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Pension and Post-employment Benefits - Defined Benefit Pension Plan (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
United Kingdom Plan [Member]
Plan assumptions at December 31, (%):
Discount rate	2.56%	2.48%	3.69%
Inflation rate	2.20%	2.25%	2.15%
Rate of return on plan assets	2.75%	3.20%	4.20%
Plan asset allocation by category (%):
Total plan asset allocation by category	100.00%	100.00%	100.00%
United Kingdom Plan [Member] | Equity Securities [Member]
Plan asset allocation by category (%):
Total plan asset allocation by category	38.00%	25.00%	34.00%
United Kingdom Plan [Member] | Debt Securities [Member]
Plan asset allocation by category (%):
Total plan asset allocation by category	53.00%	66.00%	62.00%
United Kingdom Plan [Member] | Cash [Member]
Plan asset allocation by category (%):
Total plan asset allocation by category	9.00%	9.00%	4.00%
United Kingdom [Member] | Foreign Pension Plan [Member]
Plan net pension (credit)/charge:
Service cost	$ 0.9	$ 1.0	$ 1.5
Interest cost on PBO	15.2	20.7	27.7
Expected return on plan assets	(24.5)	(29.9)	(33.4)
Amortization of prior service credit	(1.0)	(1.1)	(1.2)
Amortization of actuarial net losses	5.0	2.6	5.2
Net pension charge	$ (4.4)	$ (6.7)	$ (0.2)

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Defined benefit plan assumptions used calculating net periodic benefit cost inflation rate.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan.

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Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

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Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

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Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of net periodic benefit cost (credit) for defined benefit plan.

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Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held.

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