ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	$ 755.3	$ 677.2
Amortization of prior service cost	(1.1)	(1.3)
Amortization of net loss	0.9	1.3
Other adjustments		0.2
Balance at the end of the period	763.0	681.4
Pensions
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(55.8)	(40.6)
Reclassification adjustment related to the Tax Act		(9.2)
Amortization of prior service cost	(0.4)	(0.4)
Amortization of net loss	0.7	0.9
Balance at the end of the period	(55.5)	(49.3)
Post Retirement
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	21.7	15.6
Reclassification adjustment related to the Tax Act		3.4
Amortization of prior service cost	(0.7)	(0.9)
Amortization of net loss	0.2	0.3
Balance at the end of the period	21.2	18.4
Non-Qualified Plans
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(0.1)	(0.3)
Reclassification adjustment related to the Tax Act		(0.2)
Amortization of net loss		0.1
Balance at the end of the period	(0.1)	(0.4)
Other
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(0.3)	0.4
Other adjustments		0.2
Balance at the end of the period	(0.3)	0.6
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(34.5)	(24.9)
Reclassification adjustment related to the Tax Act		(6.0)
Amortization of prior service cost	(1.1)	(1.3)
Amortization of net loss	0.9	1.3
Other adjustments		0.2
Balance at the end of the period	$ (34.7)	$ (30.7)