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, 2019	Dec. 31, 2018	Dec. 31, 2017
Net periodic postretirement cost
Service cost	$ 2.1	$ 2.6
Interest cost	16.6	16.0
Other Postretirement Benefits Plan [Member]
Net periodic postretirement cost
Service cost	0.7	0.9	$ 0.8
Interest cost	4.0	4.5	4.4
Expected return on plan assets	(0.2)	(0.1)	(0.3)
Amortization of net actuarial loss	2.3	4.0	4.4
Amortization of prior service cost	(5.1)	(5.3)	(5.8)
Total net periodic postretirement cost	1.7	4.0	3.5
Other changes in plan assets and benefit obligations recognized in other comprehensive loss
Net actuarial (gain) loss	3.4	(15.6)	1.0
Prior service cost	1.7	0.0	0.5
Amortization of net actuarial loss	(2.3)	(4.0)	(4.4)
Amortization of prior service cost	5.1	5.3	5.8
Total change recognized in other comprehensive income	7.9	(14.3)	2.9
Total impact from net periodic postretirement cost and changes in other comprehensive income	9.6	(10.3)	6.4
Pension Plan [Member]
Net periodic postretirement cost
Service cost	1.4	1.7	2.9
Interest cost	12.6	11.5	12.1
Expected return on plan assets	(14.8)	(15.8)	(15.2)
Amortization of net actuarial loss	5.1	5.8	7.6
Amortization of prior service cost	0.7	0.9	1.0
Net periodic postretirement cost	5.0	4.1	8.4
Curtailment or settlement charges	0.0	1.7	3.7
Total net periodic postretirement cost	5.0	5.8	12.1
Other changes in plan assets and benefit obligations recognized in other comprehensive loss
Net actuarial (gain) loss	0.1	16.2	(8.2)
Prior service cost	0.0	(0.1)	1.6
Amortization of net actuarial loss	(5.1)	(7.5)	(7.6)
Amortization of prior service cost	(0.7)	(0.9)	(4.7)
Foreign currency translation	(0.3)	(1.0)	2.9
Total change recognized in other comprehensive income	(6.0)	6.7	(16.0)
Total impact from net periodic postretirement cost and changes in other comprehensive income	(1.0)	12.5	(3.9)
International Plan [Member] | Pension Plan [Member]
Net periodic postretirement cost
Service cost	1.2	1.3	1.4
Interest cost	1.5	1.4	1.6
Expected return on plan assets	0.0	0.0	0.0
Amortization of net actuarial loss	0.8	0.9	1.0
Amortization of prior service cost	0.0	0.0	0.0
Net periodic postretirement cost	3.5	3.6	4.0
Curtailment or settlement charges	0.0	0.0	0.0
Total net periodic postretirement cost	3.5	3.6	4.0
Other changes in plan assets and benefit obligations recognized in other comprehensive loss
Net actuarial (gain) loss	10.3	0.8	(0.3)
Prior service cost	0.0	(0.1)	0.0
Amortization of net actuarial loss	(0.8)	(0.9)	(1.0)
Amortization of prior service cost	0.0	0.0	0.0
Foreign currency translation	(0.3)	(1.0)	2.9
Total change recognized in other comprehensive income	9.2	(1.2)	1.6
Total impact from net periodic postretirement cost and changes in other comprehensive income	12.7	2.4	5.6
United States | Pension Plan [Member]
Net periodic postretirement cost
Service cost	0.2	0.4	1.5
Interest cost	11.1	10.1	10.5
Expected return on plan assets	(14.8)	(15.8)	(15.2)
Amortization of net actuarial loss	4.3	4.9	6.6
Amortization of prior service cost	0.7	0.9	1.0
Net periodic postretirement cost	1.5	0.5	4.4
Curtailment or settlement charges	0.0	1.7	3.7
Total net periodic postretirement cost	1.5	2.2	8.1
Other changes in plan assets and benefit obligations recognized in other comprehensive loss
Net actuarial (gain) loss	(10.2)	15.4	(7.9)
Prior service cost	0.0	0.0	1.6
Amortization of net actuarial loss	(4.3)	(6.6)	(6.6)
Amortization of prior service cost	(0.7)	(0.9)	(4.7)
Foreign currency translation	0.0	0.0	0.0
Total change recognized in other comprehensive income	(15.2)	7.9	(17.6)
Total impact from net periodic postretirement cost and changes in other comprehensive income	$ (13.7)	$ 10.1	$ (9.5)