STOCKHOLDERS' EQUITY - AOCI Reclassifications (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Amortization of pension and other post-retirement liability adjustments
Other income, net									$ 3.8	$ 9.6	$ 7.7
Pension settlement charges									21.0	5.7	2.2
Income before income tax expense (benefit)									90.9	98.2	78.6
Tax (benefit)									23.4	24.9	(1.6)
Net earnings	$ 10.3	$ 17.5	$ 21.7	$ 18.0	$ 24.6	$ 20.3	$ 13.1	$ 15.3	67.5	73.3	80.2
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Including Portion Attributable to Noncontrolling Interest | Amounts reclassified from accumulated other comprehensive income (loss)
Amortization of pension and other post-retirement liability adjustments
Other income, net									0.7	0.7	1.5
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest | Amounts reclassified from accumulated other comprehensive income (loss)
Amortization of pension and other post-retirement liability adjustments
Other income, net									(0.9)	(0.9)	(0.7)
Accumulated Defined Benefit Plans Adjustment, Pension Settlement Charge IncludingPortion Attributable to Noncontrolling Interest | Amounts reclassified from accumulated other comprehensive income (loss)
Amortization of pension and other post-retirement liability adjustments
Pension settlement charges									(20.8)	(5.7)	(2.2)
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest | Amounts reclassified from accumulated other comprehensive income (loss)
Amortization of pension and other post-retirement liability adjustments
Income before income tax expense (benefit)									(21.0)	(5.9)	(1.4)
Tax (benefit)									(5.5)	(1.5)	(0.6)
Net earnings									$ (15.5)	$ (4.4)	$ (0.8)