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Commitments and Contingencies - Additional Information (Detail) |  | 6 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2020 Officer | Jun. 30, 2021 USD ($) | Mar. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
Contingencies And Commitments [Line Items] |  |  |  |
Commitments related to performance bonds |  | $ 21,200,000 |  | $ 15,200,000
Commitments related to performance bonds expiration month and year |  | 2024-08 |  |
Letter of credit secured by pledge of a portion of fixed income securities |  | $ 18,200,000 |  |
Commitments towards private equity funds |  | 4,900,000 |  |
Investment Commitments [Member] |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |
Aggregate investment committed in private equity funds |  | 5,000,000.0 |  |
Long-term Investments [Member] |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |
Letter of credit secured by pledge of a portion of fixed income securities |  | 18,200,000 |  |
Minimum [Member] |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |
Collateral value required to be maintained |  |  | $ 15,000,000.0 |
Maximum [Member] | Restricted Cash [Member] |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |
Letter of credit secured by pledge of a portion of fixed income securities |  | $ 100,000 |  |
Current Executive Officers [Member] |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |
Number of officers | Officer | 2 |  |  |
Former Executive Officers [Member] |  |  |  |
Contingencies And Commitments [Line Items] |  |  |  |
Number of officers | Officer | 1 |  |  |

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- Definition Commitments related to performance bonds. + References No definition available. + Details
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- Definition Commitments related to performance bonds expiration month and year. + References No definition available. + Details
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- Definition Letter of credit secured by pledge of a portion of fixed income securities. + References No definition available. + Details
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- Definition Amount of assets pledged to secure a debt instrument. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 50 -Paragraph 3 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823 + Details
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