Accounting Policies - Components of Changes in Accumulated Other Comprehensive Loss and Related Cumulative Noncurrent Deferred Tax Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 5,893.3	$ 5,353.3	$ 4,949.4
Other comprehensive (loss) earnings before reclassifications, net of Tax	51.6	(26.0)	(13.3)
Amounts reclassified from accumulated other comprehensive loss, net of tax	9.2	13.4	11.1
Other comprehensive (loss) earnings, net of tax	60.8	(12.6)	(2.2)
Ending Balance	6,537.6	5,893.3	5,353.3
Cumulative noncurrent deferred tax assets at end of period	69.7	89.4	85.2
Pension and Postretirement Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(158.1)	(144.9)	(141.5)
Other comprehensive (loss) earnings before reclassifications, net of Tax	51.3	(26.6)	(14.5)
Amounts reclassified from accumulated other comprehensive loss, net of tax	9.2	13.4	11.1
Other comprehensive (loss) earnings, net of tax	60.5	(13.2)	(3.4)
Ending Balance	(97.6)	(158.1)	(144.9)
Cumulative noncurrent deferred tax assets at end of period	69.7	89.4	85.2
Foreign Currency
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(0.3)	(0.9)	(2.1)
Other comprehensive (loss) earnings before reclassifications, net of Tax	0.3	0.6	1.2
Other comprehensive (loss) earnings, net of tax	0.3	0.6	1.2
Ending Balance		(0.3)	(0.9)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(158.4)	(145.8)	(143.6)
Ending Balance	$ (97.6)	$ (158.4)	$ (145.8)