ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	$ 678.2
Amortization of prior service cost	(1.3)	$ (0.4)
Amortization of net loss	1.3	0.9
Remeasurement adjustment related to the Tax Act	(3.3)
Other adjustments	0.2	0.2
Balance at the end of the period	682.4
Pensions
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(40.6)	(41.4)
Amortization of prior service cost	(0.4)	(0.4)
Amortization of net loss	0.9	0.8
Remeasurement adjustment related to the Tax Act	(9.2)
Balance at the end of the period	(49.3)	(41.0)
Post Retirement
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	15.6	18.1
Amortization of prior service cost	(0.9)
Amortization of net loss	0.3	0.1
Remeasurement adjustment related to the Tax Act	3.4
Balance at the end of the period	18.4	18.2
Non-Qualified Plans
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(0.3)	(0.4)
Amortization of net loss	0.1
Remeasurement adjustment related to the Tax Act	(0.2)
Balance at the end of the period	(0.4)	(0.4)
Other
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	0.4	0.1
Other adjustments	0.2	0.2
Balance at the end of the period	0.6	0.3
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(24.9)	(23.6)
Amortization of prior service cost	(1.3)	(0.4)
Amortization of net loss	1.3	0.9
Remeasurement adjustment related to the Tax Act	(6.0)
Other adjustments	0.2	0.2
Balance at the end of the period	$ (30.7)	$ (22.9)