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Investment Securities (Fair Value Measurement by Level) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Investment securities |  |  |
Percentage of investments recorded at fair value | 91.00% | 88.00% |
Fair value investments | $ 4,050.9 | $ 3,343.6 | $ 3,889.0
Fair value, investment-related liabilities |  | 31.6 |
Debt securities issued by corporations |  |  |
Investment securities |  |  |
Fair value investments | 1,000.0 | 1,171.7 |
Mortgage-backed and asset-backed securities |  |  |
Investment securities |  |  |
Fair value investments | 1,167.0 | 967.9 |
Discontinued Operations |  |  |
Investment securities |  |  |
Investments reclassified to assets held for sale |  |  | 236.3
Level 1 |  |  |
Investment securities |  |  |
Fair value investments | 1,152.2 | 550.6 | 997.2
Level 2 |  |  |
Investment securities |  |  |
Fair value investments | 2,531.4 | 2,372.9 | 2,575.4
Level 2 | Mortgage-backed and asset-backed securities |  |  |
Investment securities |  |  |
Fair value investments | 1,167.0 | 967.9 |
Level 3 Inputs | Mortgage-backed and asset-backed securities |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Level 3 Inputs | Fixed maturity investments |  |  |
Investment securities |  |  |
Fair value investments | 70.0 | 76.4 | 81.8
Level 3 Inputs | Common equity securities |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 39.5 | 45.4
Level 3 Inputs | Other long-term investments |  |  |
Investment securities |  |  |
Fair value investments | 297.3 | 304.2 | 189.2
Fair value measured on a recurring basis |  |  |
Investment securities |  |  |
Fair value investments | 4,262.2 | 3,720.4 |
Fair value measured on a recurring basis | US Government and agency obligations |  |  |
Investment securities |  |  |
Fair value investments | 160.0 | 105.2 |
Fair value measured on a recurring basis | Debt securities issued by corporations |  |  |
Investment securities |  |  |
Fair value investments | 1,000.0 | 1,171.7 |
Fair value measured on a recurring basis | Debt securities issued by corporations | Financials |  |  |
Investment securities |  |  |
Fair value investments | 175.9 | 254.7 |
Fair value measured on a recurring basis | Debt securities issued by corporations | Consumer |  |  |
Investment securities |  |  |
Fair value investments | 253.3 | 259.2 |
Fair value measured on a recurring basis | Debt securities issued by corporations | Industrial |  |  |
Investment securities |  |  |
Fair value investments | 135.6 | 107.3 |
Fair value measured on a recurring basis | Debt securities issued by corporations | Communications |  |  |
Investment securities |  |  |
Fair value investments | 49.2 | 71.5 |
Fair value measured on a recurring basis | Debt securities issued by corporations | Energy |  |  |
Investment securities |  |  |
Fair value investments | 61.5 | 84.1 |
Fair value measured on a recurring basis | Debt securities issued by corporations | Utilities |  |  |
Investment securities |  |  |
Fair value investments | 82.0 | 65.6 |
Fair value measured on a recurring basis | Debt securities issued by corporations | Materials |  |  |
Investment securities |  |  |
Fair value investments | 31.2 | 51.7 |
Fair value measured on a recurring basis | Debt securities issued by corporations | Technology |  |  |
Investment securities |  |  |
Fair value investments | 60.0 | 88.3 |
Fair value measured on a recurring basis | Debt securities issued by corporations | Other |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 7.5 |
Fair value measured on a recurring basis | Mortgage-backed and asset-backed securities |  |  |
Investment securities |  |  |
Fair value investments | 1,167.0 | 967.9 |
Fair value measured on a recurring basis | Preferred stocks |  |  |
Investment securities |  |  |
Fair value investments | 82.7 | 84.2 |
Fair value measured on a recurring basis | Municipal obligations |  |  |
Investment securities |  |  |
Fair value investments | 228.8 | 82.2 |
Fair value measured on a recurring basis | Foreign government, agency and provincial obligations |  |  |
Investment securities |  |  |
Fair value investments | 1.2 | 10.8 |
Fair value measured on a recurring basis | Fixed maturity investments |  |  |
Investment securities |  |  |
Fair value investments | 2,639.7 | 2,422.0 |
Fair value measured on a recurring basis | Short-term investments |  |  |
Investment securities |  |  |
Fair value investments | 211.3 | 376.8 | 310.4
Fair value measured on a recurring basis | Common equity securities | Financials |  |  |
Investment securities |  |  |
Fair value investments | 694.7 | 180.7 |
Fair value measured on a recurring basis | Common equity securities | Consumer |  |  |
Investment securities |  |  |
Fair value investments | 70.0 | 116.0 |
Fair value measured on a recurring basis | Common equity securities | Industrial |  |  |
Investment securities |  |  |
Fair value investments | 26.6 | 57.1 |
Fair value measured on a recurring basis | Common equity securities | Communications |  |  |
Investment securities |  |  |
Fair value investments | 43.7 | 28.5 |
Fair value measured on a recurring basis | Common equity securities | Energy |  |  |
Investment securities |  |  |
Fair value investments |  | 4.9 |
Fair value measured on a recurring basis | Common equity securities | Utilities |  |  |
Investment securities |  |  |
Fair value investments |  | 18.1 |
Fair value measured on a recurring basis | Common equity securities | Materials |  |  |
Investment securities |  |  |
Fair value investments |  | 12.0 |
Fair value measured on a recurring basis | Common equity securities | Technology |  |  |
Investment securities |  |  |
Fair value investments | 27.0 | 44.8 |
Fair value measured on a recurring basis | Common equity securities | Other |  |  |
Investment securities |  |  |
Fair value investments | 74.4 | 75.2 |
Fair value measured on a recurring basis | Common equity securities | Exchange Traded Funds [Member] |  |  |
Investment securities |  |  |
Fair value investments | 141.8 |  |
Fair value measured on a recurring basis | Common equity securities | Common equity securities |  |  |
Investment securities |  |  |
Fair value investments | 1,113.9 | 611.7 |
Fair value measured on a recurring basis | Other long-term investments |  |  |
Investment securities |  |  |
Fair value investments | 297.3 | 309.9 |
Fair value measured on a recurring basis | Level 1 |  |  |
Investment securities |  |  |
Fair value investments | 1,363.5 | 926.9 |
Fair value measured on a recurring basis | Level 1 | US Government and agency obligations |  |  |
Investment securities |  |  |
Fair value investments | 133.4 | 51.2 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations | Financials |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations | Consumer |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations | Industrial |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations | Communications |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations | Energy |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations | Utilities |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations | Materials |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations | Technology |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Debt securities issued by corporations | Other |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Mortgage-backed and asset-backed securities |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Preferred stocks |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Municipal obligations |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 1 | Foreign government, agency and provincial obligations |  |  |
Investment securities |  |  |
Fair value investments | 0.6 | 0.6 |
Fair value measured on a recurring basis | Level 1 | Fixed maturity investments |  |  |
Investment securities |  |  |
Fair value investments | 134.0 | 51.8 |
Fair value measured on a recurring basis | Level 1 | Short-term investments |  |  |
Investment securities |  |  |
Fair value investments | 211.3 | 376.3 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Financials |  |  |
Investment securities |  |  |
Fair value investments | 694.7 | 141.2 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Consumer |  |  |
Investment securities |  |  |
Fair value investments | 70.0 | 115.9 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Industrial |  |  |
Investment securities |  |  |
Fair value investments | 26.6 | 57.1 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Communications |  |  |
Investment securities |  |  |
Fair value investments | 43.7 | 28.5 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Energy |  |  |
Investment securities |  |  |
Fair value investments |  | 4.9 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Utilities |  |  |
Investment securities |  |  |
Fair value investments |  | 18.1 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Materials |  |  |
Investment securities |  |  |
Fair value investments |  | 12.0 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Technology |  |  |
Investment securities |  |  |
Fair value investments | 27.0 | 44.8 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Other |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 1.9 |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Exchange Traded Funds [Member] |  |  |
Investment securities |  |  |
Fair value investments | 120.5 |  |
Fair value measured on a recurring basis | Level 1 | Common equity securities | Common equity securities |  |  |
Investment securities |  |  |
Fair value investments | 1,018.2 | 498.8 |
Fair value measured on a recurring basis | Level 1 | Other long-term investments |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 2 |  |  |
Investment securities |  |  |
Fair value investments | 2,531.4 | 2,373.4 |
Fair value measured on a recurring basis | Level 2 | US Government and agency obligations |  |  |
Investment securities |  |  |
Fair value investments | 26.6 | 54.0 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations |  |  |
Investment securities |  |  |
Fair value investments | 1,000.0 | 1,166.4 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations | Financials |  |  |
Investment securities |  |  |
Fair value investments | 175.9 | 254.7 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations | Consumer |  |  |
Investment securities |  |  |
Fair value investments | 253.3 | 259.2 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations | Industrial |  |  |
Investment securities |  |  |
Fair value investments | 135.6 | 102.0 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations | Communications |  |  |
Investment securities |  |  |
Fair value investments | 49.2 | 71.5 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations | Energy |  |  |
Investment securities |  |  |
Fair value investments | 61.5 | 84.1 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations | Utilities |  |  |
Investment securities |  |  |
Fair value investments | 82.0 | 65.6 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations | Materials |  |  |
Investment securities |  |  |
Fair value investments | 31.2 | 51.7 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations | Technology |  |  |
Investment securities |  |  |
Fair value investments | 60.0 | 88.3 |
Fair value measured on a recurring basis | Level 2 | Debt securities issued by corporations | Other |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 7.5 |
Fair value measured on a recurring basis | Level 2 | Mortgage-backed and asset-backed securities |  |  |
Investment securities |  |  |
Fair value investments | 1,167.0 | 967.9 |
Fair value measured on a recurring basis | Level 2 | Preferred stocks |  |  |
Investment securities |  |  |
Fair value investments | 12.7 | 13.1 |
Fair value measured on a recurring basis | Level 2 | Municipal obligations |  |  |
Investment securities |  |  |
Fair value investments | 228.8 | 82.2 |
Fair value measured on a recurring basis | Level 2 | Foreign government, agency and provincial obligations |  |  |
Investment securities |  |  |
Fair value investments | 0.6 | 10.2 |
Fair value measured on a recurring basis | Level 2 | Fixed maturity investments |  |  |
Investment securities |  |  |
Fair value investments | 2,435.7 | 2,293.8 |
Fair value measured on a recurring basis | Level 2 | Short-term investments |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.5 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Financials |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Consumer |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.1 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Industrial |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Communications |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Energy |  |  |
Investment securities |  |  |
Fair value investments |  | 0.0 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Utilities |  |  |
Investment securities |  |  |
Fair value investments |  | 0.0 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Materials |  |  |
Investment securities |  |  |
Fair value investments |  | 0.0 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Technology |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Other |  |  |
Investment securities |  |  |
Fair value investments | 74.4 | 73.3 |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Exchange Traded Funds [Member] |  |  |
Investment securities |  |  |
Fair value investments | 21.3 |  |
Fair value measured on a recurring basis | Level 2 | Common equity securities | Common equity securities |  |  |
Investment securities |  |  |
Fair value investments | 95.7 | 73.4 |
Fair value measured on a recurring basis | Level 2 | Other long-term investments |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 5.7 |
Fair value measured on a recurring basis | Level 3 Inputs |  |  |
Investment securities |  |  |
Fair value investments | 367.3 | 420.1 |
Fair value measured on a recurring basis | Level 3 Inputs | US Government and agency obligations |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 5.3 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations | Financials |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations | Consumer |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations | Industrial |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 5.3 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations | Communications |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations | Energy |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations | Utilities |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations | Materials |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations | Technology |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Debt securities issued by corporations | Other |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Mortgage-backed and asset-backed securities |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Preferred stocks |  |  |
Investment securities |  |  |
Fair value investments | 70.0 | 71.1 |
Fair value measured on a recurring basis | Level 3 Inputs | Municipal obligations |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Foreign government, agency and provincial obligations |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Fixed maturity investments |  |  |
Investment securities |  |  |
Fair value investments | 70.0 | 76.4 |
Fair value measured on a recurring basis | Level 3 Inputs | Short-term investments |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Financials |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 39.5 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Consumer |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Industrial |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Communications |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Energy |  |  |
Investment securities |  |  |
Fair value investments |  | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Utilities |  |  |
Investment securities |  |  |
Fair value investments |  | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Materials |  |  |
Investment securities |  |  |
Fair value investments |  | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Technology |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Other |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 0.0 |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Exchange Traded Funds [Member] |  |  |
Investment securities |  |  |
Fair value investments | 0.0 |  |
Fair value measured on a recurring basis | Level 3 Inputs | Common equity securities | Common equity securities |  |  |
Investment securities |  |  |
Fair value investments | 0.0 | 39.5 |
Fair value measured on a recurring basis | Level 3 Inputs | Other long-term investments |  |  |
Investment securities |  |  |
Fair value investments | 297.3 | 304.2 |
Carrying value of investment accounted for using the equity method | 3.8 | 5.2 | $ 6.8
Affordable Housing Development Fund [Member] | Other long-term investments |  |  |
Investment securities |  |  |
Fair value investments | $ 14.7 | $ 16.8 |

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- Definition Fair value portion of investments accounted under the equity method. + References Reference 1: 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=35740979&loc=d3e32014-111567 + Details
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- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph a, f, g -Article 7 + Details
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