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Basis of Preparation and Significant Accounting Policies - Additional Information (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2018 USD ($) period
Property, Plant and Equipment [Line Items] |
Threshold Period of Value Decline in Equity Securities to be considered Other than Temporary Impairment | 12 months
Non-Payment Of Dividends, Number Of Periods | period | 6
Finance Lease, Right-of-Use Asset | $ 76.4
Finance Lease, Liability, Noncurrent | $ 82.0
Computer Equipment | Minimum |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment, Useful Life | 3 years
Computer Equipment | Maximum |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment, Useful Life | 5 years
Furniture and Fixtures |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment, Useful Life | 4 years
Leasehold Improvements |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment, Useful Life | 15 years
Fixed maturities |
Property, Plant and Equipment [Line Items] |
Percentage of Value Decline in Securities to be considered Other than Temporary Impairment | 20.00%
Retained earnings | Accounting Standards Update 2016-02 |
Property, Plant and Equipment [Line Items] |
Cumulative Effect of New Accounting Principle Before Period of Adoption | $ 5.6

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