale    
Cost or amortized cost $ 5,180.5 $ 5,118.3
Gross unrealized gains 23.8 66.2
Gross unrealized losses (46.6) (13.3)
Net foreign currency gains (losses) (0.8) (2.6)
Fair value 5,156.9 5,168.6
Debt securities, trading    
Cost or amortized cost 88.6 114.6
Gross unrealized gains 0.1 0.5
Gross unrealized losses (23.9) (24.8)
Net foreign currency gains (losses) 0.0 0.0
Fair value 64.8 90.3
Asset-backed securities    
Debt securities, available for sale    
Cost or amortized cost 853.3 917.1
Gross unrealized gains 3.2 7.3
Gross unrealized losses (13.6) (3.3)
Net foreign currency gains (losses) 0.0 0.0
Fair value 842.9 921.1
Debt securities, trading    
Cost or amortized cost 7.8 8.3
Gross unrealized gains 0.0 0.0
Gross unrealized losses (2.7) (2.4)
Net foreign currency gains (losses) 0.0 0.0
Fair value 5.1 5.9
Residential mortgage-backed securities    
Debt securities, available for sale    
Cost or amortized cost 960.7 950.1
Gross unrealized gains 8.8 17.7
Gross unrealized losses (9.5) (4.7)
Net foreign currency gains (losses) 0.0 0.0
Fair value 960.0 963.1
Debt securities, trading    
Cost or amortized cost 31.4 50.7
Gross unrealized gains 0.1 0.1
Gross unrealized losses (4.5) (5.8)
Net foreign currency gains (losses) 0.0 0.0
Fair value 27.0 45.0
Commercial mortgage-backed securities    
Debt securities, available for sale    
Cost or amortized cost 256.5 231.3
Gross unrealized gains 1.2 3.1
Gross unrealized losses (1.6) (2.5)
Net foreign currency gains (losses) 0.0 0.0
Fair value 256.1 231.9
Debt securities, trading    
Cost or amortized cost 29.6 34.6
Gross unrealized gains 0.0 0.4
Gross unrealized losses (3.2) (3.1)
Net foreign currency gains (losses) 0.0 0.0
Fair value 26.4 31.9
Corporate debt securities    
Debt securities, available for sale    
Cost or amortized cost 2,242.5 2,170.8
Gross unrealized gains 9.6 32.3
Gross unrealized losses (13.7) (2.4)
Net foreign currency gains (losses) (1.2) (2.5)
Fair value 2,237.2 2,198.2
Debt securities, trading    
Cost or amortized cost 16.8 17.1
Gross unrealized gains 0.0 0.0
Gross unrealized losses (13.4) (13.4)
Net foreign currency gains (losses) 0.0 0.0
Fair value 3.4 3.7
U.S. government and government agency    
Debt securities, available for sale    
Cost or amortized cost 847.8 830.5
Gross unrealized gains 0.9 5.6
Gross unrealized losses (8.1) (0.4)
Net foreign currency gains (losses) 0.0 0.0
Fair value 840.6 835.7
Debt securities, trading    
Cost or amortized cost 3.0 3.9
Gross unrealized gains 0.0 0.0
Gross unrealized losses (0.1) (0.1)
Net foreign currency gains (losses) 0.0 0.0
Fair value 2.9 3.8
Non-U.S. government and government agency    
Debt securities, available for sale    
Cost or amortized cost 19.7 18.5
Gross unrealized gains 0.1 0.2
Gross unrealized losses (0.1) 0.0
Net foreign currency gains (losses) 0.4 (0.1)
Fair value $ 20.1 $ 18.6