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Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Other Investments | $ 595,000 | $ 478,000
Credit valuation adjustment included in fair value of credit derivative liabilities | 32 | 19
Fair value of derivative liabilities | 113,000 |
Derivative liabilities | $ 114,000 | $ 90,000
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs | 2.20% | 2.40%
Fixed Income Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Percentage of investment portfolio valued using dealer quotes | 2.00% | 4.00%
Asset-backed Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Coupon rate | 5.97% | 5.97%
Minimum [Member] | Fixed Income Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Percentage of investment portfolio valued using internal valuation models | 3.00% | 2.00%
Maximum [Member] | Fixed Income Securities [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Percentage of investment portfolio valued using external pricing services | 95.00% | 94.00%
Variable Interest Entity, Primary Beneficiary [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs | 2.40% | 2.70%
Real Estate [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Other Investments | $ 16,000 | $ 16,000
Hedge Funds, Multi-strategy [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Other Investments | 196,000 | 65,000
Interest Rate Contract [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Other Investments | 78,000 | 176,000
Illiquid Investments [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Other Investments | $ 65,000 | 51,000
Other Credit Derivatives [Member] | Level 3 [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Derivative liabilities |  | $ 0

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