Derivatives and Hedging Activity - Summary of Notional and Fair Values of Derivative Instruments (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative assets - current	$ 13.6	$ 7.7
Derivative assets - non current	0.3	2.7
Derivative liabilities - current	4.7	1.6
Derivative liabilities - non current	4.4	1.3
Foreign Exchange Contracts [Member] \| Call Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	105.4	141.0
Foreign Exchange Contracts [Member] \| Put Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	105.4	141.0
Foreign Exchange Contracts [Member] \| Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	19.2	13.3
Foreign Exchange Contracts [Member] \| Forward Contracts [Member] \| Call Options [Member]
Derivatives, Fair Value [Line Items]
Foreign exchange derivative contracts	$ 80.3	$ 31.0

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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