Investments - Schedule of Realized and Unrealized Gains and Losses on Investments (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Investments Debt And Equity Securities [Abstract]
Unrealized (losses) gains on equity securities held as of the end of the period	$ (11.1)	$ 7.3
Realized gains (losses) for equity securities sold during the period	1.4	(0.2)
Total (losses) gains recognized in other (expense) income, net	$ (9.7)	$ 7.1

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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