Other Post-Employment Benefits and Other Employee Benefit Plans - Reconciliation of Benefit Obligations, Plan Assets and Funded Status for Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in benefit obligations:
Benefit obligation at beginning of period	$ 978.9	$ 963.0
Service cost	7.0	10.6	$ 11.4
Interest cost	22.9	26.1	30.4
Actuarial loss (gain)	27.8	81.5
Benefits paid, net	(35.5)	(39.9)
Loss due to exchange rate movements	57.6	(56.4)
Benefit obligation at end of period	906.9	978.9	963.0
Change in plan assets:
Fair value of plan assets at beginning of period	771.8	760.3
Employer contribution	28.1	17.9
Benefits paid, net	(35.5)	(39.9)
Fair value of plan assets at end of period	776.2	771.8	760.3
Net amount recognized:
Underfunded status	(130.7)	(207.1)
Accumulated benefit obligation at end of year	893.7	933.7
Net amount recognized in consolidated balance sheets consists of:
Current liability	(2.4)	(2.5)
Non-current liability	(169.4)	(182.0)
Net amount recognized	(132.7)	(166.7)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss	146.1	205.0
Prior service credit	0.7	(1.2)
Total	146.8	203.8
Other Post-Employment Benefits and Other Employee Benefit Plans
Change in benefit obligations:
Benefit obligation at beginning of period	54.0	64.4
Service cost	0.1	0.2	0.8
Interest cost	1.6	1.9	2.9
Actuarial loss (gain)	1.0	(6.3)
Benefits paid, net	(4.3)	(4.3)
Settlement/curtailment	(1.2)	0.0
Loss due to exchange rate movements	0.1	0.0
Plan amendments	0.0	(1.9)
Benefit obligation at end of period	51.3	54.0	64.4
Change in plan assets:
Fair value of plan assets at beginning of period	0.0	0.0
Employer contribution	4.3	4.3
Benefits paid, net	(4.3)	(4.3)
Fair value of plan assets at end of period	0.0	0.0	$ 0.0
Net amount recognized:
Underfunded status	(51.3)	(54.0)
Accumulated benefit obligation at end of year	51.3	54.0
Net amount recognized in consolidated balance sheets consists of:
Current liability	(5.2)	(3.0)
Non-current liability	(46.1)	(51.0)
Net amount recognized	(51.3)	(54.0)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss	2.0	2.0
Prior service credit	(3.1)	(17.9)
Total	$ (1.1)	$ (15.9)