Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Fair Value Disclosures (Narrative) (Details) - USD ($)	12 Months Ended
Fair Value Disclosures (Narrative) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Level 1 and Level 2 financial assets	$ 0	$ 0
Remaining goodwill	0	0	$ 0
Fixed Maturity and Equity Securities \| IDC \| Level 3 \| Market Approach Valuation Technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	3,000,000.0	5,700,000
Priced Internally \| Fixed Maturity and Equity Securities \| Level 3 \| Market Approach Valuation Technique
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 133,600,000	102,300,000
Corporate & Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible asset impairment charge		$ 16,700,000