Pension and Post-Employment Benefits - Reconciliation of Fair Value of Plan Assets Measured Using Significant Unobservable Inputs (Detail) - United Kingdom Plan [Member] - Significant Unobservable Inputs (Level 3) [Member] - Other Assets [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 162.8	$ 152.9
Realized/unrealized gains/(losses):
Relating to assets still held at the reporting date	(4.8)	2.8
Relating to assets sold during the period	0.0	0.0
Purchases, issuances and settlements	(6.7)	(7.4)
Exchange effect	(8.8)	14.5
Ending balance	$ 142.5	$ 162.8

Pension and Post-Employment Benefits - Reconciliation of Fair Value of Plan Assets Measured Using Significant Unobservable Inputs (Detail) - United Kingdom Plan [Member] - Significant Unobservable Inputs (Level 3) [Member] - Other Assets [Member] - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2018

Dec. 31, 2017

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]

Beginning balance

$ 162.8

$ 152.9

Realized/unrealized gains/(losses):

Relating to assets still held at the reporting date

(4.8)

2.8

Relating to assets sold during the period