Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2021	Sep. 07, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (27.2)	$ (81.3)	$ (55.6)	$ (66.6)
Other comprehensive income (loss), net of tax:
Foreign currency translation (loss) gain	(1.4)	1.2	2.2	3.7
Cash flow hedges:
Unrealized loss on cash flow hedges arising during the period, net of tax of $0.0, ($3.4), ($3.7)	0.0	(0.1)	(11.4)	(12.5)
Reclassification adjustment for net losses included in net income, net of tax of $5.8, $2.0, $0.5	0.0	19.7	6.4	1.7
Defined benefit plans:
Net gain (loss) arising from remeasurement during the period, net of tax of $0.8, $1.8, ($0.8), $0.7	2.6	6.0	(2.7)	2.5
Amortization of prior service benefits included in net income, net of tax of ($0.4), ($0.6), ($0.6)	0.0	(1.3)	(1.9)	(1.9)
Amortization of net actuarial loss included in net income, net of tax of $3.6, $4.4, $3.6	0.0	12.0	14.9	11.9
Reclassification adjustment for pension settlement charges included in net income, net of tax of $0.9	0.0	0.0	2.9	0.0
Total other comprehensive income, net of tax	1.2	37.5	10.4	5.4
Total comprehensive loss	$ (26.0)	$ (43.8)	$ (45.2)	$ (61.2)