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Cash, Cash Equivalents, Restricted Cash and Marketable Securities - Additional Information (Detail) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Investments Debt And Equity Securities [Abstract] |  |  |  |
Realized gains on investments | $ 100,000 | $ 0 | $ 100,000 | $ 0
Realized loss on investments | $ 0 | $ 0 | $ 0 | $ 0

X
- Definition This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
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- Definition This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
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