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Discontinued Operations (Net Income (Loss) from Discontinued Operations) (Details) - USD ($) $ in Millions |  |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Sep. 28, 2017 | Oct. 05, 2016 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Revenues |  |  |  |  |  |  |  |  |  |  |  |  |
Earned insurance premiums |  |  |  |  |  |  |  |  |  |  | $ 10.4 | $ 13.4 | $ 12.0
Net investment income |  |  |  |  |  |  |  |  |  |  | 56.0 | 32.1 | 10.9
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  | 133.3 | (27.4) | 260.5
Other revenues |  |  |  |  |  |  |  |  |  |  | 7.1 | 21.3 | 49.2
Revenues |  |  |  | $ 87.5 | $ 83.5 | $ 88.8 | $ (5.5) | $ 56.8 | $ 48.4 | $ 58.0 | 373.8 | 157.7 | 440.0
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  |  |  | 1.1 | 8.0 | 8.2
Insurance acquisition expenses |  |  |  |  |  |  |  |  |  |  | 4.1 | 5.6 | 6.3
Other underwriting expenses |  |  |  |  |  |  |  |  |  |  | 0.4 | 0.4 | 0.4
General and administrative expenses |  |  |  |  |  |  |  |  |  |  | 218.7 | 186.0 | 200.7
Interest expense |  |  |  |  |  |  |  |  |  |  | 2.3 | 3.0 | 1.6
Total expenses |  |  |  | 79.1 | 85.7 | 92.4 | 69.0 | 70.6 | 74.1 | 91.3 | 366.0 | 305.0 | 310.8
Net (loss) income from discontinued operations, net of tax |  |  | $ 4.3 | $ 539.1 | $ 2.8 | $ 31.3 | $ 8.0 | 84.4 | $ 383.6 | $ 47.4 | 20.5 | 108.3 | 116.9
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | 557.0 | 415.1 | 18.2
Total income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | 577.5 | 523.4 | 135.1
Comprehensive income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | 630.7 | 547.4 | 187.4
Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Total income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | 577.5 | 523.4 | 135.1
OneBeacon |  |  |  |  |  |  |  |  |  |  |  |  |
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | 20.5 | 108.6 | 38.2
Gain (loss) from sale of other discontinued operations, net of tax | $ 554.6 |  |  |  |  |  |  |  |  |  | 554.5 | 0.0 | 0.0
OneBeacon | Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |  |  |
Earned insurance premiums |  |  |  |  |  |  |  |  |  |  | 807.6 | 1,100.6 | 1,176.2
Net investment income |  |  |  |  |  |  |  |  |  |  | 39.7 | 50.6 | 45.9
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  | 38.8 | 37.7 | (35.1)
Other revenues |  |  |  |  |  |  |  |  |  |  | 7.7 | 5.5 | (0.6)
Revenues |  |  |  |  |  |  |  |  |  |  | 893.8 | 1,194.4 | 1,186.4
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  |  |  | 546.0 | 656.0 | 700.7
Insurance acquisition expenses |  |  |  |  |  |  |  |  |  |  | 145.6 | 206.0 | 213.8
Other underwriting expenses |  |  |  |  |  |  |  |  |  |  | 156.2 | 209.0 | 218.2
General and administrative expenses |  |  |  |  |  |  |  |  |  |  | 21.2 | 14.2 | 13.0
Interest expense |  |  |  |  |  |  |  |  |  |  | 10.0 | 13.1 | 15.4
Total expenses |  |  |  |  |  |  |  |  |  |  | 879.0 | 1,098.3 | 1,161.1
Pre-tax income |  |  |  |  |  |  |  |  |  |  | 14.8 | 96.1 | 25.3
Income tax benefit |  |  |  |  |  |  |  |  |  |  | 5.7 | 12.5 | 12.9
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | 20.5 | 108.6 | 38.2
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | 554.5 | 0.0 |
Total income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | 575.0 | 108.6 | 38.5
Net change in pension liability and other accumulated comprehensive items |  |  |  |  |  |  |  |  |  |  | 0.3 | 1.0 | 0.0
Recognition of other comprehensive income from sale of subsidiary |  |  |  |  |  |  |  |  |  |  | 2.9 | 0.0 |
Comprehensive income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | 578.2 | 109.6 | 38.5
Sale of Sirius Group |  |  |  |  |  |  |  |  |  |  |  |  |
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | (0.7) | 363.2 | 0.0
Recognition of other comprehensive income from sale of subsidiary |  |  |  |  |  |  |  |  |  |  |  | 113.3 |
Sale of Sirius Group | Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  | (4.3) | 81.1
Net change in pension liability and other accumulated comprehensive items |  |  |  |  |  |  |  |  |  |  |  | 32.0 |
Sirius Group |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |  |  |
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  |  | 3.7 | 205.0
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  | $ (4.0) |  |  |  | 363.2 |
Sirius Group | Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |  |  |
Earned insurance premiums |  |  |  |  |  |  |  |  |  |  | 0.0 | 240.1 | 847.0
Net investment income |  |  |  |  |  |  |  |  |  |  | 0.0 | 14.4 | 40.7
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  | 0.0 | (1.5) | 15.1
Other revenues |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.6 | (20.6)
Revenues |  |  |  |  |  |  |  |  |  |  | 0.0 | 253.6 | 882.2
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 154.9 | 422.7
Insurance acquisition expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 59.0 | 189.8
Other underwriting expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 30.9 | 107.9
General and administrative expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 10.4 | 27.0
Interest expense |  |  |  |  |  |  |  |  |  |  |  | 7.9 | 26.6
Total expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 263.1 | 774.0
Pre-tax income |  |  |  |  |  |  |  |  |  |  | 0.0 | (9.5) | 108.2
Income tax benefit |  |  |  |  |  |  |  |  |  |  | 0.0 | 3.1 | (27.1)
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | 0.0 | (6.4) |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | (0.7) | 363.2 |
Total income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | (0.7) | 356.8 | 81.1
Net change in pension liability and other accumulated comprehensive items |  |  |  |  |  |  |  |  |  |  | 0.0 | 32.0 | (65.0)
Recognition of other comprehensive income from sale of subsidiary |  |  |  |  |  |  |  |  |  |  | 0.0 | 113.3 |
Comprehensive income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | (0.7) | 502.1 | 16.1
Tranzact |  |  |  |  |  |  |  |  |  |  |  |  |
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Income tax benefit |  | $ (30.2) |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  | $ 51.9 |  |  |  |  |  |  |  |  | 3.2 | 51.9 | 0.0
Tranzact | Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |  |  |
Earned insurance premiums |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 |
Net investment income |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 |
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 |
Other revenues |  |  |  |  |  |  |  |  |  |  | 0.0 | 119.6 |
Revenues |  |  |  |  |  |  |  |  |  |  | 0.0 | 119.6 |
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 |
Insurance acquisition expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 |
Other underwriting expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 |
General and administrative expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 116.7 |
Interest expense |  |  |  |  |  |  |  |  |  |  |  | 3.2 |
Total expenses |  |  |  |  |  |  |  |  |  |  | 0.0 | 119.9 |
Pre-tax income |  |  |  |  |  |  |  |  |  |  | 0.0 | (0.3) |
Income tax benefit |  |  |  |  |  |  |  |  |  |  | 0.0 | 6.4 |
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | 0.0 | 6.1 | (1.9)
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | 3.2 | 51.9 |
Total income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | 3.2 | 58.0 |
Net change in pension liability and other accumulated comprehensive items |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 |
Recognition of other comprehensive income from sale of subsidiary |  |  |  |  |  |  |  |  |  |  | 0.0 | 0.0 |
Comprehensive income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | 3.2 | 58.0 |
Other Operations | Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |  |  |
Earned insurance premiums |  |  |  |  |  |  |  |  |  |  |  |  | 0.0
Net investment income |  |  |  |  |  |  |  |  |  |  |  |  | 0.0
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  |  |  | 0.0
Other revenues |  |  |  |  |  |  |  |  |  |  |  |  | 186.2
Revenues |  |  |  |  |  |  |  |  |  |  |  |  | 186.2
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  |  |  |  |  | 0.0
Insurance acquisition expenses |  |  |  |  |  |  |  |  |  |  |  |  | 0.0
Other underwriting expenses |  |  |  |  |  |  |  |  |  |  |  |  | 0.0
General and administrative expenses |  |  |  |  |  |  |  |  |  |  |  |  | 185.3
Interest expense |  |  |  |  |  |  |  |  |  |  |  |  | 4.0
Total expenses |  |  |  |  |  |  |  |  |  |  |  |  | 189.3
Pre-tax income |  |  |  |  |  |  |  |  |  |  |  |  | (3.1)
Income tax benefit |  |  |  |  |  |  |  |  |  |  |  |  | 0.7
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  |  | (2.4)
Total income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  |  |  | 15.5
Net change in pension liability and other accumulated comprehensive items |  |  |  |  |  |  |  |  |  |  |  |  | 0.0
Comprehensive income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  |  |  | 15.5
Total | Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  |  |  |  |  |
Earned insurance premiums |  |  |  |  |  |  |  |  |  |  | 807.6 | 1,340.7 | 2,023.2
Net investment income |  |  |  |  |  |  |  |  |  |  | 39.7 | 65.0 | 86.6
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  |  | 38.8 | 36.2 | (20.0)
Other revenues |  |  |  |  |  |  |  |  |  |  | 7.7 | 125.7 | 165.0
Revenues |  |  |  |  |  |  |  |  |  |  | 893.8 | 1,567.6 | 2,254.8
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  |  |  | 546.0 | 810.9 | 1,123.4
Insurance acquisition expenses |  |  |  |  |  |  |  |  |  |  | 145.6 | 265.0 | 403.6
Other underwriting expenses |  |  |  |  |  |  |  |  |  |  | 156.2 | 239.9 | 326.1
General and administrative expenses |  |  |  |  |  |  |  |  |  |  | 21.2 | 141.3 | 225.3
Interest expense |  |  |  |  |  |  |  |  |  |  | 10.0 | 24.2 | 46.0
Total expenses |  |  |  |  |  |  |  |  |  |  | 879.0 | 1,481.3 | 2,124.4
Pre-tax income |  |  |  |  |  |  |  |  |  |  | 14.8 | 86.3 | 130.4
Income tax benefit |  |  |  |  |  |  |  |  |  |  | 5.7 | 22.0 | (13.5)
Net (loss) income from discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | 20.5 | 108.3 | 116.9
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  | 557.0 | 415.1 |
Total income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | 577.5 | 523.4 | 135.1
Net change in pension liability and other accumulated comprehensive items |  |  |  |  |  |  |  |  |  |  | 0.3 | 33.0 | (65.0)
Recognition of other comprehensive income from sale of subsidiary |  |  |  |  |  |  |  |  |  |  | 2.9 | 113.3 |
Comprehensive income (loss) from discontinued operations |  |  |  |  |  |  |  |  |  |  | $ 580.7 | $ 669.7 | 70.1
OneBeacon Runoff | Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  |  | 0.3
Esurance & AFI | Discontinued Operations |  |  |  |  |  |  |  |  |  |  |  |  |
Expenses |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) from sale of other discontinued operations, net of tax |  |  |  |  |  |  |  |  |  |  |  |  | $ 17.9

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- Definition Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569616-111683 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=84234705&loc=SL4591552-111686 + Details
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- Definition Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal. + References Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(12)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: 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 Reference 4: 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 5: 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(14)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=65878427&loc=d3e957-107759 Reference 7: 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 8: 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 + Details
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