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Discontinued Operations (Details) - USD ($) $ in Millions |  | 3 Months Ended | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Apr. 18, 2016 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Jun. 30, 2016 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold |  |  |  |  |  |  |  |  |  |  |  | $ 2,646.2 | $ 24.0 | $ 0.0 |
Payments to Acquire Other Investments |  |  |  |  |  |  |  |  |  |  |  | 39.5 | 78.0 | 114.7 |
Income Tax Expense (Benefit) |  | $ 23.0 | $ 6.7 | $ 6.0 | $ 9.7 | $ 1.0 | $ 1.6 | $ 2.2 | $ (4.6) |  |  | 45.4 | 0.2 | 14.8 |
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  |  | 10.3 | 225.4 | 78.5 |
Recognition of foreign currency translation and other from sale of Sirius Group, net of tax |  |  |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 |
Total investments |  | 5,334.8 |  |  |  | 4,271.1 |  |  |  |  |  | 5,334.8 | 4,271.1 |  |
OCI, Change in foreign currency transaction and translation adjustment, net of tax |  |  |  |  |  |  |  |  |  |  |  | 0.3 | (0.5) | (10.7) |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | 415.1 | 18.2 | (1.6) |
Loss and loss adjustment expense reserves |  | 1,365.6 |  |  |  | 1,389.8 |  |  |  | $ 1,342.2 |  | 1,365.6 | 1,389.8 | 1,342.2 | $ 1,054.3
Net (loss) income from discontinued operations, net of tax |  | (6.8) | 61.9 | 358.6 | $ 1.1 | 19.6 | $ 6.5 | $ (0.5) | $ 71.3 |  |  | (0.3) | 78.7 | 260.6 |
Sirius Group |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold | $ 2,600.0 |  |  | 2,600.0 |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Other Investments | $ 161.8 |  |  | 161.8 |  |  |  |  |  |  |  |  |  |  |
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  |  | 3.7 | 205.0 | 2.7 |
Total investments |  |  |  |  |  | 686.2 |  |  |  |  |  |  | 686.2 |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  | $ 363.2 |  |  |  |  |  |  |  | 363.2 |  |  |
Sirius Group | Symetra |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  |  |  | 200.8 |  |
Total investments |  |  |  |  |  | 528.6 |  |  |  |  |  |  | 528.6 |  |
Sale of Sirius Group [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Recognition of foreign currency translation and other from sale of Sirius Group, net of tax |  |  |  |  |  |  |  |  |  |  | $ 113.3 | 113.3 |  |  |
OCI, Change in foreign currency transaction and translation adjustment, net of tax |  |  |  |  |  |  |  |  |  |  |  | 32.0 | (65.0) | (169.5) |
Tranzact |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold |  | 1.2 | 221.3 |  |  |  |  |  |  |  |  |  |  |  |
Discontinued Operation, Tax Effect of Discontinued Operation |  |  | 30.2 |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  | $ 51.9 |  |  |  |  |  |  |  |  | 51.9 |  |  |
OneBeacon Runoff |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  | $ 36.1 |  |  |  |  |
Esurance [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | 0.0 | 17.9 | 3.2 |
Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  |  | (1.5) | 15.1 | 205.4 |
OCI, Change in foreign currency transaction and translation adjustment, net of tax |  |  |  |  |  |  |  |  |  |  |  |  | (65.0) | (169.5) |
Discontinued Operation, Tax Effect of Discontinued Operation |  |  |  |  |  |  |  |  |  |  |  | (9.5) | 26.4 | 69.4 |
Total income from discontinued operations |  |  |  |  |  |  |  |  |  |  |  | 414.8 | 96.9 | 259.0 |
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | (0.3) | 78.7 | 260.6 |
Discontinued Operations | Sirius Group |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  |  | (1.5) | 15.1 | 205.4 |
Recognition of foreign currency translation and other from sale of Sirius Group, net of tax |  |  |  |  |  |  |  |  |  |  |  | 113.3 |  |  |
OCI, Change in foreign currency transaction and translation adjustment, net of tax |  |  |  |  |  |  |  |  |  |  |  | 32.0 | (65.0) | (169.5) |
Discontinued Operation, Tax Effect of Discontinued Operation |  |  |  |  |  |  |  |  |  |  |  | (3.1) | 27.1 | 70.4 |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | 363.2 |  | 0.0 |
Total income from discontinued operations |  |  |  |  |  |  |  |  |  |  |  | 358.9 | 81.1 | 262.0 |
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | (4.3) | 81.1 | 262.0 |
Discontinued Operations | Tranzact |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Tax Expense (Benefit) |  |  |  |  |  |  |  |  |  |  |  | 21.4 |  |  |
Tax Effect of Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  | 30.2 |  |  |
Discontinued Operation, Tax Effect of Discontinued Operation |  |  |  |  |  |  |  |  |  |  |  | 8.8 |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | 51.9 |  |  |
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | 6.1 | (1.9) | 0.4 |
Discontinued Operations | OneBeacon Runoff |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  |  | 0.3 | $ (18.8) |
Loss and loss adjustment expense reserves |  | $ 18.3 |  |  |  | $ 20.4 |  |  |  |  |  | 18.3 | 20.4 |  |
Percentage of quota share reinsurance agreement |  |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% |
Total income from discontinued operations |  |  |  |  |  |  |  |  |  |  |  |  | (0.5) |  |
Discontinued Operations | Esurance [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | 28.3 | $ 17.9 | $ 3.2 |
Discontinued Operations | Fireman's Fund Insurance Company [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 14.0 |
Discontinued Operations, Held-for-sale [Member] | Star & Shield LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other Expenses |  |  |  |  |  |  |  |  |  |  |  | $ 21.0 |  |  |

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- Definition Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32672-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 3B -URI http://asc.fasb.org/extlink&oid=65878427&loc=SL51721525-107759 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=65878427&loc=SL51721523-107759 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=64827811&loc=d3e1361-107760 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 5B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721673-107760 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=65896914&loc=d3e38679-109324 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 5C -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=64827811&loc=SL51721675-107760 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=65878427&loc=d3e1012-107759 + Details
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- Definition This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (c)-(e) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27357-111563 Reference 2: 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=66902209&loc=d3e3602-108585 Reference 3: 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),9(a)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27405-111563 + Details
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