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Fair Value of Financial Instruments Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |  |
Gain (Loss) on Embedded Derivative | $ (1.7) | $ 8.6 |
Fair Value of Financial Instruments Additional Information [Abstract] |  |  |
Ceded Policy Loans | $ 3,306.8 |  | $ 3,307.5
Fair Value Inputs Other Than Level 1 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |  |
Percentage of Total Fair Value of Fixed Maturities Securities | 79.30% |  |
Fair Value, Inputs, Level 1 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |  |
Percentage of Total Fair Value of Fixed Maturities Securities | 20.70% |  |
Fair Value, Inputs, Level 2 | Pricing Service |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |  |
Percentage of Total Fair Value of Fixed Maturities Securities | 66.00% |  |
Fair Value, Inputs, Level 2 | Other Observable Market Data |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |  |
Percentage of Total Fair Value of Fixed Maturities Securities | 2.40% |  |
Fair Value Inputs Level 2 Or Level 3 |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis |  |  |
Percentage of Total Fair Value of Fixed Maturities Securities | 10.90% |  |

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- Definition Loans ceded to reinsurers. These loans use insurance policy funds such as cash surrender values as collateral. + References No definition available. + Details
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- Definition Net Increase or Decrease in the fair value of the embedded derivative or group of embedded derivatives included in earnings in the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 + Details
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