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Marketable Securities - Narrative (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract] |  |  |
Realized gain (loss) on sales of marketable securities | $ 0 | $ 28,500,000 | $ 0

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- Definition Amount of realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI). + References No definition available. + Details
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