Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended	8 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 07, 2021	Sep. 30, 2020	Sep. 07, 2021	Sep. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (5.0)	$ (73.7)	$ (8.2)	$ (81.3)	$ (50.0)
Other comprehensive (loss) income, net of tax:
Foreign currency translation (loss) gain	(1.2)	(1.4)	2.0	1.2	(2.1)
Cash flow hedges:
Unrealized loss on cash flow hedges arising during the period, net of tax of ($0.2), ($0.1), $0.0, ($3.3)	0.0	(0.6)	(0.5)	(0.1)	(11.3)
Reclassification adjustment for net losses included in net income, net of tax of $4.7, $0.5, $5.8, $1.4	0.0	16.2	1.8	19.7	4.6
Defined benefit plans:
Net gain (loss) arising from remeasurement during the period, net of tax of $1.0, $1.8, ($3.4)	0.0	0.0	3.2	6.0	(11.5)
Amortization of prior service benefits included in net income, net of tax of ($0.1), ($0.1), ($0.4), ($0.4)	0.0	(0.3)	(0.5)	(1.3)	(1.5)
Amortization of net actuarial loss included in net income, net of tax of $1.0, $1.1, $3.6, $3.3	0.0	3.1	3.7	12.0	11.1
Reclassification adjustment for pension settlement charges included in net income, net of tax of $0.2	0.0	0.0	0.0	0.0	0.9
Total other comprehensive (loss) income	(1.2)	17.0	9.7	37.5	(9.8)
Total comprehensive (loss) income	$ (6.2)	$ (56.7)	$ 1.5	$ (43.8)	$ (59.8)