Pension Plans and Other Postretirement Benefits - Changes in Benefit Obligations, Fair Value, Funded Status (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Pension Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	$ 416.2	$ 321.9
Service cost	17.4	13.1	$ 12.3
Interest cost	3.4	5.1	4.9
Plan participants' contributions	1.8	1.9
Actuarial changes in assumptions and experience	32.9	45.7
Benefits paid (refunded)	(2.8)	0.1
Benefit payments by employer	(2.4)	(2.3)
Acquisitions		44.5
Curtailments	(3.3)	(3.8)
Settlements	(14.4)	(7.2)
Other	(0.1)	(0.1)
Currency impact	43.0	(2.7)
Benefit obligation at end of period	491.7	416.2	321.9
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of period	151.8	138.5
Actual return on plan assets	5.6	16.3
Settlements	(14.4)	(7.2)
Employer contributions	6.7	5.7
Plan participants' contributions	1.8	1.9
Benefits paid	(5.2)	(2.2)
Currency impact	14.6	(1.2)
Fair value of plan assets at end of period	160.9	151.8	138.5
Funded status at end of period	(330.8)	(264.4)
Other Postretirement Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of period	6.2	5.8
Service cost		0.1	0.2
Interest cost	0.2	0.2	0.2
Actuarial changes in assumptions and experience	0.3	0.1
Benefit obligation at end of period	6.7	6.2	$ 5.8
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Funded status at end of period	$ (6.7)	$ (6.2)