Financial Instruments and Fair Value Measurements - Foreign Currency Contracts Activity (Parenthetical) (Detail) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($) Contracts	Dec. 31, 2016 USD ($) Contracts	Dec. 31, 2015 USD ($) Contracts
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Number of option contracts exercised \| Contracts	44	49	32
Gains (losses) from option contracts exercised \| $	$ 12.6	$ 3.0	$ 14.6

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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Balance Type:	credit
Period Type:	duration