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Investments - Additional Information (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 USD ($) security | Dec. 31, 2018 USD ($) security | Sep. 30, 2020 security
Investments |  |  |
Number of debt securities held | 9 | 7 | 7
Pre-tax net realized capital gains or losses | $ | $ 0.0 | $ 0.0 |
Number of debt securities held, unrealized loss position for 12 months or more | 4 | 6 | 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=121582814&loc=SL82922888-210455 + Details
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- Definition Amount of realized gain (loss) on investment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.3(a)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details
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