ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	$ 815.5	$ 800.2	$ 805.7	$ 765.2	$ 763.0	$ 755.3	$ 805.7	$ 755.3
Amortization of prior service cost	(1.2)			(1.0)			(3.5)	(3.3)
Amortization of net loss (gain)	0.5			1.2			3.1	3.0
Other adjustments	0.2			(0.7)			(0.6)	(0.9)
Balance at the end of the period	891.8	815.5	800.2	797.7	765.2	763.0	891.8	797.7
Pensions
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(50.6)	(51.3)	(51.9)	(55.3)	(55.5)	(55.8)	(51.9)	(55.8)
Amortization of prior service cost	(0.4)	(0.4)	(0.5)	(0.4)	(0.5)	(0.4)
Amortization of net loss (gain)	0.3	1.1	1.1	1.6	0.7	0.7
Balance at the end of the period	(50.7)	(50.6)	(51.3)	(54.1)	(55.3)	(55.5)	(50.7)	(54.1)
Post Retirement
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	15.2	15.8	16.3	20.6	21.2	21.7	16.3	21.7
Amortization of prior service cost	(0.8)	(0.7)	(0.6)	(0.5)	(0.7)	(0.7)
Amortization of net loss (gain)	0.3	0.1	0.1	(0.4)	0.1	0.2
Balance at the end of the period	14.7	15.2	15.8	19.7	20.6	21.2	14.7	19.7
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)	(0.4)	(0.1)	(0.1)	(0.1)	(0.4)	(0.1)
Amortization of prior service cost			(0.1)	(0.1)	(0.1)
Amortization of net loss (gain)	(0.1)	0.1	0.1		0.1
Balance at the end of the period	(0.4)	(0.3)	(0.4)	(0.2)	(0.1)	(0.1)	(0.4)	(0.2)
Other
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(1.7)	(1.6)	(0.9)	(0.4)	(0.3)	(0.3)	(0.9)	(0.3)
Amortization of prior service cost					0.1
Foreign currency exchange		0.3	(0.5)
Other adjustments	0.1	(0.4)	(0.2)	(0.7)	(0.2)
Balance at the end of the period	(1.5)	(1.7)	(1.6)	(1.1)	(0.4)	(0.3)	(1.5)	(1.1)
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive loss by component, net of taxes
Balance at the beginning of the period	(37.4)	(37.5)	(36.9)	(35.2)	(34.7)	(34.5)	(36.9)	(34.5)
Amortization of prior service cost	(1.2)	(1.1)	(1.2)	(1.0)	(1.2)	(1.1)
Amortization of net loss (gain)	0.5	1.3	1.3	1.2	0.9	0.9
Foreign currency exchange		0.3	(0.5)
Other adjustments	0.1	(0.4)	(0.2)	(0.7)	(0.2)
Balance at the end of the period	$ (37.9)	$ (37.4)	$ (37.5)	$ (35.7)	$ (35.2)	$ (34.7)	$ (37.9)	$ (35.7)