PENSION AND POST-RETIREMENT PLANS - COMPONENTS OF NET PERIODIC BENEFIT COST (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pension Benefits
Components of Net Periodic Benefit Cost (Benefit):
Service cost	$ 1.1	$ 1.1	$ 3.3	$ 3.0
Interest cost	2.1	2.5	6.4	7.3
Expected return on plan assets	(3.3)	(3.3)	(10.1)	(10.1)
Amortization of net loss	1.0	1.3	3.4	3.8
Amortization of prior service credit	(0.5)	(0.6)	(1.7)	(1.7)
Other adjustments		0.1		0.1
Net periodic benefit cost	0.4	1.1	1.3	2.4
Post-retirement Benefits
Components of Net Periodic Benefit Cost (Benefit):
Service cost	0.2		0.5	0.4
Service cost		(0.4)
Interest cost	0.3		0.8	0.8
Interest cost		(0.6)
Amortization of net loss	0.3	0.3	1.1	0.9
Amortization of prior service credit	(1.0)	(2.8)	(2.8)	(2.8)
Net periodic benefit cost	$ (0.2)	$ (3.5)	$ (0.4)	$ (0.7)