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Investments - Additional Information (Detail) - USD ($) | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2019 | Jun. 30, 2020 | Jan. 01, 2020 | Dec. 31, 2019
Schedule of Investments [Line Items] |  |  |  |
Purchase an available-for-sale debt securities with credit deterioration |  | $ 0 |  |
Transfer from investments | $ 3,400,000 |  |  |
Carrying value |  |  |  | $ 3,400,000
Note receivable, noncurrent |  | 900,000 | $ 900,000 |
Asset impairments |  | 65,000 |  |
Carrying value of investment |  | 1,800,000 |  |
Net Investment Gain (Loss) [Member] |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Asset impairments |  | 1,600,000 |  |
Other Receivables [Member] |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Note receivable, current | $ 4,300,000 | 4,300,000 |  | 4,300,000
Asset impairments |  | 0 |  |
Long-term Investments [Member] |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Note receivable, noncurrent |  | $ 900,000 |  | $ 900,000
Investment [Member] | Issuer Concentration [Member] | Market Value of Total Investment Portfolio [Member] |  |  |  |
Schedule of Investments [Line Items] |  |  |  |
Investment concentration risk percentage |  | 5.00% |  |

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