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Cash and Investments in Marketable Securities - Additional Information (Detail) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2021 | Dec. 31, 2020
Cash and Investments in Marketable Securities [Line Items] |  |
Maximum maturity term for debt securities investment | 2 years |
Weighted average maturity term for debt securities investment (or less) | 1 year |
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax |  | $ 1.1
Debt securities, available-for-sale accumulated gross unrealized loss, before tax |  | $ 0.2
Minimum |  |
Cash and Investments in Marketable Securities [Line Items] |  |
Long term investment maturity period | 1 year | 1 year
Maximum |  |
Cash and Investments in Marketable Securities [Line Items] |  |
Long term investment maturity period | 2 years | 2 years

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- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563 + Details
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