v3.22.2.2
Retirement and Other Employee Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2022
Sep. 30, 2021
Sep. 30, 2022
Sep. 30, 2021
Pension Plan | Qualified Pension Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost $ 4.1 $ 3.5 $ 12.5 $ 10.5
Expected return on plan assets (6.9) (6.8) (20.7) (20.6)
Amortization of prior service credit 0.0 0.0 0.0 0.0
Amortization of net loss (gain) 0.8 1.2 2.3 3.6
Settlement loss 0.0 0.0 0.0 0.0
Net periodic benefit cost (2.0) (2.1) (5.9) (6.5)
Pension Plan | Unfunded Nonqualified  Pension Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost 0.3 0.3 1.0 0.9
Expected return on plan assets 0.0 0.0 0.0 0.0
Amortization of prior service credit 0.0 0.0 0.0 0.0
Amortization of net loss (gain) 0.5 0.8 1.6 2.4
Settlement loss 1.8 0.3 1.8 0.3
Net periodic benefit cost 2.6 1.4 4.4 3.6
Retirement Health Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Interest cost 0.0 0.1 0.1 0.1
Expected return on plan assets (0.3) (0.4) (1.0) (1.2)
Amortization of prior service credit (3.4) (3.4) (10.2) (10.2)
Amortization of net loss (gain) (0.2) (0.2) (0.6) (0.4)
Settlement loss 0.0 0.0 0.0 0.0
Net periodic benefit cost $ (3.9) $ (3.9) $ (11.7) $ (11.7)