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Investments in Unconsolidated Affiliates (Symetra) (Details) (Symetra, USD $) In Millions, except Per Share data, unless otherwise specified | 3 Months Ended | 12 Months Ended | 3 Months Ended
--- | --- | --- | ---
Mar. 31, 2013 | Dec. 31, 2011 | Mar. 31, 2013 Common Stock | Mar. 31, 2012 Common Stock
Investments in unconsolidated affiliates |  |  |  |
Shares of Symetra Financial Corporation owned (in shares) | 17.4 |  |  |
Investments in unconsolidated affiliates on conversion of warrants | 9.5 |  |  |
Fair value of investment |  | $ 261.0 |  |
Estimated fair value of investment per share |  | $ 15 |  |
After-tax equity in losses of unconsolidated affiliates |  | 45.9 |  |
Equity in net unrealized losses increase relating to amortization of common share impairment |  | 136.6 | 2.7 | 3.2
Ownership interest (as a percent) | 15.00% |  |  |
Difference between fair value and carrying amount |  | 195.8 |  |
Term of amortization (in years) | 30 years |  |  |
After tax amortization through equity in earnings | 0.7 |  |  |
After tax amortization through equity in net unrealized losses | 2.5 |  |  |
Pre-tax unamortized basis difference | $ 175.7 |  |  |
Risk free interest rate (as a percent) | 0.17% |  |  |
Volatility rate (as a percent) | 29.10% |  |  |
Expected life (in years) | 1 year 3 months 29 days |  |  |
Class of warrant or right fair value assumptions per strike price | $ 11.49 |  |  |
Share price | $ 13.41 |  |  |

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- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investments accounted for under the equity method of accounting as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 6 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 -Topic 323 -SubTopic 10 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6903542&loc=d3e32014-111567 + Details
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