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Reserves for Losses and Adjustment Expenses Short-duration Insurance Contracts, Claims by Accident Year (Details) $ in Millions | Dec. 31, 2017 USD ($) Integer | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($) | Dec. 31, 2012 USD ($)
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Claims Development [Line Items] |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | $ 5,183.7 |  |  |  |  |
Property Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,154.6 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 824.5 |  |  |  |  |
All outstanding liabilities for 2012 and subsequent years, net of reinsurance | 330.1 |  |  |  |  |
All outstanding liabilities before 2012, net of reinsurance | 2.9 |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 333.0 |  |  |  |  |
Casualty Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 864.5 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 262.8 |  |  |  |  |
All outstanding liabilities for 2012 and subsequent years, net of reinsurance | 601.7 |  |  |  |  |
All outstanding liabilities before 2012, net of reinsurance | 43.0 |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 644.7 |  |  |  |  |
Marine, Aviation and Energy Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,699.9 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,025.4 |  |  |  |  |
All outstanding liabilities for 2012 and subsequent years, net of reinsurance | 674.5 |  |  |  |  |
All outstanding liabilities before 2012, net of reinsurance | 61.4 |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 735.9 |  |  |  |  |
Financial and Professional Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 922.4 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 377.4 |  |  |  |  |
All outstanding liabilities for 2012 and subsequent years, net of reinsurance | 545.0 |  |  |  |  |
All outstanding liabilities before 2012, net of reinsurance | 27.4 |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 572.4 |  |  |  |  |
Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,637.8 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 956.2 |  |  |  |  |
All outstanding liabilities for 2012 and subsequent years, net of reinsurance | 681.6 |  |  |  |  |
All outstanding liabilities before 2012, net of reinsurance | 47.9 |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 729.5 |  |  |  |  |
Casualty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,372.6 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 355.7 |  |  |  |  |
All outstanding liabilities for 2012 and subsequent years, net of reinsurance | 1,016.9 |  |  |  |  |
All outstanding liabilities before 2012, net of reinsurance | 575.6 |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 1,592.5 |  |  |  |  |
Specialty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,222.6 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 702.3 |  |  |  |  |
All outstanding liabilities for 2012 and subsequent years, net of reinsurance | 520.3 |  |  |  |  |
All outstanding liabilities before 2012, net of reinsurance | 55.4 |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 575.7 |  |  |  |  |
Accident Year 2012 | Property Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 154.7 | $ 160.6 | $ 166.2 | $ 167.3 | $ 168.6 | $ 170.7
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0.3 |  |  |  |  |
Number of Reported Claims | Integer | 6,872 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 154.9 | 157.5 | 153.4 | 139.2 | 129.6 | 41.5
Accident Year 2012 | Casualty Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 67.2 | 69.6 | 61.7 | 70.5 | 63.4 | 78.6
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 5.2 |  |  |  |  |
Number of Reported Claims | Integer | 3,536 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 49.7 | 41.3 | 30.0 | 14.3 | 6.7 | 1.3
Accident Year 2012 | Marine, Aviation and Energy Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 329.0 | 333.0 | 347.3 | 326.7 | 307.2 | 269.8
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 33.8 |  |  |  |  |
Number of Reported Claims | Integer | 4,593 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 251.7 | 240.8 | 212.0 | 175.7 | 133.2 | 52.2
Accident Year 2012 | Financial and Professional Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 90.0 | 94.5 | 97.6 | 94.0 | 90.1 | 88.8
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 9.7 |  |  |  |  |
Number of Reported Claims | Integer | 593 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 70.7 | 65.4 | 59.5 | 50.8 | 39.6 | 22.8
Accident Year 2012 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 280.4 | 283.4 | 280.0 | 287.2 | 304.2 | 281.3
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 19.3 |  |  |  |  |
Number of Reported Claims | Integer | 797 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 228.6 | 217.5 | 209.9 | 189.5 | 136.2 | 35.7
Accident Year 2012 | Casualty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 235.6 | 234.8 | 238.0 | 246.6 | 235.2 | 236.9
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 66.1 |  |  |  |  |
Number of Reported Claims | Integer | 2,173 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 118.5 | 97.1 | 65.8 | 42.2 | 17.9 | 2.2
Accident Year 2012 | Specialty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 176.3 | 176.0 | 177.4 | 191.1 | 201.7 | 178.5
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 10.5 |  |  |  |  |
Number of Reported Claims | Integer | 739 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 152.2 | 146.9 | 141.4 | 131.2 | 95.8 | $ 25.7
Accident Year 2013 | Property Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 114.3 | 113.3 | 117.5 | 117.9 | 130.8 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 4.9 |  |  |  |  |
Number of Reported Claims | Integer | 5,100 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 106.4 | 101.8 | 89.7 | 76.4 | 39.2 |
Accident Year 2013 | Casualty Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 104.4 | 121.4 | 115.9 | 117.5 | 134.1 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 13.6 |  |  |  |  |
Number of Reported Claims | Integer | 3,852 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 69.0 | 53.5 | 39.8 | 26.0 | 2.3 |
Accident Year 2013 | Marine, Aviation and Energy Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 333.3 | 326.3 | 342.9 | 334.2 | 321.4 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 17.4 |  |  |  |  |
Number of Reported Claims | Integer | 4,979 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 265.0 | 235.7 | 205.3 | 131.8 | 41.6 |
Accident Year 2013 | Financial and Professional Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 101.6 | 102.3 | 105.6 | 101.2 | 106.6 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 15.2 |  |  |  |  |
Number of Reported Claims | Integer | 603 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 64.5 | 66.0 | 31.6 | 21.5 | 8.1 |
Accident Year 2013 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 180.8 | 182.3 | 193.9 | 203.0 | 220.5 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 4.4 |  |  |  |  |
Number of Reported Claims | Integer | 945 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 166.8 | 162.0 | 149.7 | 100.3 | 34.9 |
Accident Year 2013 | Casualty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 208.4 | 225.8 | 228.4 | 232.9 | 217.5 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 62.2 |  |  |  |  |
Number of Reported Claims | Integer | 2,034 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 93.7 | 65.5 | 43.2 | 16.0 | 3.5 |
Accident Year 2013 | Specialty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 121.7 | 122.5 | 134.5 | 141.9 | 146.9 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 7.7 |  |  |  |  |
Number of Reported Claims | Integer | 620 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 103.5 | 96.4 | 89.1 | 72.7 | $ 25.4 |
Accident Year 2014 | Property Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 135.4 | 134.7 | 157.9 | 166.2 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 3.0 |  |  |  |  |
Number of Reported Claims | Integer | 8,779 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 124.2 | 114.5 | 87.0 | 40.5 |  |
Accident Year 2014 | Casualty Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 130.9 | 140.5 | 128.6 | 146.4 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 20.4 |  |  |  |  |
Number of Reported Claims | Integer | 4,312 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 60.4 | 33.1 | 13.6 | 2.7 |  |
Accident Year 2014 | Marine, Aviation and Energy Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 310.9 | 299.3 | 314.5 | 310.1 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 45.3 |  |  |  |  |
Number of Reported Claims | Integer | 4,768 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 210.2 | 189.5 | 117.0 | 53.6 |  |
Accident Year 2014 | Financial and Professional Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 121.4 | 131.3 | 132.6 | 136.4 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 35.2 |  |  |  |  |
Number of Reported Claims | Integer | 852 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 72.8 | 54.1 | 30.9 | 3.0 |  |
Accident Year 2014 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 152.4 | 164.0 | 180.4 | 191.7 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 4.1 |  |  |  |  |
Number of Reported Claims | Integer | 1,016 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 139.4 | 129.2 | 102.3 | 37.8 |  |
Accident Year 2014 | Casualty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 214.0 | 220.8 | 212.0 | 208.7 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 84.5 |  |  |  |  |
Number of Reported Claims | Integer | 1,842 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 60.9 | 38.2 | 14.1 | 2.6 |  |
Accident Year 2014 | Specialty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 126.0 | 135.2 | 143.4 | 154.4 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 15.6 |  |  |  |  |
Number of Reported Claims | Integer | 667 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 91.3 | 83.1 | 57.9 | $ 17.0 |  |
Accident Year 2015 | Property Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 201.8 | 207.3 | 241.9 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 4.7 |  |  |  |  |
Number of Reported Claims | Integer | 10,431 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 172.1 | 144.0 | 57.5 |  |  |
Accident Year 2015 | Casualty Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 188.0 | 225.5 | 205.5 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 64.7 |  |  |  |  |
Number of Reported Claims | Integer | 4,954 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 57.0 | 17.2 | 3.2 |  |  |
Accident Year 2015 | Marine, Aviation and Energy Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 283.3 | 301.0 | 297.9 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 37.9 |  |  |  |  |
Number of Reported Claims | Integer | 4,356 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 174.9 | 123.7 | 45.1 |  |  |
Accident Year 2015 | Financial and Professional Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 187.2 | 177.2 | 175.9 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 76.7 |  |  |  |  |
Number of Reported Claims | Integer | 1,138 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 70.4 | 43.7 | 13.9 |  |  |
Accident Year 2015 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 181.6 | 191.4 | 219.4 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 18.7 |  |  |  |  |
Number of Reported Claims | Integer | 1,135 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 130.0 | 96.9 | 36.2 |  |  |
Accident Year 2015 | Casualty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 214.6 | 205.3 | 197.9 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 103.0 |  |  |  |  |
Number of Reported Claims | Integer | 1,648 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 39.2 | 18.5 | 3.6 |  |  |
Accident Year 2015 | Specialty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 168.8 | 174.3 | 169.7 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 29.4 |  |  |  |  |
Number of Reported Claims | Integer | 826 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 106.5 | 58.1 | $ 18.1 |  |  |
Accident Year 2016 | Property Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 250.7 | 239.9 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 14.7 |  |  |  |  |
Number of Reported Claims | Integer | 9,514 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 169.7 | 67.3 |  |  |  |
Accident Year 2016 | Casualty Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 190.6 | 219.4 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 117.9 |  |  |  |  |
Number of Reported Claims | Integer | 5,084 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 23.1 | 4.2 |  |  |  |
Accident Year 2016 | Marine, Aviation and Energy Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 231.9 | 219.4 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 49.5 |  |  |  |  |
Number of Reported Claims | Integer | 4,572 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 83.2 | 30.9 |  |  |  |
Accident Year 2016 | Financial and Professional Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 213.6 | 193.0 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 121.1 |  |  |  |  |
Number of Reported Claims | Integer | 1,365 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 71.7 | 15.4 |  |  |  |
Accident Year 2016 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 277.8 | 277.9 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 35.1 |  |  |  |  |
Number of Reported Claims | Integer | 1,297 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 167.2 | 58.0 |  |  |  |
Accident Year 2016 | Casualty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 250.5 | 237.7 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 156.2 |  |  |  |  |
Number of Reported Claims | Integer | 1,151 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 34.3 | 9.6 |  |  |  |
Accident Year 2016 | Specialty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 244.6 | 243.2 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 49.5 |  |  |  |  |
Number of Reported Claims | Integer | 844 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 153.1 | $ 59.6 |  |  |  |
Accident Year 2017 | Property Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 297.7 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 51.3 |  |  |  |  |
Number of Reported Claims | Integer | 6,249 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 97.2 |  |  |  |  |
Accident Year 2017 | Casualty Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 183.4 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 153.0 |  |  |  |  |
Number of Reported Claims | Integer | 4,447 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 3.6 |  |  |  |  |
Accident Year 2017 | Marine, Aviation and Energy Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 211.5 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 70.0 |  |  |  |  |
Number of Reported Claims | Integer | 3,993 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 40.4 |  |  |  |  |
Accident Year 2017 | Financial and Professional Insurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 208.6 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 159.4 |  |  |  |  |
Number of Reported Claims | Integer | 1,743 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 27.3 |  |  |  |  |
Accident Year 2017 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 564.8 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 216.1 |  |  |  |  |
Number of Reported Claims | Integer | 1,366 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 124.2 |  |  |  |  |
Accident Year 2017 | Casualty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 249.5 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 215.9 |  |  |  |  |
Number of Reported Claims | Integer | 476 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 9.1 |  |  |  |  |
Accident Year 2017 | Specialty Reinsurance |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 385.2 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 211.6 |  |  |  |  |
Number of Reported Claims | Integer | 763 |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 95.7 |  |  |  |  |

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