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Available-for-Sale Investments - Additional Information (Detail) $ in Millions | Dec. 31, 2019 USD ($) Investment Security | Dec. 31, 2018 USD ($)
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Investments Debt And Equity Securities [Abstract] |  |
Number of investments in unrealized loss position | 9 |
Number of investments in unrealized loss position, more than twelve months | 0 |
Aggregate fair value of securities in unrealized loss position | $ | $ 24.8 | $ 96.5
Number of securities with other than temporary impairment | Security | 0 |

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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 continuous unrealized loss position for 12 months or longer, without an allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922888-210455 + Details
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