Retirement Plans, Postretirement and Postemployment Benefits - Change in Projected Benefit Obligation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension
Defined Benefit Plan Disclosure [Line Items]
Net projected benefit obligation at beginning of year	$ 1,111.9	$ 977.8
Service cost	46.2	39.2	$ 30.8
Interest cost	35.7	37.1	37.6
Actuarial (gain) loss	(16.2)	104.0
Gross benefits paid	(42.1)	(46.2)
Net projected benefit obligation at end of year	1,135.5	1,111.9	977.8
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net projected benefit obligation at beginning of year	12.6	13.0
Service cost			0.1
Interest cost	0.3	0.4	0.6
Participants' contributions	0.6	0.7
Actuarial (gain) loss	(0.6)	0.5
Gross benefits paid	(1.5)	(2.0)
Net projected benefit obligation at end of year	$ 11.4	$ 12.6	$ 13.0