PENSION AND POST-RETIREMENT PLANS - COMPONENTS OF NET PERIODIC BENEFIT COST (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Components of Net Periodic Benefit Cost (Benefit):
Service cost	$ 1.2	$ 1.1
Interest cost	1.9	2.3
Expected return on plan assets	(3.2)	(3.1)
Amortization of net loss	1.5	0.9
Amortization of prior service credit	(0.6)	(0.6)
Net periodic benefit cost (benefit)	0.8	0.6
Post-retirement Benefits
Components of Net Periodic Benefit Cost (Benefit):
Service cost	0.1	0.1
Interest cost	0.2	0.3
Amortization of net loss	0.2	0.2
Amortization of prior service credit	(0.9)	(0.9)
Net periodic benefit cost (benefit)	$ (0.4)	$ (0.3)