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Investment Securities (Net Realized Investment Gains (Losses)) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2014 | Mar. 31, 2013
Investment securities |  |
Trading Securities, Realized Gain (Loss) | $ 25.3 | $ 51.2
Trading securities, tax on realized holding gain (loss) on investments | (4.6) | (11.8)
Trading securities realized holding gain (loss) on investments after tax | 20.7 | 39.4
Foreign Currency Transaction Gain (Loss), Realized | (3.6) | (14.7)
Trading securities, realized foreign currency transaction gain (loss) t | 0.9 | 3.3
Trading securities, realized foreign currency gain (loss) net of tax | (2.7) | (11.4)
Trading Securities, Realized Gain (Loss), Total | 21.7 | 36.5
Tax on Net Realized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities | (3.7) | (8.5)
Net Realized Gain (Loss) and Foreign Currency Gain (Loss) on Trading Securities Net of Tax | 18.0 | 28.0
Fixed maturity investments. |  |
Investment securities |  |
Trading Securities, Realized Gain (Loss) | 4.4 | 22.6
Foreign Currency Transaction Gain (Loss), Realized | (3.5) | (14.6)
Trading Securities, Realized Gain (Loss), Total | 0.9 | 8.0
Short-term investments |  |
Investment securities |  |
Trading Securities, Realized Gain (Loss) | 0 | 0
Foreign Currency Transaction Gain (Loss), Realized | 0 | 0.1
Trading Securities, Realized Gain (Loss), Total | 0 | 0.1
Common equity securities |  |
Investment securities |  |
Trading Securities, Realized Gain (Loss) | 18.9 | 22.6
Foreign Currency Transaction Gain (Loss), Realized | (0.1) | (0.2)
Trading Securities, Realized Gain (Loss), Total | 18.8 | 22.4
Convertible fixed maturity investments |  |
Investment securities |  |
Trading Securities, Realized Gain (Loss) | 2.4 | 2.7
Foreign Currency Transaction Gain (Loss), Realized | 0 | 0
Trading Securities, Realized Gain (Loss), Total | 2.4 | 2.7
Other long-term investments |  |
Investment securities |  |
Trading Securities, Realized Gain (Loss) | (0.3) | 2.9
Foreign Currency Transaction Gain (Loss), Realized | 0 | 0
Trading Securities, Realized Gain (Loss), Total | (0.3) | 2.9
Forward Contracts |  |
Investment securities |  |
Trading Securities, Realized Gain (Loss) | (0.1) | 0.4
Foreign Currency Transaction Gain (Loss), Realized | 0 | 0
Trading Securities, Realized Gain (Loss), Total | $ (0.1) | $ 0.4

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- Definition Amount before tax of foreign currency transaction realized gain (loss) recognized in the income statement. + References Reference 1: 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 2: 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 3: 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 This item represents the gain (loss) realized during the period from the sale of trading securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Subparagraph c -Article 5 Reference 2: 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 3: 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 4: 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 + Details
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