Components of Change in Projected Benefit Obligation and Change in Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in projected benefit obligation:
Benefit obligation, beginning balance	$ 3,234.4	$ 2,655.4
Service cost	130.4	102.0	$ 108.3
Interest cost	83.0	95.6	85.8
Benefits paid	(120.2)	(127.0)
Actuarial loss	379.5	478.0
Currency translation and other	54.4	30.0
Participant contributions	0.4	0.4
Projected benefit obligation, ending balance	3,761.9	3,234.4	2,655.4
Change in plan assets:
Fair value of plan assets, beginning balance	3,226.4	2,699.2
Employer contributions	184.9	35.7
Actual return on plan assets	453.4	588.1
Benefits paid	(120.2)	(127.0)
Currency translation and other	48.5	30.0
Participant contributions	0.4	0.4
Fair value of plan assets, ending balance	3,793.4	3,226.4	$ 2,699.2
Funded status, ending balance	31.5	(8.0)
Amounts recorded on Balance Sheet:
Other noncurrent assets	222.1	146.5
Accounts payable, accrued expenses and other	25.5	39.9
Other liabilities	165.1	114.6
Accumulated other comprehensive loss:
Actuarial loss	571.7	512.5
Prior service cost	$ 6.3	5.1
Net initial transition amount		$ 0.1