Postretirement Benefit Plans - Changes in Fair Value of Plan Assets of Pension and Other Employee-Related Defined Benefit Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in plan assets
Plan assets – January 1	$ 326.7	$ 269.2
Actual return on plan assets	(16.9)	46.4
Employer contributions	11.2	45.0
Benefits and expenses paid	(33.4)	(33.6)
Settlement	(6.3)	(0.4)
Foreign currency translation	0.0	0.1
Plan assets – December 31	281.3	326.7	$ 269.2
Funded status at end of year	(218.5)	(230.4)
Other Postretirement Benefits Plan [Member]
Change in plan assets
Plan assets – January 1	5.2	6.1
Actual return on plan assets	(0.1)	1.2
Employer contributions	6.9	6.1
Benefits and expenses paid	(9.1)	(8.2)
Settlement	0.0	0.0
Foreign currency translation	0.0	0.0
Plan assets – December 31	2.9	5.2	6.1
Funded status at end of year	(115.7)	(132.9)
Pension Plan [Member]
Change in plan assets
Plan assets – January 1	321.5
Plan assets – December 31	278.4	321.5
Funded status at end of year	(102.8)	(97.5)
Pension Plan [Member] | International Plan [Member]
Change in plan assets
Plan assets – January 1	0.6	0.9
Actual return on plan assets	0.0	0.0
Employer contributions	3.4	3.0
Benefits and expenses paid	(3.0)	(3.0)
Settlement	(0.4)	(0.4)
Foreign currency translation	0.0	0.1
Plan assets – December 31	0.6	0.6	0.9
Funded status at end of year	(88.8)	(92.7)
Pension Plan [Member] | U.S. Plan [Member]
Change in plan assets
Plan assets – January 1	320.9	262.2
Actual return on plan assets	(16.8)	45.2
Employer contributions	0.9	35.9
Benefits and expenses paid	(21.3)	(22.4)
Settlement	(5.9)	0.0	(28.0)
Foreign currency translation	0.0	0.0
Plan assets – December 31	277.8	320.9	$ 262.2
Funded status at end of year	$ (14.0)	$ (4.8)