Investments - Troubled Debt Restructuring (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2014 contract	Dec. 31, 2013 contract
Private placement debt
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructuring contracts	0	0
Commercial mortgage loans
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructuring contracts	0	21
Amount of principal repaid on troubled debt restructurings		4.2
Troubled debt restructurings pre-modification carrying value		91.0
Cross-defaulted, cross-collateralized loans
Financing Receivable, Modifications [Line Items]
Number of troubled debt restructuring contracts		20

Financing Receivable, Modifications, Proceeds From Principal Payments

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 33

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953676-111524

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- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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