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Fair Value Measurements - Additional Information (Detail) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 30, 2018 USD ($) Contract | Dec. 31, 2017 USD ($)
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Additional basis point fee need to receive for issuing a CDS on obligation | 0.05% |
Additional basis points fee increase on change of reference obligation spread | 0.15% |
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs | 2.70% | 2.50%
Minimum [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Basis point fee received for issuing a CDS on reference obligation base fee | 0.20% |
Credit spread of reference obligation of a base transaction | 0.80% |
Maximum [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Basis point fee received for issuing a CDS on reference obligation hypothetical fee | 0.25% |
Credit spread of reference obligation of revised transaction | 1.00% |
Successor [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Other investments | $ 394,396 | $ 431,630
Available-for-sale Securities | $ 3,993,015 | $ 5,309,161
Successor [Member] | 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 | 4.00% | 6.00%
PercentageofInvestedPortfiliowhereProjectedCashFlowsConsistSolelyofDeferredAmountsandInterest |  | 13.00%
Successor [Member] | Residential Mortgage-Backed Securities [Member] | Level 3 [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Available-for-sale Securities | $ 0 | $ 736,017
Successor [Member] | Corporate Obligations [Member] | Level 3 [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Available-for-sale Securities | 0 | 0
Successor [Member] | Collateralized Debt Obligations [Member] | Level 3 [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Available-for-sale Securities | $ 0 | $ 0
Successor [Member] | 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 | 2.00% | 15.00%
Successor [Member] | 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 | 94.00% | 79.00%
Variable Interest Entity [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 | 3.40% | 3.10%
Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member] | Corporate Obligations [Member] | Level 3 [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Available-for-sale Securities | $ 2,756,924 | $ 2,914,145
Credit Derivatives [Member] |  |
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items] |  |
Number Of Credit Derivative Contracts On Adversely Classified Credit Listing | Contract | 0 |

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