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Investment Securities (Cost and Amortized Cost Maturity Schedule) (Details) (USD $) In Millions, unless otherwise specified |  | 12 Months Ended |  |  |  |  | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2012 | Dec. 31, 2012 Including Short Term Fixed | Dec. 31, 2012 Fixed Maturities and Convertible Fixed Maturities Excluding A B S M B S and Preferred Stock | Dec. 31, 2012 Mortgage-backed and asset-backed securities | Dec. 31, 2011 Mortgage-backed and asset-backed securities | Dec. 31, 2012 Preferred stocks | Dec. 31, 2011 Preferred stocks | Dec. 31, 2012 Excluding Short Term Investments
Schedule of Trading Securities and Other Trading Assets [Line Items] |  |  |  |  |  |  |  |
Duration of Fixed Maturities including short-term investments in years |  | 2 years 4 months 24 days |  |  |  |  |  | 2 years 8 months 12 days
Trading Securities by Maturity Cost or Amortized Cost |  |  |  |  |  |  |  |
Due in one year or less |  |  | $ 395.9 |  |  |  |  |
Due after one year through five years |  |  | 2,297.8 |  |  |  |  |
Due after five years through ten years |  |  | 648.9 |  |  |  |  |
Due after ten years |  |  | 72.8 |  |  |  |  |
Trading Securities, Maturities without Single Maturity Date, Amortized Cost |  |  |  | 2,081.0 |  | 79.9 |  |
Cost or amortized cost | 5,576.3 |  |  | 2,081.0 | 3,190.5 | 79.9 | 82.3 |
Trading Securities by Maturity, Fair Value |  |  |  |  |  |  |  |
Due in one year or less |  |  | 396.7 |  |  |  |  |
Due after one year through five years |  |  | 2,336.7 |  |  |  |  |
Due after five years through ten years |  |  | 671.6 |  |  |  |  |
Due after ten years |  |  | 74.7 |  |  |  |  |
Trading Securities, Maturities without Single Maturity Date, Carrying Value |  |  |  | 2,095.6 |  | 86.4 |  |
Trading Securities | $ 5,661.7 |  |  |  |  |  |  |

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- Definition The total of financial instruments that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for debt and equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 -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 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph a -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 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 29 -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 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Implementation Guide (Q and A) -Number FAS115 -Paragraph 35 -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. + Details
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- Definition This item represents the cost of trading securities, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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- Definition This item represents securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature after five years and through ten years from the balance sheet date classified as trading. + References No definition available. + Details
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- Definition This item represents securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature after ten years from the balance sheet classified as trading. + References No definition available. + Details
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- Definition This item represents securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature within one year of the balance sheet date classified as trading. + References No definition available. + Details
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