Investments - Gross Unrealized Gains and (Losses) Aggregated by Investment Category (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	$ 61.5	$ 109.7
Investments, Gross Unrealized Gains	0.1
Investments, Gross Unrealized (Losses)	(0.2)	(0.3)
Investments, Estimated Fair Value	61.4	109.4
Time Deposits and Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	10.4	13.1
Investments, Estimated Fair Value	10.4	13.1
Bankers' Acceptance Drafts [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	2.4	4.0
Investments, Estimated Fair Value	2.4	4.0
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	26.4	61.5
Investments, Gross Unrealized (Losses)	(0.2)	(0.3)
Investments, Estimated Fair Value	26.2	61.2
U.S. Treasury Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	10.0	5.0
Investments, Estimated Fair Value	10.0	5.0
U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	12.3	26.1
Investments, Gross Unrealized Gains	0.1
Investments, Estimated Fair Value	12.4	26.1
Group Insurance Contracts [Member] \| Long Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Cost	5.4	5.2
Investments, Gross Unrealized Gains	0.6	0.6
Investments, Estimated Fair Value	$ 6.0	$ 5.8

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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- Definition

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.

+ References

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