ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Reclassification Adjustment (Details) - USD ($) $ in Millions	5 Months Ended	7 Months Ended	12 Months Ended
	Dec. 31, 2023	Aug. 12, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (68.7)	$ (178.0)	$ (199.2)	$ (195.3)
Miscellaneous, net	(0.8)	12.3	2.2	3.4
Net income (loss)	19.1	1,357.5	(585.6)	(78.1)
Income tax expense (benefit)	(14.7)	90.4	149.2	$ 27.7
Reclassifications
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	(6.0)	3.1	50.5
Reclassifications | Hedges | Interest rate swap
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	0.0	0.0	(0.6)
Income tax expense (benefit)			0.1
Reclassifications | Pension and Other Post-Retirement Benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Miscellaneous, net	(6.0)	3.1	51.1
Reclassifications | Net prior service benefit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Miscellaneous, net	0.4	(0.2)	2.4
Income tax expense (benefit)	(0.2)	0.2	0.0
Reclassifications | Net actuarial gains
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Miscellaneous, net	(6.5)	4.2	38.5
Income tax expense (benefit)	2.6	(4.9)	0.0
Reclassifications | Net actuarial gains (losses) due to settlement
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Miscellaneous, net	0.1	(0.9)	10.2
Income tax expense (benefit)	$ 0.0	$ 1.1	$ 0.0