PENSION AND OTHER POST-RETIREMENT PLANS - COMPONENTS OF NET PERIODIC BENEFIT COST (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Pension Benefits
Components of Net Periodic Benefit Costs:
Service cost	$ 3.0	$ 3.0
Interest cost	7.3	7.3
Expected return on plan assets	(10.1)	(10.0)
Amortization of net loss	3.8	4.1
Amortization of prior service cost	(1.7)	(1.7)
Other adjustments	0.1
Net periodic benefit cost	2.4	2.7
Defined Benefit Pension Plan Contributions
Employer contribution	3.0
Estimated future contributions to be made during the year	0.0
Other Post-retirement Benefits
Components of Net Periodic Benefit Costs:
Service cost	0.4	1.1
Interest cost	0.8	2.0
Amortization of net loss	0.9	0.9
Amortization of prior service cost	(2.8)
Net periodic benefit cost	$ (0.7)	$ 4.0