Postretirement Benefit Plans - Other Changes in Plan Assets and Net Periodic Postretirement Cost Recognized in Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Net periodic postretirement cost
Service cost	$ 2.6	$ 3.7
Interest cost	16.0	16.5
Other Postretirement Benefits Plan [Member]
Net periodic postretirement cost
Service cost	0.9	0.8		$ 0.9
Interest cost	4.5	4.4		4.9
Expected return on plan assets(b)	(0.1)	(0.3)		(0.5)
Amortization of net actuarial loss	4.0	4.4		4.6
Amortization of prior service cost	(5.3)	(5.8)		(6.5)
Total net periodic postretirement cost	4.0	3.5		3.4
Other changes in plan assets and benefit obligations recognized in other comprehensive loss
Net actuarial loss (gain)	(15.6)	1.0		(1.9)
Prior service cost	0.0	0.5		0.0
Amortization of net actuarial loss	(4.0)	(4.4)		(4.6)
Amortization of prior service cost	5.3	5.8		6.5
Total change recognized in other comprehensive income	(14.3)	2.9		0.0
Total impact from net periodic postretirement cost and changes in other comprehensive income	(10.3)	6.4		3.4
Pension Plan [Member]
Net periodic postretirement cost
Service cost	1.7	2.9		2.9
Interest cost	11.5	12.1		13.4
Expected return on plan assets(b)	(15.8)	(15.2)	[1]	(17.6)	[1]
Amortization of net actuarial loss	5.8	7.6		7.8
Amortization of prior service cost	0.9	1.0		0.9
Net periodic postretirement cost	4.1	8.4		7.4
Curtailment or settlement charges	1.7	3.7		12.7
Total net periodic postretirement cost	5.8	12.1		20.1
Other changes in plan assets and benefit obligations recognized in other comprehensive loss
Net actuarial loss (gain)	16.2	(8.2)		6.1
Prior service cost	(0.1)	1.6		0.4
Amortization of net actuarial loss	(7.5)	(7.6)		(20.5)
Amortization of prior service cost	(0.9)	(4.7)		(0.9)
Foreign currency translation	(1.0)	2.9		(0.5)
Total change recognized in other comprehensive income	6.7	(16.0)		(15.4)
Total impact from net periodic postretirement cost and changes in other comprehensive income	12.5	(3.9)		4.7
International Plan [Member] | Pension Plan [Member]
Net periodic postretirement cost
Service cost	1.3	1.4		1.3
Interest cost	1.4	1.6		1.5
Expected return on plan assets(b)	0.0	0.0	[1]	0.0	[1]
Amortization of net actuarial loss	0.9	1.0		0.7
Amortization of prior service cost	0.0	0.0		0.0
Net periodic postretirement cost	3.6	4.0		3.5
Curtailment or settlement charges	0.0	0.0		0.0
Total net periodic postretirement cost	3.6	4.0		3.5
Other changes in plan assets and benefit obligations recognized in other comprehensive loss
Net actuarial loss (gain)	0.8	(0.3)		4.0
Prior service cost	(0.1)	0.0		0.4
Amortization of net actuarial loss	(0.9)	(1.0)		(0.7)
Amortization of prior service cost	0.0	0.0		0.0
Foreign currency translation	(1.0)	2.9		(0.5)
Total change recognized in other comprehensive income	(1.2)	1.6		3.2
Total impact from net periodic postretirement cost and changes in other comprehensive income	2.4	5.6		6.7
U.S. Plan [Member] | Pension Plan [Member]
Net periodic postretirement cost
Service cost	0.4	1.5		1.6
Interest cost	10.1	10.5		11.9
Expected return on plan assets(b)	(15.8)	(15.2)	[1]	(17.6)	[1]
Amortization of net actuarial loss	4.9	6.6		7.1
Amortization of prior service cost	0.9	1.0		0.9
Net periodic postretirement cost	0.5	4.4		3.9
Curtailment or settlement charges	1.7	3.7		12.7
Total net periodic postretirement cost	2.2	8.1		16.6
Other changes in plan assets and benefit obligations recognized in other comprehensive loss
Net actuarial loss (gain)	15.4	(7.9)		2.1
Prior service cost	0.0	1.6		0.0
Amortization of net actuarial loss	(6.6)	(6.6)		(19.8)
Amortization of prior service cost	(0.9)	(4.7)		(0.9)
Foreign currency translation	0.0	0.0		0.0
Total change recognized in other comprehensive income	7.9	(17.6)		(18.6)
Total impact from net periodic postretirement cost and changes in other comprehensive income	$ 10.1	$ (9.5)		$ (2.0)

[1] (b) Plan administrative expenses of $3.1 and $2.5 during the years ended December 31, 2017 and 2016, respectively, have been reclassified from the service cost component line to the expected return on plan assets component line to conform to the current year presentation.