Investments (Investments Pledged as Collateral) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Assets Held by Insurance Regulators	$ 25.7
Securities pledged as collateral for reinsurance obligations	164.9
U.S. Government and Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held by Insurance Regulators	22.6
Securities pledged as collateral for reinsurance obligations	25.6
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0.0
Assets Held by Insurance Regulators	3.1
Securities pledged as collateral for reinsurance obligations	3.1
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held by Insurance Regulators	0.0
Securities pledged as collateral for reinsurance obligations	20.3
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held by Insurance Regulators	0.0
Securities pledged as collateral for reinsurance obligations	115.9
Federal Home Loan Bank of New York [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	73.7
Federal Home Loan Bank of New York [Member] \| U.S. Government and Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	0.0
Federal Home Loan Bank of New York [Member] \| Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	14.1
Federal Home Loan Bank of New York [Member] \| Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	59.6
Federal Home Loan Bank of Indianapolis [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	65.5
Federal Home Loan Bank of Indianapolis [Member] \| U.S. Government and Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	3.0
Federal Home Loan Bank of Indianapolis [Member] \| Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	6.2
Federal Home Loan Bank of Indianapolis [Member] \| Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	$ 56.3

Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 320
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75027294&loc=d3e22002-158495

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Amount of the collateral pledged in support of federal home loan bank advances outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

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Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Paragraph 1
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