Financial Instruments and Fair Value Disclosures - Fair Value and Related Carrying Values of Our Debt Instruments (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Second Lien Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	$ 550.4	$ 0.0
Carrying Value	550.0	0.0
Exit Term Loans [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0.0	91.1
Carrying Value	0.0	100.0
First Lien Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value	0.0	78.3
Carrying Value	$ 0.0	$ 85.3