Long-Term Debt - Aggregate Maturities of Long-Term Debt (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
2024	$ 0.7
2025	536.7
2026	0.8
2027	0.8
2028	0.9
2029 and thereafter	8.2
Subtotal	548.1
Less amounts representing original issue discount and debt issuance costs	1.6
Total debt	546.5	$ 559.5
After the effect of the exchange of Old Notes and issuance of New notes and Contran Term Loan
Debt Instrument [Line Items]
2024	0.7
2025	177.2
2026	0.8
2027	0.8
2028	0.9
2029 and thereafter	369.0
Subtotal	549.4
Less amounts representing original issue discount and debt issuance costs	6.1
Total debt	$ 543.3