Financial Instruments and Fair Value Measurements - Foreign Currency Contracts Activity (Parenthetical) (Detail) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($) Derivative Contracts	Mar. 31, 2017 USD ($) Contracts
Derivative [Line Items]
Number of forward and option contracts exercised \| Contracts	15	11
Gains (losses) from forward and option contracts exercised \| $	$ (6.8)	$ 5.3
Net Investment Hedges [Member] \| CAD
Derivative [Line Items]
Number of investment hedges settled \| Derivative	2

For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14172-108612

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration