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Investments - Additional Information (Detail) $ in Millions | 12 Months Ended |
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Dec. 31, 2020 Security | Dec. 31, 2019 USD ($) Security
Investments Debt And Equity Securities [Abstract] |  |
Available-for-sale, investment securities held with maturity dates of more than one year and less than two years | $ |  | $ 24.3
Available-for-sale investment securities contractual maturity dates | less than one year |
Number of available-for-sale investment securities in unrealized loss position | Security | 24 | 20

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- Definition Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922888-210455 + Details
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