ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Summary of Changes by Component (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications	$ (4.7)
Amounts reclassified from AOCL	3.2
Net current period other comprehensive income (loss) before income tax	(1.5)
Income tax expense	(2.8)
Other comprehensive income (loss)	(4.3)
Unrealized gains (losses) on Interest Rate Swaps
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(6.7)
Other comprehensive income (loss) before reclassifications	0.1
Amounts reclassified from AOCL	1.3
Net current period other comprehensive income (loss) before income tax	1.4
Income tax expense	(0.3)
Other comprehensive income (loss)	1.1
Ending balance	(5.6)
Foreign Currency Translation Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(7.9)
Other comprehensive income (loss) before reclassifications	(3.8)
Amounts reclassified from AOCL	0.0
Net current period other comprehensive income (loss) before income tax	(3.8)
Income tax expense	0.0
Other comprehensive income (loss)	(3.8)
Ending balance	(11.7)
Foreign Currency Translation Adjustment on Long-term Intercompany Notes
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	5.0
Other comprehensive income (loss) before reclassifications	(8.8)
Amounts reclassified from AOCL	0.0
Net current period other comprehensive income (loss) before income tax	(8.8)
Income tax expense	0.0
Other comprehensive income (loss)	(8.8)
Ending balance	(3.8)
Pension and Other Post-Employment Liability Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(36.2)
Other comprehensive income (loss) before reclassifications	7.8
Amounts reclassified from AOCL	1.9
Net current period other comprehensive income (loss) before income tax	9.7
Income tax expense	(2.5)
Other comprehensive income (loss)	7.2
Ending balance	(29.0)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(45.8)
Ending balance	$ (50.1)