Company's Liability for Environmental Obligations (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Environmental Exit Cost [Line Items]
Total Balance at Beginning of Period	$ 4.4	$ 2.7
Additions	0.7	0.4
Less: Payments / Reductions	0.5	0.3
Total Balance at End of Period	4.6	2.8
Less: Current Portion	0.6	0.6	$ 0.6
Noncurrent Balance at End of Period	$ 4.0	$ 2.2	$ 3.8