Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)	$ 11.2
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning Balance		$ 17.2	$ 20.3	$ 7.1
Charge to Expenses		1.9	(0.2)	16.4
Charged (credited) to other accounts		(12.4)	(2.1)	(0.3)
Deductions		(0.8)	(0.8)	(2.9)
Balance at end of period		5.9	17.2	20.3
SEC Schedule, 12-09, Allowance, Credit Loss [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning Balance			20.3
Balance at end of period				20.3
Tax Valuation Allowance [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning Balance		384.8	335.0	234.4
Additions Charged to Income		47.3	65.6	124.2
Additions Charged to Equity		6.6	(15.8)	(23.6)
Deductions		0.0	0.0	0.0
Balance at end of period		$ 438.7	$ 384.8	$ 335.0