v3.26.1
Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income, Net of Tax (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
AOCI:        
Beginning balance $ 5,869.4 $ 5,234.2 $ 5,871.6 $ 5,106.7
Change in accumulated other comprehensive income (loss) before reclassifications 20.1 97.2 (77.0) 169.5
Amounts reclassified from accumulated other comprehensive income (loss) 8.9 16.7 21.2 32.0
Total other comprehensive income (loss) 29.0 113.9 (55.8) 201.5
Ending balance 6,097.9 5,498.5 6,097.9 5,498.5
Accumulated Other Comprehensive Loss        
AOCI:        
Beginning balance (629.0) (748.5) (544.2) (836.1)
Ending balance (600.0) (634.6) (600.0) (634.6)
Foreign currency translation adjustment        
AOCI:        
Beginning balance (346.0) (406.4) (351.5) (415.2)
Change in accumulated other comprehensive income (loss) before reclassifications 8.5 43.9 14.0 52.7
Amounts reclassified from accumulated other comprehensive income (loss) 0.0 0.0 0.0 0.0
Total other comprehensive income (loss) 8.5 43.9 14.0 52.7
Ending balance (337.5) (362.5) (337.5) (362.5)
Net unrealized gains (losses) on investments        
AOCI:        
Beginning balance (152.6) (216.7) (63.0) (291.9)
Change in accumulated other comprehensive income (loss) before reclassifications 13.9 52.5 (87.8) 114.3
Amounts reclassified from accumulated other comprehensive income (loss) 8.8 16.7 20.9 30.1
Total other comprehensive income (loss) 22.7 69.2 (66.9) 144.4
Ending balance (129.9) (147.5) (129.9) (147.5)
Net unrealized gains on derivative transactions        
AOCI:        
Beginning balance 0.9 3.6 1.8 2.2
Change in accumulated other comprehensive income (loss) before reclassifications (2.6) 0.8 (3.1) 2.5
Amounts reclassified from accumulated other comprehensive income (loss) (0.5) (0.2) (0.9) (0.5)
Total other comprehensive income (loss) (3.1) 0.6 (4.0) 2.0
Ending balance (2.2) 4.2 (2.2) 4.2
Unamortized net losses on Pension Plans        
AOCI:        
Beginning balance (131.3) (129.0) (131.5) (131.2)
Change in accumulated other comprehensive income (loss) before reclassifications 0.3 0.0 (0.1) 0.0
Amounts reclassified from accumulated other comprehensive income (loss) 0.6 0.2 1.2 2.4
Total other comprehensive income (loss) 0.9 0.2 1.1 2.4
Ending balance $ (130.4) $ (128.8) $ (130.4) $ (128.8)