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Fair Value Measurements (Narrative) (Detail) $ in Millions | 9 Months Ended
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Sep. 30, 2021 USD ($)
Level 2 | Non Marketable Equity Securities |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
Net unrealized gains (losses) on equity securities | $ 165.1

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- Definition Amount of gain from upward price adjustment on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123583765&loc=SL75117539-209714 + Details
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