Components of Change in Projected Benefit Obligation and Change in Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in projected benefit obligation:
Benefit obligation, beginning balance	$ 2,505.6	$ 2,306.0
Service cost	92.9	88.6	$ 91.3
Interest cost	81.1	94.3	92.2
Benefits paid	(82.6)	(80.2)
Actuarial loss	154.7	186.4
Currency translation and other	68.6	(90.6)
Participant contributions	0.4	1.1
Projected benefit obligation, ending balance	2,820.7	2,505.6	2,306.0
Change in plan assets:
Fair value of plan assets, beginning balance	2,494.1	2,219.0
Employer contributions	70.6	185.7
Actual return on plan assets	369.8	254.5
Benefits paid	(82.6)	(80.2)
Currency translation and other	67.3	(86.0)
Participant contributions	0.4	1.1
Fair value of plan assets, ending balance	2,919.6	2,494.1	$ 2,219.0
Funded status, ending balance	98.9	(11.5)
Amounts recorded on balance sheet:
Other noncurrent assets	228.9	107.2
Other liabilities	130.0	118.7
Accumulated other comprehensive loss:
Actuarial loss	372.9	410.6
Prior service cost	2.6	3.4
Net initial transition amount	$ 0.1	$ 0.1