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Reserves for Losses and Adjustment Expenses Short-duration Insurance Contracts, Claims by Accident Year (Details) | Dec. 31, 2024 USD ($) Integer | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
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Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | $ 4,116,600,000 | $ 3,629,600,000 |  |  |  |  |  |  |  |
Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,816,400,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,547,500,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2015 and subsequent years, net of reinsurance | 268,900,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2015, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 268,900,000 | 270,800,000 |  |  |  |  |  |  |  |
Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,477,200,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 721,200,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2015 and subsequent years, net of reinsurance | 756,000,000.0 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2015, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 756,000,000.0 | 636,500,000 |  |  |  |  |  |  |  |
Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,434,400,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,213,100,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2015 and subsequent years, net of reinsurance | 221,300,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2015, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 221,300,000 | 194,500,000 |  |  |  |  |  |  |  |
Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 2,338,700,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,357,400,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2015 and subsequent years, net of reinsurance | 981,300,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2015, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 981,300,000 | 837,600,000 |  |  |  |  |  |  |  |
Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 2,925,200,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 2,364,600,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2015 and subsequent years, net of reinsurance | 560,600,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2015, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 560,600,000 | 562,300,000 |  |  |  |  |  |  |  |
Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,691,100,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 805,200,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2015 and subsequent years, net of reinsurance | 885,900,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2015, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 885,900,000 | 733,600,000 |  |  |  |  |  |  |  |
Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 2,339,100,000 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | 1,896,500,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities for 2015 and subsequent years, net of reinsurance | 442,600,000 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2015, net of reinsurance | 0 |  |  |  |  |  |  |  |  |
Liability for claims and claim adjustment expenses, net of reinsurance | 442,600,000 | 394,300,000 |  |  |  |  |  |  |  |
Accident Year 2015 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 192,300,000 | 192,300,000 | $ 192,300,000 | $ 192,300,000 | $ 196,300,000 | $ 199,400,000 | $ 198,800,000 | $ 196,500,000 | $ 201,700,000 | $ 236,000,000.0
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 11,558 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 192,300,000 | 192,300,000 | 192,300,000 | 192,300,000 | 191,300,000 | 192,600,000 | 176,400,000 | 167,400,000 | 140,200,000 | 56,700,000
Accident Year 2015 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 178,900,000 | 178,900,000 | 178,900,000 | 255,600,000 | 230,300,000 | 232,000,000.0 | 199,400,000 | 182,300,000 | 219,800,000 | 199,800,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,843 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 178,900,000 | 178,900,000 | 178,900,000 | 178,900,000 | 165,000,000.0 | 136,200,000 | 91,000,000.0 | 55,700,000 | 16,600,000 | 3,100,000
Accident Year 2015 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 266,000,000.0 | 266,000,000.0 | 266,000,000.0 | 317,200,000 | 309,900,000 | 307,200,000 | 283,600,000 | 278,700,000 | 296,000,000.0 | 294,200,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,079 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 266,000,000.0 | 266,000,000.0 | 266,000,000.0 | 267,500,000 | 255,800,000 | 220,100,000 | 192,200,000 | 172,600,000 | 122,200,000 | 44,500,000
Accident Year 2015 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 144,400,000 | 144,400,000 | 144,400,000 | 195,800,000 | 183,000,000.0 | 188,000,000.0 | 187,000,000.0 | 183,100,000 | 173,000,000.0 | 171,700,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,082 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 144,400,000 | 144,400,000 | 144,400,000 | 150,100,000 | 137,700,000 | 108,800,000 | 88,700,000 | 69,700,000 | 43,200,000 | 13,600,000
Accident Year 2015 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 151,900,000 | 151,900,000 | 151,900,000 | 173,000,000.0 | 166,900,000 | 166,800,000 | 151,400,000 | 171,500,000 | 181,100,000 | 206,700,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,045 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 151,900,000 | 151,900,000 | 151,900,000 | 155,600,000 | 154,200,000 | 151,900,000 | 135,000,000.0 | 122,000,000.0 | 92,400,000 | 35,600,000
Accident Year 2015 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 115,200,000 | 115,200,000 | 115,200,000 | 192,200,000 | 201,900,000 | 205,500,000 | 207,600,000 | 204,900,000 | 195,200,000 | 188,900,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 2,090 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 115,200,000 | 115,200,000 | 115,200,000 | 115,200,000 | 106,800,000 | 88,000,000.0 | 64,400,000 | 37,500,000 | 17,400,000 | 3,300,000
Accident Year 2015 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 129,200,000 | 129,200,000 | 129,200,000 | 147,900,000 | 148,100,000 | 152,500,000 | 154,000,000.0 | 159,300,000 | 164,500,000 | 161,600,000
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 775 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 129,200,000 | 129,200,000 | 129,200,000 | 129,900,000 | 130,100,000 | 127,100,000 | 118,600,000 | 101,600,000 | 54,600,000 | $ 17,200,000
Accident Year 2016 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 232,600,000 | 232,600,000 | 232,600,000 | 233,400,000 | 244,400,000 | 243,100,000 | 241,800,000 | 246,800,000 | 235,800,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 10,752 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 232,600,000 | 232,600,000 | 232,600,000 | 233,400,000 | 230,300,000 | 221,000,000.0 | 199,500,000 | 167,300,000 | 66,300,000 |
Accident Year 2016 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 122,900,000 | 122,900,000 | 122,900,000 | 241,300,000 | 196,900,000 | 185,800,000 | 179,400,000 | 184,300,000 | 213,300,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,850 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 122,900,000 | 122,900,000 | 122,900,000 | 122,000,000.0 | 107,200,000 | 80,600,000 | 39,100,000 | 22,300,000 | 4,100,000 |
Accident Year 2016 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 196,200,000 | 196,200,000 | 196,200,000 | 218,600,000 | 216,800,000 | 227,000,000.0 | 226,400,000 | 228,100,000 | 257,800,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,437 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 196,200,000 | 196,200,000 | 196,200,000 | 191,700,000 | 188,700,000 | 162,300,000 | 140,600,000 | 81,700,000 | 30,900,000 |
Accident Year 2016 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 133,000,000.0 | 133,000,000.0 | 133,000,000.0 | 184,300,000 | 182,800,000 | 199,600,000 | 213,500,000 | 209,100,000 | 188,100,000 |
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 | $ 133,000,000.0 | 133,000,000.0 | 133,000,000.0 | 129,200,000 | 124,600,000 | 128,700,000 | 100,700,000 | 70,600,000 | 14,800,000 |
Accident Year 2016 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 221,700,000 | 221,700,000 | 221,700,000 | 224,300,000 | 231,800,000 | 236,300,000 | 256,800,000 | 257,200,000 | 257,200,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,281 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 221,700,000 | 221,700,000 | 221,700,000 | 224,300,000 | 219,500,000 | 207,000,000.0 | 196,800,000 | 157,100,000 | 54,700,000 |
Accident Year 2016 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 135,200,000 | 135,200,000 | 135,200,000 | 246,600,000 | 255,800,000 | 248,400,000 | 238,300,000 | 238,700,000 | 226,600,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 2,268 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 135,200,000 | 135,200,000 | 135,200,000 | 135,400,000 | 123,800,000 | 94,200,000 | 62,400,000 | 32,600,000 | 8,700,000 |
Accident Year 2016 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 185,800,000 | 185,800,000 | 185,800,000 | 208,800,000 | 221,000,000.0 | 225,900,000 | 232,700,000 | 234,700,000 | 233,900,000 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 943 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 185,800,000 | 185,800,000 | 185,800,000 | 192,000,000.0 | 190,600,000 | 180,500,000 | 162,700,000 | 148,800,000 | $ 57,900,000 |
Accident Year 2017 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 180,400,000 | 180,400,000 | 180,400,000 | 272,100,000 | 250,100,000 | 248,800,000 | 255,600,000 | 292,500,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 9,711 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 180,400,000 | 180,400,000 | 180,400,000 | 233,600,000 | 239,700,000 | 219,000,000.0 | 186,400,000 | 95,500,000 |  |
Accident Year 2017 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 60,200,000 | 60,200,000 | 60,200,000 | 213,300,000 | 192,500,000 | 175,100,000 | 171,400,000 | 177,900,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 5,536 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 60,200,000 | 60,200,000 | 60,200,000 | 88,100,000 | 94,800,000 | 51,800,000 | 22,500,000 | 3,500,000 |  |
Accident Year 2017 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 135,300,000 | 135,300,000 | 135,300,000 | 224,900,000 | 213,600,000 | 206,000,000.0 | 199,500,000 | 208,500,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 6,080 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 135,300,000 | 135,300,000 | 135,300,000 | 149,300,000 | 167,700,000 | 139,700,000 | 97,100,000 | 40,000,000.0 |  |
Accident Year 2017 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 134,400,000 | 134,400,000 | 134,400,000 | 206,800,000 | 185,200,000 | 184,600,000 | 179,700,000 | 203,700,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,758 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 134,400,000 | 134,400,000 | 134,400,000 | 133,500,000 | 115,800,000 | 82,700,000 | 50,900,000 | 27,000,000.0 |  |
Accident Year 2017 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 431,800,000 | 431,800,000 | 431,800,000 | 568,900,000 | 496,900,000 | 508,100,000 | 524,900,000 | 544,800,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,940 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 431,800,000 | 431,800,000 | 431,800,000 | 407,300,000 | 434,100,000 | 410,700,000 | 353,300,000 | 122,600,000 |  |
Accident Year 2017 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 109,600,000 | 109,600,000 | 109,600,000 | 257,700,000 | 246,300,000 | 246,900,000 | 236,400,000 | 238,400,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 2,346 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 109,600,000 | 109,600,000 | 109,600,000 | 109,500,000 | 96,000,000.0 | 58,100,000 | 29,900,000 | 8,700,000 |  |
Accident Year 2017 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 303,300,000 | 303,300,000 | 303,300,000 | 352,600,000 | 359,100,000 | 370,000,000.0 | 385,900,000 | 372,600,000 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,337 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 303,300,000 | 303,300,000 | 303,300,000 | 303,300,000 | 302,400,000 | 267,800,000 | 236,600,000 | $ 93,800,000 |  |
Accident Year 2018 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 184,400,000 | 184,400,000 | 184,400,000 | 194,700,000 | 184,800,000 | 200,800,000 | 198,700,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 8,202 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 184,400,000 | 184,400,000 | 184,400,000 | 172,100,000 | 178,400,000 | 156,100,000 | 60,900,000 |  |  |
Accident Year 2018 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 42,600,000 | 42,600,000 | 42,600,000 | 162,600,000 | 133,300,000 | 123,300,000 | 120,400,000 |  |  |
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 | $ 42,600,000 | 42,600,000 | 42,600,000 | 57,300,000 | 42,100,000 | 27,500,000 | 3,100,000 |  |  |
Accident Year 2018 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 149,900,000 | 149,900,000 | 149,900,000 | 234,500,000 | 207,500,000 | 206,400,000 | 169,300,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 5,201 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 149,900,000 | 149,900,000 | 149,900,000 | 150,500,000 | 132,500,000 | 104,200,000 | 26,600,000 |  |  |
Accident Year 2018 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 109,700,000 | 109,700,000 | 109,700,000 | 159,700,000 | 150,700,000 | 169,300,000 | 153,600,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,645 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 109,700,000 | 109,700,000 | 109,700,000 | 109,800,000 | 97,600,000 | 72,300,000 | 18,300,000 |  |  |
Accident Year 2018 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 283,000,000.0 | 283,000,000.0 | 283,000,000.0 | 511,700,000 | 320,500,000 | 329,700,000 | 303,700,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,804 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 283,000,000.0 | 283,000,000.0 | 283,000,000.0 | 258,000,000.0 | 265,600,000 | 266,800,000 | 121,400,000 |  |  |
Accident Year 2018 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 91,700,000 | 91,700,000 | 91,700,000 | 251,200,000 | 260,600,000 | 252,600,000 | 223,700,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 2,262 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 91,700,000 | 91,700,000 | 91,700,000 | 91,800,000 | 72,600,000 | 33,000,000.0 | 7,000,000.0 |  |  |
Accident Year 2018 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 322,300,000 | 322,300,000 | 322,300,000 | 412,000,000.0 | 387,400,000 | 388,900,000 | 389,300,000 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,428 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 322,300,000 | 322,300,000 | 322,300,000 | 322,100,000 | 310,600,000 | 277,900,000 | $ 26,500,000 |  |  |
Accident Year 2019 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 189,000,000.0 | 189,000,000.0 | 189,000,000.0 | 102,200,000 | 128,300,000 | 124,300,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 6,863 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 189,000,000.0 | 189,000,000.0 | 189,000,000.0 | 97,700,000 | 89,900,000 | 48,500,000 |  |  |  |
Accident Year 2019 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 48,100,000 | 48,100,000 | 48,100,000 | 152,000,000.0 | 145,200,000 | 122,900,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 5,217 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 48,100,000 | 48,100,000 | 48,100,000 | 63,700,000 | 17,200,000 | 6,200,000 |  |  |  |
Accident Year 2019 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 107,000,000.0 | 107,000,000.0 | 107,000,000.0 | 122,700,000 | 152,200,000 | 144,600,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,699 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 107,000,000.0 | 107,000,000.0 | 107,000,000.0 | 89,300,000 | 72,100,000 | 33,300,000 |  |  |  |
Accident Year 2019 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 130,800,000 | 130,800,000 | 130,800,000 | 236,300,000 | 258,100,000 | 245,900,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 23,819 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 130,800,000 | 130,800,000 | 130,800,000 | 120,400,000 | 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 | 157,500,000 | 157,500,000 | 157,500,000 | 316,300,000 | 225,000,000.0 | 209,900,000 |  |  |  |
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 | $ 157,500,000 | 157,500,000 | 157,500,000 | 158,800,000 | 134,100,000 | 28,000,000.0 |  |  |  |
Accident Year 2019 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 52,200,000 | 52,200,000 | 52,200,000 | 241,500,000 | 250,800,000 | 230,100,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,939 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 52,200,000 | 52,200,000 | 52,200,000 | 52,000,000.0 | 36,000,000.0 | 9,100,000 |  |  |  |
Accident Year 2019 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 398,600,000 | 398,600,000 | 398,600,000 | 396,900,000 | 491,700,000 | 468,600,000 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,557 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 398,600,000 | 398,600,000 | 398,600,000 | 396,900,000 | 379,000,000.0 | $ 272,200,000 |  |  |  |
Accident Year 2020 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 213,000,000.0 | 212,500,000 | 207,000,000.0 | 197,500,000 | 202,000,000.0 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 23,000,000.0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 7,648 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 178,200,000 | 169,000,000.0 | 151,200,000 | 123,700,000 | 60,700,000 |  |  |  |  |
Accident Year 2020 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 151,800,000 | 145,500,000 | 139,400,000 | 140,400,000 | 131,800,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 38,100,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,888 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 91,500,000 | 61,100,000 | 36,000,000.0 | 9,300,000 | 0 |  |  |  |  |
Accident Year 2020 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 150,900,000 | 126,100,000 | 125,000,000.0 | 110,700,000 | 109,600,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 33,500,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,866 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 109,200,000 | 100,900,000 | 88,500,000 | 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 | 352,200,000 | 349,800,000 | 336,200,000 | 345,500,000 | 345,200,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 73,700,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 106,042 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 240,000,000.0 | 225,000,000.0 | 173,700,000 | 120,800,000 | 47,300,000 |  |  |  |  |
Accident Year 2020 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 365,200,000 | 352,900,000 | 340,700,000 | 394,200,000 | 312,200,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 5,200,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,436 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 306,000,000.0 | 306,000,000.0 | 232,700,000 | 162,200,000 | 41,100,000 |  |  |  |  |
Accident Year 2020 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 187,200,000 | 178,200,000 | 195,800,000 | 231,200,000 | 250,200,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 42,400,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,563 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 100,900,000 | 70,700,000 | 43,500,000 | 27,300,000 | 8,900,000 |  |  |  |  |
Accident Year 2020 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 369,500,000 | 377,100,000 | 372,900,000 | 598,700,000 | 411,200,000 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 15,100,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,519 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 333,000,000.0 | 310,100,000 | 289,600,000 | 269,200,000 | $ 212,500,000 |  |  |  |  |
Accident Year 2021 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 191,100,000 | 194,600,000 | 201,000,000.0 | 206,300,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 9,200,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 6,770 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 162,900,000 | 150,600,000 | 119,200,000 | 58,400,000 |  |  |  |  |  |
Accident Year 2021 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 194,600,000 | 196,100,000 | 186,900,000 | 171,900,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 81,700,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,679 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 91,300,000 | 53,500,000 | 23,300,000 | 3,100,000 |  |  |  |  |  |
Accident Year 2021 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 96,500,000 | 94,700,000 | 95,100,000 | 92,200,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 11,900,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 4,787 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 70,400,000 | 64,400,000 | 52,200,000 | 23,500,000 |  |  |  |  |  |
Accident Year 2021 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 294,800,000 | 293,500,000 | 301,600,000 | 283,900,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 86,200,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 34,963 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 161,900,000 | 131,100,000 | 90,000,000.0 | 43,100,000 |  |  |  |  |  |
Accident Year 2021 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 472,500,000 | 479,800,000 | 461,200,000 | 637,700,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 4,900,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,518 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 414,800,000 | 351,500,000 | 229,200,000 | 74,600,000 |  |  |  |  |  |
Accident Year 2021 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 199,400,000 | 203,600,000 | 213,800,000 | 203,500,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 63,200,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,594 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 96,400,000 | 63,300,000 | 36,800,000 | 7,700,000 |  |  |  |  |  |
Accident Year 2021 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 136,400,000 | 140,000,000.0 | 150,300,000 | 155,200,000 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 24,300,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,385 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 87,900,000 | 75,200,000 | 52,800,000 | $ 28,000,000.0 |  |  |  |  |  |
Accident Year 2022 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 170,900,000 | 173,200,000 | 166,000,000.0 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 13,500,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 5,801 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 143,400,000 | 113,200,000 | 41,000,000.0 |  |  |  |  |  |  |
Accident Year 2022 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 208,700,000 | 212,900,000 | 202,400,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 119,400,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,594 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 46,400,000 | 26,600,000 | 8,900,000 |  |  |  |  |  |  |
Accident Year 2022 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 112,700,000 | 105,300,000 | 107,200,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 25,700,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 5,410 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 73,500,000 | 57,500,000 | 24,900,000 |  |  |  |  |  |  |
Accident Year 2022 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 268,600,000 | 299,800,000 | 314,100,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 121,300,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 3,356 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 113,400,000 | 75,100,000 | 17,700,000 |  |  |  |  |  |  |
Accident Year 2022 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 372,100,000 | 378,900,000 | 380,500,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 43,600,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,475 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 261,300,000 | 193,600,000 | 63,300,000 |  |  |  |  |  |  |
Accident Year 2022 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 246,000,000.0 | 247,800,000 | 246,600,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 138,500,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,650 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 59,600,000 | 30,700,000 | 9,100,000 |  |  |  |  |  |  |
Accident Year 2022 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 196,200,000 | 191,600,000 | 192,600,000 |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 98,900,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,458 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 74,300,000 | 52,600,000 | $ 25,300,000 |  |  |  |  |  |  |
Accident Year 2023 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 130,100,000 | 150,800,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 44,300,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 4,056 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 65,200,000 | 29,800,000 |  |  |  |  |  |  |  |
Accident Year 2023 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 233,800,000 | 223,100,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 156,000,000.0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 3,105 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 3,300,000 | 5,500,000 |  |  |  |  |  |  |  |
Accident Year 2023 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 110,300,000 | 116,600,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 20,800,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 3,997 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 73,200,000 | 27,800,000 |  |  |  |  |  |  |  |
Accident Year 2023 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 347,600,000 | 338,500,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 169,100,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 3,385 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 100,600,000 | 21,300,000 |  |  |  |  |  |  |  |
Accident Year 2023 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 215,000,000.0 | 223,600,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 40,400,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,104 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 103,800,000 | 43,900,000 |  |  |  |  |  |  |  |
Accident Year 2023 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 267,700,000 | 268,300,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 187,600,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,565 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 35,000,000.0 | 8,200,000 |  |  |  |  |  |  |  |
Accident Year 2023 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 144,300,000 | 140,700,000 |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 73,000,000.0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 1,188 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 48,100,000 | $ 22,300,000 |  |  |  |  |  |  |  |
Accident Year 2024 | Property Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 132,600,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 84,200,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 1,879 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 19,100,000 |  |  |  |  |  |  |  |  |
Accident Year 2024 | Casualty Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 235,600,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 203,200,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 1,782 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 36,000,000.0 |  |  |  |  |  |  |  |  |
Accident Year 2024 | Marine, Aviation and Energy Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 109,600,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 62,300,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 2,358 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 32,400,000 |  |  |  |  |  |  |  |  |
Accident Year 2024 | Financial and Professional Insurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 423,200,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 292,300,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | 3,756 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 89,200,000 |  |  |  |  |  |  |  |  |
Accident Year 2024 | Property Catastrophe and Other Property Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 254,500,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 135,500,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 737 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 32,800,000 |  |  |  |  |  |  |  |  |
Accident Year 2024 | Casualty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 286,900,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 260,000,000.0 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 848 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 9,400,000 |  |  |  |  |  |  |  |  |
Accident Year 2024 | Specialty Reinsurance |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 153,500,000 |  |  |  |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 125,600,000 |  |  |  |  |  |  |  |  |
Number of Reported Claims | Integer | 803 |  |  |  |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, Net | $ 14,000,000.0 |  |  |  |  |  |  |  |  |

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