v3.25.2
Employee and Agent Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Pension benefits        
Components of Net Periodic Benefit Cost (Income)        
Service cost $ 15.0 $ 14.8 $ 29.7 $ 29.6
Interest cost $ 43.7 $ 40.5 $ 86.8 $ 80.8
Interest cost, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Expected return on plan assets $ (43.1) $ (42.6) $ (86.0) $ (85.2)
Expected return on plan assets, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Amortization of prior service benefit $ (3.7) $ (4.1) $ (7.5) $ (8.3)
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 $ 9.1 $ 9.8 $ 17.4 $ 19.4
Recognized net actuarial (gain) loss, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Net periodic benefit cost (income) $ 21.0 $ 18.4 $ 40.4 $ 36.3
Contributions made by employer to fund qualified and nonqualified pension plans 33.0   33.0  
Pension benefits | Maximum        
Components of Net Periodic Benefit Cost (Income)        
Amount of possible contributions to be made during the current fiscal year to the qualified and nonqualified pension plans combined 70.0   70.0  
Other postretirement benefits        
Components of Net Periodic Benefit Cost (Income)        
Interest cost $ 0.7 $ 0.7 $ 1.5 $ 1.5
Interest cost, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Expected return on plan assets $ (1.2) $ (1.2) $ (2.3) $ (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 $ (0.3) $ (0.2) $ (0.6) $ (0.5)
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 $ (0.3) $ (0.2) $ (0.7) $ (0.5)
Recognized net actuarial (gain) loss, location on consolidated statements of operations Operating expenses Operating expenses Operating expenses Operating expenses
Net periodic benefit cost (income) $ (1.1) $ (0.9) $ (2.1) $ (1.8)