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Investment Securities Investment Securities (Net Unrealized Investment Gains (Losses)) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Investment securities |  |  |
Trading Securities, Change in Unrealized Holding Gain (Loss) | $ 38.9 | $ 98.7 | $ (63.6)
Foreign Currency Transaction Gain (Loss), Unrealized | 18.3 | (48.6) | 69.4
Net unrealized investment gains, pre-tax | 57.2 | 50.1 | 5.8
Trading Securities, Tax on Unrealized Holding Gain (Loss) on Investments | 8.2 | (17.9) | 24.0
Trading Securities, Unrealized Foreign Currency Transaction Gain (Loss) Tax | (5.6) | 12.7 | (17.9)
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Tax | 2.6 | (5.2) | 6.1
Trading Securities Unrealized Holding Gain (Loss) on Investments after Tax | 47.1 | 80.8 | (39.6)
Trading Securities, Unrealized Foreign Currency Gain (Loss) Net of Tax | 12.7 | (35.9) | 51.5
Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Net of Tax | 59.8 | 44.9 | 11.9
Fixed maturity investments |  |  |
Investment securities |  |  |
Trading Securities, Change in Unrealized Holding Gain (Loss) | (93.9) | 18.5 | 7.6
Foreign Currency Transaction Gain (Loss), Unrealized | 15.3 | (45.9) | 68.9
Net unrealized investment gains, pre-tax | (78.6) | (27.4) | 76.5
Short-term investments |  |  |
Investment securities |  |  |
Trading Securities, Change in Unrealized Holding Gain (Loss) | 0.1 | 0 | 0
Foreign Currency Transaction Gain (Loss), Unrealized | 0 | 0.1 | (1.1)
Net unrealized investment gains, pre-tax | 0.1 | 0.1 | (1.1)
Common equity securities |  |  |
Investment securities |  |  |
Trading Securities, Change in Unrealized Holding Gain (Loss) | 119.2 | 65.9 | (40.6)
Foreign Currency Transaction Gain (Loss), Unrealized | (0.4) | (0.1) | (1.8)
Net unrealized investment gains, pre-tax | 118.8 | 65.8 | (42.4)
Convertible fixed maturity investments |  |  |
Investment securities |  |  |
Trading Securities, Change in Unrealized Holding Gain (Loss) | 3.2 | 1.1 | (11.5)
Foreign Currency Transaction Gain (Loss), Unrealized | 0 | 0 | 0
Net unrealized investment gains, pre-tax | 3.2 | 1.1 | (11.5)
Other long-term investments |  |  |
Investment securities |  |  |
Trading Securities, Change in Unrealized Holding Gain (Loss) | 10.3 | 13.2 | (19.1)
Foreign Currency Transaction Gain (Loss), Unrealized | 3.4 | (2.7) | 3.4
Net unrealized investment gains, pre-tax | 13.7 | 10.5 | (15.7)
Forward contracts |  |  |
Investment securities |  |  |
Trading Securities, Change in Unrealized Holding Gain (Loss) | 0 |  |
Foreign Currency Transaction Gain (Loss), Unrealized | 0 |  |
Net unrealized investment gains, pre-tax | $ 0 |  |

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- Definition Amount before tax of foreign currency transaction unrealized gain (loss) recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450189&loc=d3e30690-110894 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6450189&loc=d3e30700-110894 + Details
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- Definition Amount of unrealized holding gain (loss) recognized in the income statement for investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(c)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560 + Details
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- Definition The aggregate of the change in unrealized holding gain (loss) and foreign currency gain (loss) included in earnings during the reporting period. + References No definition available. + Details
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- Definition The after-tax aggregate of the change in unrealized holding gain (loss) and foreign currency gain (loss) included in earnings during the reporting period. + References No definition available. + Details
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- Definition Net Unrealized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Tax + References No definition available. + Details
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- Definition The after-tax gain (loss) attributable to the foreign currency transaction gain (loss) on trading securities held at each balance sheet date, that was included in earnings in the period. + References No definition available. + Details
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- Definition The tax expense (benefit) attributable to the foreign currency transaction gain (loss) on trading securities held at each balance sheet date, that was included in earnings in the period. + References No definition available. + Details
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