Significant Accounting Policies - Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Equity [Abstract]
Balance at beginning of period, Pension and Postretirement Benefit Plans	$ 79.5	$ 87.9	$ 69.7	$ 89.4
Tax effect of other comprehensive loss (earnings)	(1.6)	(0.8)	8.2	(2.3)
Balance at end of period, Pension and Postretirement Benefit Plans	$ 77.9	$ 87.1	$ 77.9	$ 87.1