Pension Plans - Reconciliation of Fair Value of Plan Assets Measured at Net Asset Value (Detail) - United Kingdom Plan [Member] - Non-financial Assets and Liabilities (Level 3 Measurement) [Member] - Other Assets [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 44.1	$ 38.3
Realized/unrealized gains/(losses):
Relating to assets still held at the reporting date	4.7	7.3
Relating to assets sold during the period	0.0	0.0
Purchases, issuances and settlements	6.5	0.7
Exchange effect	(7.7)	(2.2)
Ending balance	$ 47.6	$ 44.1

Pension Plans - Reconciliation of Fair Value of Plan Assets Measured at Net Asset Value (Detail) - United Kingdom Plan [Member] - Non-financial Assets and Liabilities (Level 3 Measurement) [Member] - Other Assets [Member] - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2015

Dec. 31, 2014

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

Beginning balance

$ 44.1

$ 38.3

Realized/unrealized gains/(losses):

Relating to assets still held at the reporting date

4.7

7.3

Relating to assets sold during the period