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Investments in Marketable Securities - Additional Information (Detail) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale, securities in unrealized loss positions, accumulated loss | $ 69,000 | $ 50,000
Allowance for credit losses | $ 0 |
Weighted average contractual maturity | 1 year 8 months 12 days | 1 year 7 months 6 days
Fitch, AA Rating [Member] | Moody's, Aaa Rating [Member] | Standard & Poor's, AA Rating [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Weighted average contractual maturity | 1 year 8 months 12 days |
Fitch, A plus Rating [Member] | Moody's, Aa3 Rating [Member] | Standard & Poor's, A+ Rating [Member] | Weighted Average Credit A Plus Rating [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale, securities number of unrealized loss positions | 27 |
Available-for-sale, securities in unrealized loss positions, accumulated loss | $ 69,000 |
Percentage of amortized cost | 0.30% |

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