Postretirement Benefit Plans - Changes in Projected Benefit Obligations of Pension and Other Employee-Related Defined Benefit Plans (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in benefit obligation
Benefit obligation – January 1		$ 525.4	$ 499.8
Service cost		2.3	2.1
Interest cost		10.7	16.6
Amendments		0.0	1.7
Actuarial loss(a)	[1]	52.3	45.0
Benefits paid		(28.4)	(38.7)
Acquired		0.0	0.5
Settlement		(328.5)	0.0
Foreign currency translation		9.0	(1.6)
Benefit obligation – December 31		242.8	525.4	$ 499.8
Pension Plan [Member]
Change in benefit obligation
Benefit obligation – January 1		408.8
Service cost		1.5	1.4	1.7
Interest cost		7.9	12.6	11.5
Benefit obligation – December 31		124.5	408.8
Other Postretirement Benefits Plan [Member]
Change in benefit obligation
Benefit obligation – January 1		116.6	118.6
Service cost		0.8	0.7	0.9
Interest cost		2.8	4.0	4.5
Amendments		0.0	1.7
Actuarial loss(a)		4.0	3.6
Benefits paid		(5.9)	(12.0)
Acquired		0.0	0.0
Settlement		0.0	0.0
Foreign currency translation		0.0	0.0
Benefit obligation – December 31		118.3	116.6	118.6
United States | Pension Plan [Member]
Change in benefit obligation
Benefit obligation – January 1		310.4	291.8
Service cost		0.0	0.2	0.4
Interest cost		6.9	11.1	10.1
Amendments		0.0	0.0
Actuarial loss(a)	[1]	45.0	31.0
Benefits paid		(18.9)	(23.7)
Acquired		0.0	0.0
Settlement		(327.9)	0.0
Foreign currency translation		0.0	0.0
Benefit obligation – December 31		15.5	310.4	291.8
International Plan [Member] | Pension Plan [Member]
Change in benefit obligation
Benefit obligation – January 1		98.4	89.4
Service cost		1.5	1.2	1.3
Interest cost		1.0	1.5	1.4
Amendments		0.0	0.0
Actuarial loss(a)		3.3	10.4
Benefits paid		(3.6)	(3.0)
Acquired		0.0	0.5
Settlement		(0.6)	0.0
Foreign currency translation		9.0	(1.6)
Benefit obligation – December 31		$ 109.0	$ 98.4	$ 89.4

[1] In 2020, the actuarial loss is primarily due to a decrease in discount rates in addition to the annuity premium in connection with the U.S. qualified pension plan termination. In 2019, the actuarial loss was primarily due to a reduction in the discount rate used to measure the benefit obligations.