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Reserves For Losses And Loss Expenses (Loss and Loss Expenses Incurred, Net of Reinsurance, and Cumulative Paid Claims and Claim Adjustment Expenses, Net of Reinsurance) (Details) $ in Thousands | Dec. 31, 2022 USD ($) claim | Dec. 31, 2021 USD ($) | 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] |  |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses, net of reinsurance | $ 14,665,237 |  |  |  |  |  |  |  |  |
Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 11,924,316 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 6,513,546 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses before 2013, net of reinsurance | 125,357 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses, net of reinsurance | 5,536,127 |  |  |  |  |  |  |  |  |
Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 6,716,685 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 5,008,947 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses before 2013, net of reinsurance | 214,233 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses, net of reinsurance | 1,921,971 |  |  |  |  |  |  |  |  |
Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 3,874,102 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 2,161,200 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses before 2013, net of reinsurance | 36,484 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses, net of reinsurance | 1,749,386 |  |  |  |  |  |  |  |  |
Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 4,968,723 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 3,819,737 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses before 2013, net of reinsurance | 3,731 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses, net of reinsurance | 1,152,717 |  |  |  |  |  |  |  |  |
Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 7,538,091 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 6,781,190 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses before 2013, net of reinsurance | 4,727 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses, net of reinsurance | 761,628 |  |  |  |  |  |  |  |  |
Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 3,147,324 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 1,572,474 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses before 2013, net of reinsurance | 417,861 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses, net of reinsurance | 1,992,711 |  |  |  |  |  |  |  |  |
Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 612,376 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 110,777 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses before 2013, net of reinsurance | 644,712 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses, net of reinsurance | 1,146,311 |  |  |  |  |  |  |  |  |
Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 1,325,878 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 1,047,114 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses before 2013, net of reinsurance | 1,036 |  |  |  |  |  |  |  |  |
Reserves for loss and loss adjustment expenses, net of reinsurance | 279,800 |  |  |  |  |  |  |  |  |
Accident Year 2011 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 809,358 | $ 807,998 | $ 805,915 | $ 801,689 | $ 806,914 | $ 800,593 | $ 779,706 | $ 779,908 | $ 788,581 | $ 749,261
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 761,461 | 738,858 | 717,908 | 691,495 | 646,257 | 585,608 | 470,566 | 330,127 | 188,023 | 63,243
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 21,362 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 26,000 |  |  |  |  |  |  |  |  |
Accident Year 2011 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 534,948 | 538,503 | 540,322 | 541,926 | 542,274 | 547,000 | 543,238 | 546,995 | 547,295 | 552,570
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 502,181 | 496,809 | 489,075 | 479,104 | 466,580 | 447,894 | 414,160 | 363,028 | 277,538 | 117,900
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 11,473 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 53,000 |  |  |  |  |  |  |  |  |
Accident Year 2011 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 283,216 | 279,870 | 279,824 | 281,888 | 276,566 | 267,978 | 246,943 | 241,046 | 244,556 | 265,061
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 273,094 | 267,776 | 261,106 | 255,863 | 246,616 | 204,955 | 176,079 | 118,767 | 63,503 | 23,295
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 4,681 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 7,000 |  |  |  |  |  |  |  |  |
Accident Year 2011 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 364,607 | 364,439 | 364,207 | 365,275 | 366,166 | 366,646 | 376,243 | 368,894 | 349,136 | 327,514
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 364,147 | 362,624 | 362,252 | 361,499 | 352,792 | 342,961 | 321,855 | 267,253 | 218,596 | 142,929
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 103 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 44,000 |  |  |  |  |  |  |  |  |
Accident Year 2011 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 541,728 | 541,857 | 542,148 | 542,863 | 544,681 | 548,169 | 549,518 | 565,810 | 573,905 | 565,391
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 539,081 | 538,985 | 537,582 | 536,416 | 535,756 | 534,569 | 527,789 | 526,031 | 480,140 | 310,750
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 1,125 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 25,000 |  |  |  |  |  |  |  |  |
Accident Year 2011 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 302,135 | 302,672 | 301,415 | 302,595 | 298,317 | 291,105 | 282,307 | 272,475 | 269,340 | 318,365
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 263,467 | 254,273 | 241,573 | 225,882 | 205,553 | 178,060 | 144,331 | 108,852 | 63,745 | 28,945
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 12,543 |  |  |  |  |  |  |  |  |
Accident Year 2011 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 23,306 | 25,701 | 29,758 | 31,752 | 35,120 | 40,207 | 44,162 | 48,143 | 50,355 | 63,995
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 9,490 | 8,805 | 6,476 | 5,349 | 4,418 | 3,396 | 3,008 | 3,588 | 1,897 | 647
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 5,184 |  |  |  |  |  |  |  |  |
Accident Year 2011 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 105,711 | 106,316 | 107,552 | 109,697 | 111,890 | 112,572 | 111,937 | 114,100 | 112,616 | 141,380
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 105,059 | 104,388 | 104,403 | 107,603 | 106,043 | 104,323 | 101,538 | 92,625 | 74,572 | $ 36,577
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 72 |  |  |  |  |  |  |  |  |
Accident Year 2012 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 862,630 | 861,382 | 862,749 | 867,400 | 861,313 | 848,138 | 843,501 | 845,564 | 844,832 |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 781,533 | 758,098 | 728,718 | 678,490 | 592,828 | 478,924 | 337,426 | 190,419 | 78,705 |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 35,808 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 28,000 |  |  |  |  |  |  |  |  |
Accident Year 2012 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 598,977 | 602,000 | 600,194 | 604,030 | 615,435 | 617,242 | 627,767 | 637,307 | 639,436 |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 547,894 | 538,914 | 531,475 | 521,141 | 503,915 | 471,235 | 412,611 | 319,743 | 148,405 |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 21,528 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 57,000 |  |  |  |  |  |  |  |  |
Accident Year 2012 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 253,244 | 254,243 | 254,868 | 255,850 | 236,961 | 241,376 | 257,309 | 244,574 | 250,740 |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 237,145 | 234,459 | 225,236 | 213,888 | 197,272 | 174,524 | 137,341 | 83,063 | 19,225 |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 12,284 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 7,000 |  |  |  |  |  |  |  |  |
Accident Year 2012 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 407,970 | 406,589 | 407,470 | 411,920 | 412,120 | 414,732 | 416,802 | 385,241 | 363,891 |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 405,004 | 404,259 | 403,273 | 400,577 | 392,658 | 364,054 | 326,854 | 237,648 | 155,564 |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 403 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 47,000 |  |  |  |  |  |  |  |  |
Accident Year 2012 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 658,557 | 660,250 | 662,012 | 659,568 | 659,230 | 658,252 | 659,563 | 697,845 | 691,971 |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 654,089 | 653,784 | 653,272 | 650,816 | 643,619 | 628,440 | 609,948 | 587,607 | 368,865 |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 1,549 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 30,000 |  |  |  |  |  |  |  |  |
Accident Year 2012 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 341,649 | 336,990 | 335,883 | 324,150 | 324,693 | 330,382 | 318,443 | 318,904 | 319,454 |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 284,360 | 271,512 | 252,155 | 227,448 | 197,996 | 155,070 | 115,779 | 68,374 | 21,297 |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 16,184 |  |  |  |  |  |  |  |  |
Accident Year 2012 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 35,707 | 40,652 | 42,618 | 42,541 | 41,671 | 45,823 | 49,570 | 57,650 | 63,561 |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 13,491 | 11,938 | 11,154 | 7,595 | 5,808 | 4,175 | 3,354 | 2,341 | 377 |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 7,484 |  |  |  |  |  |  |  |  |
Accident Year 2012 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 96,656 | 97,315 | 99,244 | 98,838 | 99,176 | 99,941 | 97,195 | 96,492 | 112,907 |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 95,633 | 95,198 | 94,565 | 93,099 | 91,390 | 88,257 | 82,119 | 66,829 | $ 38,780 |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 177 |  |  |  |  |  |  |  |  |
Accident Year 2013 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 1,010,796 | 981,071 | 974,345 | 964,301 | 961,761 | 958,734 | 984,262 | 948,389 |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 872,657 | 814,191 | 755,641 | 674,665 | 536,855 | 381,328 | 210,151 | 82,638 |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 55,430 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 27,000 |  |  |  |  |  |  |  |  |
Accident Year 2013 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 612,687 | 617,478 | 620,741 | 626,432 | 641,169 | 650,997 | 690,525 | 712,800 |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 557,215 | 544,849 | 531,512 | 512,933 | 477,541 | 421,734 | 323,744 | 139,320 |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 29,213 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 58,000 |  |  |  |  |  |  |  |  |
Accident Year 2013 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 286,271 | 282,065 | 281,718 | 290,141 | 274,546 | 272,899 | 256,595 | 257,946 |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 246,031 | 239,150 | 232,143 | 215,408 | 186,688 | 139,205 | 85,047 | 20,331 |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 19,949 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 8,000 |  |  |  |  |  |  |  |  |
Accident Year 2013 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 427,923 | 426,107 | 428,981 | 430,557 | 429,608 | 421,522 | 415,446 | 389,577 |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 418,993 | 415,170 | 409,426 | 396,018 | 368,448 | 323,429 | 263,663 | 159,987 |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 1,362 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 53,000 |  |  |  |  |  |  |  |  |
Accident Year 2013 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 710,978 | 710,663 | 712,361 | 713,899 | 721,789 | 723,206 | 726,287 | 736,523 |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 708,214 | 708,065 | 701,341 | 695,563 | 686,029 | 664,084 | 608,748 | 392,921 |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 3,842 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 32,000 |  |  |  |  |  |  |  |  |
Accident Year 2013 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 309,317 | 304,805 | 303,261 | 293,094 | 252,277 | 230,085 | 231,430 | 259,019 |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 250,880 | 233,643 | 205,289 | 178,521 | 141,254 | 91,140 | 48,442 | 17,888 |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 19,728 |  |  |  |  |  |  |  |  |
Accident Year 2013 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 30,104 | 36,774 | 39,781 | 39,682 | 45,115 | 50,099 | 57,897 | 69,977 |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 6,457 | 5,421 | 5,083 | 4,416 | 4,099 | 3,272 | 2,481 | 2,069 |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 8,683 |  |  |  |  |  |  |  |  |
Accident Year 2013 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 131,342 | 130,642 | 131,071 | 129,398 | 130,301 | 131,625 | 117,452 | 127,118 |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 127,995 | 126,848 | 125,439 | 122,566 | 118,552 | 109,051 | 89,121 | $ 53,474 |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 1,061 |  |  |  |  |  |  |  |  |
Accident Year 2014 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 1,091,569 | 1,059,897 | 1,043,948 | 1,029,821 | 1,018,253 | 1,009,051 | 1,016,106 |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 870,981 | 766,515 | 676,735 | 557,998 | 389,862 | 208,828 | 69,407 |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 96,310 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 28,000 |  |  |  |  |  |  |  |  |
Accident Year 2014 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 654,385 | 657,972 | 651,278 | 660,520 | 684,700 | 696,339 | 702,716 |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 572,669 | 558,934 | 537,861 | 504,850 | 446,072 | 338,835 | 142,998 |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 36,834 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 58,000 |  |  |  |  |  |  |  |  |
Accident Year 2014 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 463,102 | 467,545 | 438,065 | 400,799 | 360,110 | 323,222 | 309,417 |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 404,742 | 356,812 | 296,863 | 254,872 | 201,019 | 102,173 | 28,517 |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 33,241 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 9,000 |  |  |  |  |  |  |  |  |
Accident Year 2014 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 439,682 | 437,884 | 438,192 | 441,408 | 440,334 | 429,074 | 429,329 |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 426,955 | 418,499 | 407,989 | 388,554 | 339,657 | 277,665 | 183,160 |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 2,244 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 52,000 |  |  |  |  |  |  |  |  |
Accident Year 2014 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 752,604 | 753,952 | 751,530 | 757,009 | 762,460 | 775,308 | 771,390 |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 739,244 | 738,390 | 731,651 | 726,549 | 711,385 | 669,891 | 416,611 |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 3,363 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 34,000 |  |  |  |  |  |  |  |  |
Accident Year 2014 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 310,451 | 301,355 | 301,663 | 267,850 | 245,268 | 252,638 | 240,655 |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 225,077 | 205,354 | 171,719 | 140,299 | 100,200 | 61,770 | 19,904 |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 24,928 |  |  |  |  |  |  |  |  |
Accident Year 2014 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 61,432 | 65,222 | 65,485 | 64,957 | 71,404 | 70,281 | 72,657 |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 11,819 | 9,883 | 7,685 | 5,928 | 5,573 | 4,783 | 2,498 |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 13,634 |  |  |  |  |  |  |  |  |
Accident Year 2014 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 185,249 | 184,150 | 186,159 | 180,885 | 181,634 | 174,423 | 167,901 |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 182,411 | 178,060 | 175,949 | 168,506 | 157,404 | 133,516 | $ 78,920 |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 1,482 |  |  |  |  |  |  |  |  |
Accident Year 2015 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 1,249,129 | 1,178,604 | 1,138,785 | 1,121,833 | 1,099,396 | 1,065,550 |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 930,630 | 774,738 | 638,934 | 453,097 | 255,603 | 79,887 |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 142,974 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 28,000 |  |  |  |  |  |  |  |  |
Accident Year 2015 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 682,153 | 683,880 | 673,216 | 689,622 | 733,505 | 762,093 |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 583,258 | 559,198 | 525,753 | 468,817 | 362,299 | 153,456 |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 41,944 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 58,000 |  |  |  |  |  |  |  |  |
Accident Year 2015 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 393,409 | 384,416 | 377,410 | 338,723 | 332,400 | 333,267 |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 306,713 | 261,225 | 243,088 | 162,829 | 96,312 | 36,503 |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 53,786 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 10,000 |  |  |  |  |  |  |  |  |
Accident Year 2015 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 444,472 | 439,991 | 434,170 | 430,198 | 428,419 | 430,440 |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 419,545 | 401,844 | 371,761 | 326,861 | 267,326 | 180,545 |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 4,800 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 47,000 |  |  |  |  |  |  |  |  |
Accident Year 2015 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 747,869 | 746,603 | 747,003 | 747,630 | 753,326 | 752,727 |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 741,685 | 734,509 | 730,688 | 718,538 | 689,662 | 445,285 |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 8,195 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 42,000 |  |  |  |  |  |  |  |  |
Accident Year 2015 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 298,486 | 281,254 | 261,482 | 238,883 | 220,699 | 231,082 |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 175,059 | 147,311 | 123,614 | 69,350 | 40,085 | 16,469 |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 36,491 |  |  |  |  |  |  |  |  |
Accident Year 2015 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 62,647 | 66,795 | 71,025 | 70,749 | 80,508 | 76,701 |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 19,275 | 18,375 | 17,327 | 15,356 | 12,810 | 6,282 |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 16,529 |  |  |  |  |  |  |  |  |
Accident Year 2015 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 192,379 | 191,867 | 197,978 | 199,410 | 200,394 | 206,560 |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 185,823 | 182,609 | 179,749 | 171,675 | 141,340 | $ 72,126 |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 1,209 |  |  |  |  |  |  |  |  |
Accident Year 2016 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 1,232,803 | 1,156,157 | 1,121,317 | 1,131,549 | 1,103,900 |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 806,869 | 615,753 | 435,729 | 264,299 | 86,798 |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 181,880 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 27,000 |  |  |  |  |  |  |  |  |
Accident Year 2016 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 721,170 | 724,056 | 715,055 | 724,697 | 778,964 |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 613,675 | 574,889 | 508,546 | 397,464 | 171,006 |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 43,766 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 56,000 |  |  |  |  |  |  |  |  |
Accident Year 2016 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 382,409 | 359,566 | 333,408 | 322,176 | 334,848 |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 244,284 | 198,697 | 155,212 | 99,598 | 28,101 |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 73,828 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 10,000 |  |  |  |  |  |  |  |  |
Accident Year 2016 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 521,667 | 494,315 | 478,966 | 462,544 | 442,610 |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 463,117 | 412,874 | 350,110 | 281,475 | 180,056 |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 10,720 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 46,000 |  |  |  |  |  |  |  |  |
Accident Year 2016 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 742,289 | 744,544 | 746,265 | 748,931 | 759,634 |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 725,228 | 725,138 | 708,214 | 661,741 | 414,910 |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 11,491 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 48,000 |  |  |  |  |  |  |  |  |
Accident Year 2016 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 261,148 | 246,898 | 230,790 | 210,397 | 221,193 |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 141,553 | 109,474 | 77,498 | 40,953 | 11,076 |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 44,474 |  |  |  |  |  |  |  |  |
Accident Year 2016 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 57,847 | 66,180 | 71,448 | 72,505 | 77,820 |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 12,414 | 10,359 | 9,368 | 8,230 | 6,141 |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 20,826 |  |  |  |  |  |  |  |  |
Accident Year 2016 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 102,953 | 105,101 | 103,104 | 112,068 | 108,220 |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 94,870 | 87,736 | 82,259 | 65,079 | $ 33,991 |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 1,754 |  |  |  |  |  |  |  |  |
Accident Year 2017 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 1,294,681 | 1,237,824 | 1,237,336 | 1,240,560 |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 704,928 | 471,239 | 275,343 | 88,195 |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 292,625 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 28,000 |  |  |  |  |  |  |  |  |
Accident Year 2017 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 734,034 | 732,762 | 721,018 | 784,281 |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 581,003 | 515,914 | 397,376 | 184,715 |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 67,254 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 54,000 |  |  |  |  |  |  |  |  |
Accident Year 2017 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 354,283 | 345,614 | 332,385 | 336,129 |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 200,521 | 147,985 | 97,466 | 31,674 |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 93,387 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 11,000 |  |  |  |  |  |  |  |  |
Accident Year 2017 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 530,876 | 504,813 | 488,291 | 483,019 |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 440,378 | 374,479 | 290,124 | 185,236 |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 22,483 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 45,000 |  |  |  |  |  |  |  |  |
Accident Year 2017 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 684,708 | 691,015 | 701,241 | 721,073 |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 657,819 | 645,374 | 615,869 | 404,975 |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 18,311 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 43,000 |  |  |  |  |  |  |  |  |
Accident Year 2017 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 240,848 | 239,131 | 230,460 | 236,318 |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 94,856 | 64,020 | 39,091 | 14,560 |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 72,504 |  |  |  |  |  |  |  |  |
Accident Year 2017 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 73,978 | 76,242 | 77,482 | 78,929 |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 15,436 | 12,728 | 10,884 | 6,241 |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 21,878 |  |  |  |  |  |  |  |  |
Accident Year 2017 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 81,014 | 81,858 | 77,062 | 103,113 |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 71,054 | 68,457 | 54,499 | $ 23,081 |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 3,637 |  |  |  |  |  |  |  |  |
Accident Year 2018 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 1,158,880 | 1,212,790 | 1,339,565 |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 423,283 | 225,068 | 72,232 |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 489,718 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 22,000 |  |  |  |  |  |  |  |  |
Accident Year 2018 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 704,008 | 716,430 | 725,245 |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 485,203 | 380,454 | 172,478 |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 96,322 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 42,000 |  |  |  |  |  |  |  |  |
Accident Year 2018 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 337,961 | 375,577 | 394,107 |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 129,168 | 80,408 | 28,106 |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 159,767 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 11,000 |  |  |  |  |  |  |  |  |
Accident Year 2018 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 442,163 | 428,759 | 523,736 |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 308,451 | 228,357 | 142,815 |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 31,172 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 30,000 |  |  |  |  |  |  |  |  |
Accident Year 2018 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 922,333 | 904,580 | 900,683 |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 845,714 | 784,670 | 460,434 |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 24,934 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 38,000 |  |  |  |  |  |  |  |  |
Accident Year 2018 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 289,878 | 293,345 | 299,602 |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 81,789 | 49,664 | 20,750 |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 136,865 |  |  |  |  |  |  |  |  |
Accident Year 2018 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 80,452 | 83,468 | 84,354 |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 10,471 | 8,699 | 4,869 |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 35,638 |  |  |  |  |  |  |  |  |
Accident Year 2018 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 116,774 | 117,867 | 114,590 |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 86,888 | 65,575 | $ 26,574 |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 3,946 |  |  |  |  |  |  |  |  |
Accident Year 2019 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 1,390,790 | 1,534,580 |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 267,685 | 76,612 |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 841,854 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 23,000 |  |  |  |  |  |  |  |  |
Accident Year 2019 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 701,703 | 742,687 |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 384,867 | 172,729 |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 149,447 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 45,000 |  |  |  |  |  |  |  |  |
Accident Year 2019 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 471,266 | 524,879 |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 86,056 | 28,586 |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 315,877 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 11,000 |  |  |  |  |  |  |  |  |
Accident Year 2019 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 596,810 | 614,422 |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 319,941 | 180,860 |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 111,412 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 38,000 |  |  |  |  |  |  |  |  |
Accident Year 2019 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 832,183 | 828,187 |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 698,092 | 405,512 |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 57,246 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 36,000 |  |  |  |  |  |  |  |  |
Accident Year 2019 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 346,736 | 359,952 |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 43,838 | 10,918 |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 243,222 |  |  |  |  |  |  |  |  |
Accident Year 2019 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 87,980 | 98,110 |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 6,026 | 4,586 |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 48,670 |  |  |  |  |  |  |  |  |
Accident Year 2019 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 146,761 | 133,938 |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 71,797 | $ 15,235 |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 28,634 |  |  |  |  |  |  |  |  |
Accident Year 2020 | Other liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 1,823,680 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 93,519 |  |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 1,507,284 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 20,000 |  |  |  |  |  |  |  |  |
Accident Year 2020 | Workers' compensation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 772,620 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 180,982 |  |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 348,348 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 41,000 |  |  |  |  |  |  |  |  |
Accident Year 2020 | Professional liability |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 648,941 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 33,446 |  |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 543,483 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 10,000 |  |  |  |  |  |  |  |  |
Accident Year 2020 | Commercial automobile |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 792,553 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 253,206 |  |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 342,905 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 40,000 |  |  |  |  |  |  |  |  |
Accident Year 2020 | Short-tail lines |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 944,842 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 472,024 |  |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 235,121 |  |  |  |  |  |  |  |  |
Short-duration insurance contract, cumulative number of reported claims | claim | 32,000 |  |  |  |  |  |  |  |  |
Accident Year 2020 | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | $ 446,676 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 11,595 |  |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 402,204 |  |  |  |  |  |  |  |  |
Accident Year 2020 | Monoline excess |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 98,923 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 5,898 |  |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | 66,865 |  |  |  |  |  |  |  |  |
Accident Year 2020 | Property |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Loss and loss expenses incurred, net of reinsurance | 167,039 |  |  |  |  |  |  |  |  |
Cumulative paid claims and claim adjustment expenses, net of reinsurance | 25,584 |  |  |  |  |  |  |  |  |
Short-duration insurance contracts, incurred but not reported (IBNR) claims liability, net | $ 78,818 |  |  |  |  |  |  |  |  |

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