Derivatives and Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Derivative [Line Items]
Cost-method Investments, Realized Losses			$ 21.2
Asset impairment	$ 0.0	$ 18.2
Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount	19.5		17.0
Currency Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	816.6		770.0
Gain (Loss) on Derivative Used in Net Investment Hedge, after Tax	$ (4.0)		$ (1.8)

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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For investments in debt and equity securities accounted for at cost, the excess of the carrying amount over net sale proceeds of investments disposed of during the period and any losses recognized thereon for impairments of other than a temporary nature.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Nominal or face amount used to calculate payment on derivative.

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Amount, after tax, of reclassification from accumulated other comprehensive income (AOCI) of gain (loss) from increase (decrease) in fair value of net investment hedge.

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