Annual report pursuant to Section 13 and 15(d)

BENEFIT PLANS - Components of Net Periodic Benefit Cost (Details)

v3.20.4
BENEFIT PLANS - Components of Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]      
Recognized actuarial loss (gain) - mark to market $ 32.2 $ (4.8)  
Pension Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 1.7 2.8 $ 3.6
Interest cost 23.5 28.3 26.4
Expected return on plan assets (37.7) (34.3) (38.6)
Amortization of prior service cost (1.7) 0.5 0.5
Recognized actuarial loss (gain) - mark to market 30.4 0.2 7.7
Total net periodic benefit cost (income) 16.2 (2.5) (0.4)
Other Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 0.2 0.3 0.4
Interest cost 0.6 0.9 0.8
Expected return on plan assets (1.0) (0.9) (1.2)
Amortization of prior service cost (0.2) (1.0) (1.0)
Recognized actuarial loss (gain) - mark to market 1.8 (5.0) 0.4
Total net periodic benefit cost (income) $ 1.4 $ (5.7) $ (0.6)