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Reserves for Losses and Adjustment Expenses Short-duration Insurance Contracts, Claims by Accident Year (Details) | Dec. 31, 2022 USD ($) Integer | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
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Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | $ 3,151,600,000 | $ 4,484,000,000 |  |  |  |  |  |  |  |
Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,772,500,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,513,500,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2013 and subsequent years, net of reinsurance | 259,000,000.0 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2013, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 259,000,000.0 | 289,300,000 |  |  |  |  |  |  |  |
Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,417,100,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 959,800,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2013 and subsequent years, net of reinsurance | 457,300,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2013, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 457,300,000 | 725,600,000 |  |  |  |  |  |  |  |
Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,929,200,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,765,500,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2013 and subsequent years, net of reinsurance | 163,700,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2013, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 163,700,000 | 427,900,000 |  |  |  |  |  |  |  |
Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,970,000,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,298,100,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2013 and subsequent years, net of reinsurance | 671,900,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2013, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 671,900,000 | 808,700,000 |  |  |  |  |  |  |  |
Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 2,854,500,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 2,176,600,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2013 and subsequent years, net of reinsurance | 677,900,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2013, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 677,900,000 | 784,900,000 |  |  |  |  |  |  |  |
Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,628,700,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,057,100,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2013 and subsequent years, net of reinsurance | 571,600,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2013, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 571,600,000 | 975,300,000 |  |  |  |  |  |  |  |
Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 2,344,800,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,994,600,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2013 and subsequent years, net of reinsurance | 350,200,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2013, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 350,200,000 | 472,300,000 |  |  |  |  |  |  |  |
Accident Year 2013 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 106,100,000 | 102,100,000 | $ 109,500,000 | $ 109,300,000 | $ 109,000,000.0 | $ 110,900,000 | $ 109,900,000 | $ 114,200,000 | $ 114,400,000 | $ 126,700,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 0 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 106,100,000 | 106,800,000 | 107,900,000 | 107,600,000 | 105,800,000 | 103,000,000.0 | 98,600,000 | 86,800,000 | 73,700,000 | 37,500,000
Accident Year 2013 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 86,700,000 | 107,800,000 | 100,000,000.0 | 101,400,000 | 101,100,000 | 99,800,000 | 116,800,000 | 111,600,000 | 112,800,000 | 128,600,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,392 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 86,700,000 | 84,000,000.0 | 83,900,000 | 82,000,000.0 | 77,900,000 | 65,900,000 | 51,200,000 | 38,200,000 | 25,100,000 | 2,100,000
Accident Year 2013 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 319,700,000 | 346,500,000 | 338,700,000 | 343,600,000 | 345,000,000.0 | 331,500,000 | 324,300,000 | 340,700,000 | 332,100,000 | 319,400,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,179 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 319,700,000 | 309,000,000.0 | 309,300,000 | 299,100,000 | 283,100,000 | 263,500,000 | 234,100,000 | 203,900,000 | 130,900,000 | 41,200,000
Accident Year 2013 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 82,900,000 | 101,000,000.0 | 95,100,000 | 88,800,000 | 89,900,000 | 98,600,000 | 99,600,000 | 103,100,000 | 98,700,000 | 104,300,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 606 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 82,900,000 | 79,900,000 | 76,400,000 | 73,200,000 | 71,100,000 | 62,800,000 | 64,600,000 | 30,600,000 | 20,600,000 | 7,900,000
Accident Year 2013 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 156,300,000 | 159,500,000 | 162,900,000 | 165,800,000 | 168,500,000 | 171,700,000 | 173,100,000 | 184,100,000 | 193,700,000 | 212,300,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 832 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 156,300,000 | 156,000,000.0 | 156,000,000.0 | 161,600,000 | 160,100,000 | 158,600,000 | 154,100,000 | 142,600,000 | 95,700,000 | 33,900,000
Accident Year 2013 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 151,900,000 | 191,600,000 | 197,900,000 | 200,300,000 | 197,700,000 | 202,300,000 | 219,100,000 | 221,600,000 | 226,700,000 | 211,700,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,700 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 151,900,000 | 144,200,000 | 137,900,000 | 126,000,000.0 | 113,500,000 | 91,800,000 | 64,400,000 | 42,300,000 | 15,700,000 | 3,400,000
Accident Year 2013 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 98,100,000 | 104,800,000 | 108,300,000 | 111,600,000 | 111,900,000 | 115,700,000 | 116,300,000 | 127,700,000 | 135,700,000 | 140,500,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 579 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 98,100,000 | 98,100,000 | 99,000,000.0 | 99,300,000 | 98,400,000 | 98,400,000 | 91,400,000 | 84,400,000 | 68,700,000 | $ 24,300,000
Accident Year 2014 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 131,100,000 | 125,200,000 | 130,100,000 | 130,700,000 | 132,200,000 | 133,000,000.0 | 132,400,000 | 154,900,000 | 162,600,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 9,949 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 131,100,000 | 129,900,000 | 128,700,000 | 127,300,000 | 126,000,000.0 | 122,000,000.0 | 112,500,000 | 85,200,000 | 39,900,000 |
Accident Year 2014 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 107,400,000 | 137,900,000 | 131,800,000 | 134,900,000 | 131,000,000.0 | 124,000,000.0 | 134,200,000 | 122,600,000 | 139,900,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,914 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 107,400,000 | 104,000,000.0 | 105,400,000 | 93,100,000 | 70,100,000 | 57,300,000 | 31,500,000 | 12,600,000 | 2,500,000 |
Accident Year 2014 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 279,100,000 | 317,600,000 | 300,700,000 | 311,400,000 | 304,500,000 | 308,900,000 | 297,200,000 | 312,200,000 | 308,600,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,058 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 279,100,000 | 274,200,000 | 261,700,000 | 249,500,000 | 231,300,000 | 208,600,000 | 188,100,000 | 116,000,000.0 | 53,200,000 |
Accident Year 2014 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 118,900,000 | 124,300,000 | 118,800,000 | 118,000,000.0 | 128,900,000 | 117,700,000 | 127,400,000 | 128,800,000 | 133,200,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 794 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 118,900,000 | 102,300,000 | 90,900,000 | 84,000,000.0 | 78,500,000 | 71,100,000 | 52,700,000 | 30,200,000 | 2,800,000 |
Accident Year 2014 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 138,100,000 | 140,100,000 | 141,200,000 | 141,100,000 | 145,900,000 | 145,700,000 | 157,100,000 | 172,600,000 | 185,800,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 900 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 138,100,000 | 137,800,000 | 137,600,000 | 136,000,000.0 | 137,400,000 | 133,700,000 | 124,400,000 | 98,500,000 | 36,900,000 |
Accident Year 2014 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 144,700,000 | 191,100,000 | 198,000,000.0 | 202,100,000 | 199,000,000.0 | 205,500,000 | 212,300,000 | 204,000,000.0 | 201,800,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,843 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 144,700,000 | 133,000,000.0 | 123,400,000 | 105,900,000 | 85,400,000 | 59,600,000 | 37,400,000 | 13,600,000 | 2,500,000 |
Accident Year 2014 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 105,400,000 | 116,600,000 | 118,000,000.0 | 122,200,000 | 123,600,000 | 120,800,000 | 129,500,000 | 137,500,000 | 149,500,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 622 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 105,400,000 | 104,400,000 | 102,500,000 | 100,900,000 | 98,000,000.0 | 87,800,000 | 79,800,000 | 55,200,000 | $ 16,200,000 |
Accident Year 2015 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 189,200,000 | 179,600,000 | 193,900,000 | 196,900,000 | 196,300,000 | 193,900,000 | 199,000,000.0 | 233,300,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 11,549 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 189,200,000 | 190,400,000 | 188,900,000 | 190,100,000 | 174,100,000 | 165,100,000 | 138,300,000 | 56,300,000 |  |
Accident Year 2015 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 197,200,000 | 250,400,000 | 228,300,000 | 230,100,000 | 197,500,000 | 180,500,000 | 217,900,000 | 197,900,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,775 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 197,200,000 | 174,500,000 | 163,600,000 | 135,000,000.0 | 90,200,000 | 55,100,000 | 16,400,000 | 3,000,000.0 |  |
Accident Year 2015 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 302,700,000 | 327,300,000 | 309,900,000 | 307,200,000 | 283,700,000 | 279,300,000 | 297,000,000.0 | 295,300,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,076 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 302,700,000 | 277,500,000 | 255,500,000 | 220,000,000.0 | 192,100,000 | 172,700,000 | 122,500,000 | 44,600,000 |  |
Accident Year 2015 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 163,900,000 | 189,900,000 | 183,000,000.0 | 188,000,000.0 | 187,100,000 | 183,100,000 | 173,400,000 | 171,900,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,085 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 163,900,000 | 144,100,000 | 137,600,000 | 108,800,000 | 88,600,000 | 69,500,000 | 43,100,000 | 13,500,000 |  |
Accident Year 2015 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 160,600,000 | 177,200,000 | 168,900,000 | 168,900,000 | 153,500,000 | 173,800,000 | 183,700,000 | 210,000,000.0 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,048 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 160,600,000 | 159,500,000 | 155,900,000 | 153,600,000 | 136,700,000 | 124,200,000 | 93,600,000 | 35,600,000 |  |
Accident Year 2015 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 135,100,000 | 198,800,000 | 203,700,000 | 207,500,000 | 209,800,000 | 207,300,000 | 197,600,000 | 191,100,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 2,038 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 135,100,000 | 121,400,000 | 107,300,000 | 88,400,000 | 64,700,000 | 37,800,000 | 17,500,000 | 3,300,000 |  |
Accident Year 2015 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 132,500,000 | 150,000,000.0 | 150,000,000.0 | 154,500,000 | 155,900,000 | 161,100,000 | 166,400,000 | 163,200,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 774 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 132,500,000 | 131,700,000 | 131,700,000 | 128,700,000 | 119,900,000 | 102,500,000 | 55,200,000 | $ 17,300,000 |  |
Accident Year 2016 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 244,800,000 | 233,400,000 | 242,500,000 | 241,300,000 | 240,000,000.0 | 245,000,000.0 | 233,900,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 10,773 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 244,800,000 | 233,700,000 | 228,600,000 | 219,200,000 | 198,100,000 | 166,100,000 | 65,700,000 |  |  |
Accident Year 2016 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 163,300,000 | 247,400,000 | 195,100,000 | 184,200,000 | 177,600,000 | 182,500,000 | 211,500,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,818 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 163,300,000 | 128,800,000 | 106,100,000 | 79,700,000 | 38,600,000 | 22,000,000.0 | 4,000,000.0 |  |  |
Accident Year 2016 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 199,200,000 | 224,300,000 | 217,700,000 | 227,900,000 | 227,500,000 | 229,000,000.0 | 258,800,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,431 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 199,200,000 | 197,300,000 | 189,500,000 | 163,100,000 | 141,300,000 | 81,900,000 | 30,800,000 |  |  |
Accident Year 2016 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 163,200,000 | 189,000,000.0 | 182,900,000 | 199,700,000 | 213,700,000 | 209,300,000 | 188,400,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,244 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 163,200,000 | 133,800,000 | 124,600,000 | 128,700,000 | 100,700,000 | 70,700,000 | 14,800,000 |  |  |
Accident Year 2016 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 229,800,000 | 230,100,000 | 237,700,000 | 242,100,000 | 263,200,000 | 264,600,000 | 264,200,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,307 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 229,800,000 | 230,700,000 | 224,400,000 | 211,600,000 | 200,900,000 | 160,500,000 | 55,800,000 |  |  |
Accident Year 2016 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 174,600,000 | 258,500,000 | 258,500,000 | 251,000,000.0 | 241,000,000.0 | 241,400,000 | 229,300,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 2,153 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 174,600,000 | 145,300,000 | 124,600,000 | 94,800,000 | 62,900,000 | 32,900,000 | 8,900,000 |  |  |
Accident Year 2016 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 197,600,000 | 218,800,000 | 222,600,000 | 227,600,000 | 234,600,000 | 236,600,000 | 235,800,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 938 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 197,600,000 | 201,800,000 | 191,800,000 | 181,700,000 | 163,900,000 | 149,500,000 | $ 58,200,000 |  |  |
Accident Year 2017 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 247,700,000 | 280,900,000 | 248,100,000 | 246,800,000 | 253,700,000 | 290,400,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 9,717 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 247,700,000 | 242,100,000 | 237,900,000 | 217,200,000 | 185,000,000.0 | 95,000,000.0 |  |  |  |
Accident Year 2017 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 154,400,000 | 234,600,000 | 190,500,000 | 173,400,000 | 169,900,000 | 176,300,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 5,495 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 154,400,000 | 110,300,000 | 93,400,000 | 51,200,000 | 22,300,000 | 3,400,000 |  |  |  |
Accident Year 2017 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 205,300,000 | 231,500,000 | 213,700,000 | 206,200,000 | 199,900,000 | 209,300,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 6,059 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 205,300,000 | 155,700,000 | 167,600,000 | 139,600,000 | 97,000,000.0 | 40,000,000.0 |  |  |  |
Accident Year 2017 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 166,700,000 | 208,800,000 | 185,200,000 | 184,500,000 | 179,600,000 | 203,900,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,737 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 166,700,000 | 135,600,000 | 116,200,000 | 83,000,000.0 | 51,000,000.0 | 27,100,000 |  |  |  |
Accident Year 2017 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 447,700,000 | 595,500,000 | 500,400,000 | 511,700,000 | 529,400,000 | 550,700,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,953 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 447,700,000 | 433,700,000 | 437,100,000 | 413,500,000 | 355,400,000 | 123,000,000.0 |  |  |  |
Accident Year 2017 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 147,700,000 | 265,500,000 | 248,900,000 | 249,700,000 | 239,100,000 | 241,000,000.0 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 2,166 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 147,700,000 | 115,700,000 | 96,500,000 | 58,500,000 | 30,200,000 | 8,700,000 |  |  |  |
Accident Year 2017 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 325,900,000 | 364,200,000 | 361,100,000 | 372,100,000 | 388,400,000 | 375,400,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,336 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 325,900,000 | 314,400,000 | 303,800,000 | 268,900,000 | 237,400,000 | $ 94,100,000 |  |  |  |
Accident Year 2018 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 177,300,000 | 196,200,000 | 182,200,000 | 198,100,000 | 196,300,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 8,308 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 177,300,000 | 173,000,000.0 | 176,100,000 | 153,600,000 | 60,300,000 |  |  |  |  |
Accident Year 2018 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 94,400,000 | 169,700,000 | 132,200,000 | 122,500,000 | 119,400,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 5,500 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 94,400,000 | 65,500,000 | 41,400,000 | 27,200,000 | 3,000,000.0 |  |  |  |  |
Accident Year 2018 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 169,700,000 | 238,800,000 | 207,900,000 | 207,100,000 | 170,100,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 5,153 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 169,700,000 | 154,700,000 | 132,600,000 | 104,300,000 | 26,700,000 |  |  |  |  |
Accident Year 2018 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 125,400,000 | 163,200,000 | 151,200,000 | 169,400,000 | 153,700,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,643 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 125,400,000 | 113,300,000 | 97,800,000 | 71,600,000 | 17,400,000 |  |  |  |  |
Accident Year 2018 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 304,500,000 | 571,000,000.0 | 356,000,000.0 | 362,800,000 | 323,500,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,780 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 304,500,000 | 315,300,000 | 296,800,000 | 290,100,000 | 122,100,000 |  |  |  |  |
Accident Year 2018 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 130,400,000 | 264,300,000 | 262,500,000 | 255,000,000.0 | 226,000,000.0 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 2,002 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 130,400,000 | 103,800,000 | 73,000,000.0 | 33,200,000 | 7,100,000 |  |  |  |  |
Accident Year 2018 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 342,100,000 | 419,500,000 | 390,300,000 | 391,900,000 | 392,700,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,403 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 342,100,000 | 328,500,000 | 312,200,000 | 279,000,000.0 | $ 26,700,000 |  |  |  |  |
Accident Year 2019 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 107,800,000 | 104,100,000 | 126,500,000 | 122,500,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 6,852 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 107,800,000 | 99,300,000 | 88,600,000 | 48,000,000.0 |  |  |  |  |  |
Accident Year 2019 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 88,300,000 | 155,300,000 | 144,400,000 | 122,000,000.0 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 5,198 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 88,300,000 | 68,000,000.0 | 16,700,000 | 6,200,000 |  |  |  |  |  |
Accident Year 2019 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 124,000,000.0 | 151,100,000 | 152,800,000 | 145,500,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,662 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 124,000,000.0 | 117,500,000 | 72,400,000 | 33,400,000 |  |  |  |  |  |
Accident Year 2019 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 195,200,000 | 253,900,000 | 259,600,000 | 246,800,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 23,831 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 195,200,000 | 136,800,000 | 86,200,000 | 26,800,000 |  |  |  |  |  |
Accident Year 2019 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 203,600,000 | 358,700,000 | 249,600,000 | 237,300,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,399 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 203,600,000 | 191,400,000 | 143,900,000 | 28,100,000 |  |  |  |  |  |
Accident Year 2019 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 82,100,000 | 252,000,000.0 | 253,100,000 | 232,500,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,567 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 82,100,000 | 60,900,000 | 36,200,000 | 9,100,000 |  |  |  |  |  |
Accident Year 2019 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 423,600,000 | 397,400,000 | 493,400,000 | 470,300,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,537 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 423,600,000 | 398,800,000 | 379,600,000 | $ 272,500,000 |  |  |  |  |  |
Accident Year 2020 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 205,100,000 | 195,900,000 | 199,900,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 24,400,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 7,542 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 150,100,000 | 122,900,000 | 60,100,000 |  |  |  |  |  |  |
Accident Year 2020 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 138,700,000 | 139,300,000 | 131,100,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 72,100,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,755 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 36,100,000 | 9,200,000 | 0 |  |  |  |  |  |  |
Accident Year 2020 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 125,700,000 | 111,200,000 | 110,200,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 17,500,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,856 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 88,600,000 | 66,400,000 | 28,500,000 |  |  |  |  |  |  |
Accident Year 2020 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 336,200,000 | 346,200,000 | 346,300,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 118,000,000.0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 105,947 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 174,200,000 | 120,800,000 | 47,200,000 |  |  |  |  |  |  |
Accident Year 2020 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 348,900,000 | 402,100,000 | 317,500,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 81,000,000.0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,379 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 237,300,000 | 165,500,000 | 41,800,000 |  |  |  |  |  |  |
Accident Year 2020 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 197,900,000 | 233,600,000 | 252,600,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 123,200,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,088 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 44,100,000 | 27,600,000 | 9,100,000 |  |  |  |  |  |  |
Accident Year 2020 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 374,100,000 | 600,000,000.0 | 412,800,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 53,100,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,470 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 290,400,000 | 269,600,000 | $ 212,800,000 |  |  |  |  |  |  |
Accident Year 2021 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 199,500,000 | 204,600,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 38,200,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 6,583 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 118,600,000 | 58,200,000 |  |  |  |  |  |  |  |
Accident Year 2021 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 185,600,000 | 170,500,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 119,700,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 3,356 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 8,800,000 | 3,000,000.00 |  |  |  |  |  |  |  |
Accident Year 2021 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 96,100,000 | 93,000,000.0 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 18,300,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 4,863 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 52,300,000 | 23,500,000 |  |  |  |  |  |  |  |
Accident Year 2021 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 302,800,000 | 284,500,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 170,400,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 34,942 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 90,200,000 | 42,800,000 |  |  |  |  |  |  |  |
Accident Year 2021 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 472,700,000 | 647,300,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 196,900,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,411 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 233,200,000 | 75,000,000.0 |  |  |  |  |  |  |  |
Accident Year 2021 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 215,600,000 | 205,700,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 135,900,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 815 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 37,100,000 | 7,800,000 |  |  |  |  |  |  |  |
Accident Year 2021 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 151,600,000 | 156,600,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 55,800,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,276 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 53,200,000 | $ 28,200,000 |  |  |  |  |  |  |  |
Accident Year 2022 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 163,900,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 62,900,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 4,171 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 40,800,000 |  |  |  |  |  |  |  |  |
Accident Year 2022 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 201,100,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 132,100,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 2,709 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 23,200,000 |  |  |  |  |  |  |  |  |
Accident Year 2022 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 107,700,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 58,800,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 3,810 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 24,900,000 |  |  |  |  |  |  |  |  |
Accident Year 2022 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 314,800,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 265,200,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 3,487 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 17,500,000 |  |  |  |  |  |  |  |  |
Accident Year 2022 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 392,300,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 266,700,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 950 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 65,500,000 |  |  |  |  |  |  |  |  |
Accident Year 2022 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 248,700,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 179,100,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 478 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 9,400,000 |  |  |  |  |  |  |  |  |
Accident Year 2022 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 193,900,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 107,900,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 969 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 25,800,000 |  |  |  |  |  |  |  |  |

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