v3.26.1
Employee and Agent Benefits - Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Pension benefits        
Components of Net Periodic Benefit Cost (Income)        
Service cost $ 15.2 $ 15.0 $ 31.5 $ 29.7
Interest cost $ 43.0 $ 43.7 $ 86.3 $ 86.8
Interest cost, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Expected return on plan assets $ (45.9) $ (43.1) $ (91.8) $ (86.0)
Expected return on plan assets, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Amortization of prior service benefit $ (3.8) $ (3.7) $ (7.5) $ (7.5)
Amortization of prior service (benefit) cost, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Recognized net actuarial (gain) loss $ 6.6 $ 9.1 $ 13.3 $ 17.4
Recognized net actuarial (gain) loss, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Settlement     $ 2.6  
Settlement, location on consolidated statements of operations     Operating expenses  
Net periodic benefit cost (income) $ 15.1 $ 21.0 $ 34.4 $ 40.4
Other postretirement benefits        
Components of Net Periodic Benefit Cost (Income)        
Interest cost $ 0.7 $ 0.7 $ 1.4 $ 1.5
Interest cost, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Expected return on plan assets $ (1.3) $ (1.2) $ (2.5) $ (2.3)
Expected return on plan assets, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Amortization of prior service benefit $ (0.2) $ (0.3) $ (0.5) $ (0.6)
Amortization of prior service (benefit) cost, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Recognized net actuarial (gain) loss $ (0.5) $ (0.3) $ (1.0) $ (0.7)
Recognized net actuarial (gain) loss, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Net periodic benefit cost (income) $ (1.3) $ (1.1) $ (2.6) $ (2.1)