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Segment Information (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
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, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Percentage of par value of policy reinsured | 15.00% |  |  |  |  |  |  |  | 15.00% |  |
Earned insurance premiums |  |  |  |  |  |  |  |  | $ 1,114.0 | $ 1,188.2 | $ 1,185.0
Net investment income |  |  |  |  |  |  |  |  | 86.8 | 60.8 | 59.5
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 10.3 | 225.4 | 78.5
Other revenue |  |  |  |  |  |  |  |  | 149.6 | 147.3 | 88.1
Total revenues | $ 268.2 | $ 365.0 | $ 358.2 | $ 369.3 | $ 602.6 | $ 296.1 | $ 368.7 | $ 354.3 | 1,360.7 | 1,621.7 | 1,411.1
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 664.0 | 708.9 | 824.0
Insurance acquisition expenses |  |  |  |  |  |  |  |  | 211.6 | 220.1 | 206.2
Other underwriting expenses |  |  |  |  |  |  |  |  | 209.5 | 218.6 | 179.6
General and administrative expenses |  |  |  |  |  |  |  |  | 299.9 | 302.2 | 216.5
Amortization of Intangible Assets |  |  |  |  |  |  |  |  | 12.5 | 10.6 | 8.3
Interest expense on debt |  |  |  |  |  |  |  |  | 16.1 | 14.6 | 14.2
Total expenses | 335.0 | 345.0 | 360.3 | 360.8 | 356.3 | 383.0 | 373.8 | 351.3 | 1,401.1 | 1,464.4 | 1,440.5
Pre-tax (loss) income from continuing operations | $ (66.8) | $ 20.0 | $ (2.1) | $ 8.5 | $ 246.3 | $ (86.9) | $ (5.1) | $ 3.0 | (40.4) | 157.3 | (29.4)
Segment Reconciling Items [Member] |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
General and administrative expenses |  |  |  |  |  |  |  |  | 287.4 | 291.6 | 208.2
OneBeacon |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Earned insurance premiums |  |  |  |  |  |  |  |  | 1,100.6 | 1,176.2 | 1,177.1
Net investment income |  |  |  |  |  |  |  |  | 50.6 | 45.9 | 43.4
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 37.7 | (35.1) | 40.4
Other revenue |  |  |  |  |  |  |  |  | 5.5 | (0.6) | 5.8
Total revenues |  |  |  |  |  |  |  |  | 1,194.4 | 1,186.4 | 1,266.7
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 656.0 | 700.7 | 815.1
Insurance acquisition expenses |  |  |  |  |  |  |  |  | 206.0 | 213.8 | 203.3
Other underwriting expenses |  |  |  |  |  |  |  |  | 209.0 | 218.2 | 179.2
Interest expense on debt |  |  |  |  |  |  |  |  | 13.1 | 13.0 | 13.0
Total expenses |  |  |  |  |  |  |  |  | 1,098.3 | 1,161.1 | 1,224.4
Pre-tax (loss) income from continuing operations |  |  |  |  |  |  |  |  | 96.1 | 25.3 | 42.3
OneBeacon | Segment Reconciling Items [Member] |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
General and administrative expenses |  |  |  |  |  |  |  |  | 13.0 | 14.1 | 12.4
BAM |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Earned insurance premiums |  |  |  |  |  |  |  |  | 1.5 | 0.8 | 0.4
Net investment income |  |  |  |  |  |  |  |  | 6.8 | 4.2 | 5.7
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 0.6 | 0.9 | 6.6
Other revenue |  |  |  |  |  |  |  |  | 1.1 | 0.7 | 0.6
Total revenues |  |  |  |  |  |  |  |  | (7.8) | (9.2) | (2.4)
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
Insurance acquisition expenses |  |  |  |  |  |  |  |  | 2.5 | 2.3 | 1.8
Other underwriting expenses |  |  |  |  |  |  |  |  | 0.4 | 0.4 | 0.4
Interest expense on debt |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
Total expenses |  |  |  |  |  |  |  |  | 41.1 | 38.1 | 38.1
Pre-tax (loss) income from continuing operations |  |  |  |  |  |  |  |  | (48.9) | (47.3) | (40.5)
BAM | Segment Reconciling Items [Member] |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
General and administrative expenses |  |  |  |  |  |  |  |  | $ 38.2 | 35.4 | 35.9
HG Global |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Percentage of par value of policy reinsured | 15.00% |  |  |  |  |  |  |  | 15.00% |  |
Earned insurance premiums |  |  |  |  |  |  |  |  | $ 4.4 | 2.5 | 1.4
Net investment income |  |  |  |  |  |  |  |  | 2.2 | 1.9 | 1.4
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 0.1 | (0.3) | 1.7
Other revenue |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
Total revenues |  |  |  |  |  |  |  |  | 24.5 | 19.9 | 20.2
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
Insurance acquisition expenses |  |  |  |  |  |  |  |  | 0.9 | 0.6 | 0.3
Other underwriting expenses |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
Interest expense on debt |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
Total expenses |  |  |  |  |  |  |  |  | 2.3 | 2.0 | 1.9
Pre-tax (loss) income from continuing operations |  |  |  |  |  |  |  |  | 22.2 | 17.9 | 18.3
HG Global | Segment Reconciling Items [Member] |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
General and administrative expenses |  |  |  |  |  |  |  |  | 1.4 | 1.4 | 1.6
Other Segments |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Earned insurance premiums |  |  |  |  |  |  |  |  | 7.5 | 8.7 | 6.1
Net investment income |  |  |  |  |  |  |  |  | 27.2 | 8.8 | 9.0
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | (28.1) | 259.9 | 29.8
Other revenue |  |  |  |  |  |  |  |  | 143.0 | 147.2 | 81.7
Total revenues |  |  |  |  |  |  |  |  | 149.6 | 424.6 | 126.6
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 8.0 | 8.2 | 8.9
Insurance acquisition expenses |  |  |  |  |  |  |  |  | 2.2 | 3.4 | 0.8
Other underwriting expenses |  |  |  |  |  |  |  |  | 0.1 | 0.0 | 0.0
Interest expense on debt |  |  |  |  |  |  |  |  | 3.0 | 1.6 | 1.2
Total expenses |  |  |  |  |  |  |  |  | 259.4 | 263.2 | 176.1
Pre-tax (loss) income from continuing operations |  |  |  |  |  |  |  |  | (109.8) | 161.4 | (49.5)
Other Segments | Segment Reconciling Items [Member] |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
General and administrative expenses |  |  |  |  |  |  |  |  | 234.8 | 240.7 | 158.3
General and Administrative Expense [Member] |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Amortization of Intangible Assets |  |  |  |  |  |  |  |  | 12.5 | 10.6 | 8.3
General and Administrative Expense [Member] | OneBeacon |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Amortization of Intangible Assets |  |  |  |  |  |  |  |  | 1.2 | 1.3 | 1.4
General and Administrative Expense [Member] | BAM |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Amortization of Intangible Assets |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
General and Administrative Expense [Member] | HG Global |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Amortization of Intangible Assets |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
General and Administrative Expense [Member] | Other Segments |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Amortization of Intangible Assets |  |  |  |  |  |  |  |  | 11.3 | 9.3 | 6.9
Symetra | Other Segments |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  |  | 258.8 |
MediaAlpha [Member] | Other Segments |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Other revenue |  |  |  |  |  |  |  |  | 116.5 | 105.5 | 65.3
General and administrative expenses |  |  |  |  |  |  |  |  | 109.6 | 99.0 | 60.6
Surplus Note |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Net investment income |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
Surplus Note | OneBeacon |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Net investment income |  |  |  |  |  |  |  |  | 0.0 | 0.0 | 0.0
Surplus Note | BAM |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Net investment income |  |  |  |  |  |  |  |  | (17.8) | (15.8) | (15.7)
Surplus Note | HG Global |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Net investment income |  |  |  |  |  |  |  |  | 17.8 | 15.8 | 15.7
Surplus Note | Other Segments |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Net investment income |  |  |  |  |  |  |  |  | $ 0.0 | $ 0.0 | $ 0.0

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