Commitments and Contingent Liabilities (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Loss Contingencies [Line Items]
Securities pledged as collateral	$ 353.6	$ 593.7
Possible losses in excess of amounts accrued	45.0
Fixed maturities pledged, included in securities pledged
Loss Contingencies [Line Items]
Securities pledged as collateral	47.2	77.9
Cash collateral, included in Payables
Loss Contingencies [Line Items]
Cash collateral held for securities loan agreement	168.6	110.0
Investment purchase commitment
Loss Contingencies [Line Items]
Off-balance sheet commitment to purchase investments	$ 235.2	$ 536.4

The fair value of available-for-sale securities that serve as collateral for borrowings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 13

-Subparagraph i

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

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The value of the collateral (typically cash) that the entity receives in a financing transaction in exchange for securities lent. This item represents a liability in the financial statements of the lender of the securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(ii))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 30

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 140

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

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-Section 50

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The difference between the maximum amount of estimated loss and the amount recorded as of the balance sheet date.

+ References

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-Publisher FASB

-Name FASB Interpretation (FIN)

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