Basis of Preparation and Significant Accounting Policies - Additional Information (Details) $ in Millions	12 Months Ended
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

Cumulative Effect of New Accounting Principle Before Period of Adoption

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- Definition

Non-Payment Of Dividends, Number Of Periods

+ References

No definition available.

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- Definition

Present value of lessee's discounted obligation for lease payments from finance lease, classified as noncurrent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

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- Definition

Amount of lessee's right to use underlying asset under finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

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- Definition

Threshold percentage by which investments in equity securities have declined in value to be considered other than temporary impairment (OTTI).

+ References

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Threshold period for investment in equity securities in a continuous decline in value to be considered other than temporary impairment (OTTI), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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