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RESERVE FOR LOSSES AND LOSS EXPENSES - Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Details)
$ in Thousands
Dec. 31, 2023
USD ($)
claim
Dec. 31, 2022
USD ($)
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 ($)
Dec. 31, 2014
USD ($)
Insurance | Property                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 4,108,843                  
Insurance | Property | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 253,414 $ 253,203 $ 253,279 $ 255,887 $ 259,792 $ 262,173 $ 262,701 $ 277,183 $ 287,431 $ 289,270
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 775                  
Cumulative number of reported claims | claim 4,174                  
Insurance | Property | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 181,928 181,323 179,075 189,066 186,952 190,310 192,736 200,398 207,711  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 85                  
Cumulative number of reported claims | claim 4,194                  
Insurance | Property | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 264,976 259,786 260,370 259,319 265,152 279,532 287,858 263,762    
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 1,951                  
Cumulative number of reported claims | claim 6,668                  
Insurance | Property | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 669,951 675,409 675,085 679,243 688,755 700,638 794,042      
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 6,375                  
Cumulative number of reported claims | claim 10,096                  
Insurance | Property | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 600,596 609,977 611,057 618,888 639,465 608,422        
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 12,492                  
Cumulative number of reported claims | claim 9,659                  
Insurance | Property | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 353,671 369,962 359,092 364,350 374,678          
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 4,503                  
Cumulative number of reported claims | claim 9,561                  
Insurance | Property | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 593,780 584,921 635,344 654,495            
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 24,336                  
Cumulative number of reported claims | claim 12,417                  
Insurance | Property | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 372,223 375,607 378,554              
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 9,213                  
Cumulative number of reported claims | claim 7,730                  
Insurance | Property | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 419,139 414,743                
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 49,138                  
Cumulative number of reported claims | claim 7,410                  
Insurance | Property | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 399,165                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 188,657                  
Cumulative number of reported claims | claim 5,732                  
Insurance | Accident and health                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 931,062                  
Insurance | Accident and health | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 64,392 62,703 64,070 64,938 65,710 64,973 65,347 66,874 67,380 71,520
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 1,621                  
Cumulative number of reported claims | claim 58,081                  
Insurance | Accident and health | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 61,759 64,433 63,772 64,441 64,771 64,219 66,013 69,494 70,622  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 1,049                  
Cumulative number of reported claims | claim 44,138                  
Insurance | Accident and health | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 87,399 87,972 88,180 87,154 87,470 86,338 85,892 85,244    
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 2,179                  
Cumulative number of reported claims | claim 87,001                  
Insurance | Accident and health | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 118,125 117,012 117,131 117,050 118,949 121,146 113,921      
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 36                  
Cumulative number of reported claims | claim 688,000                  
Insurance | Accident and health | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 114,844 114,134 113,118 115,077 115,977 111,119        
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 291                  
Cumulative number of reported claims | claim 745,012                  
Insurance | Accident and health | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 68,344 69,203 65,623 75,093 73,926          
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 121                  
Cumulative number of reported claims | claim 675,634                  
Insurance | Accident and health | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 64,297 67,525 63,963 69,679            
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 1,275                  
Cumulative number of reported claims | claim 718,512                  
Insurance | Accident and health | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 78,478 72,044 69,543              
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 3,605                  
Cumulative number of reported claims | claim 433,643                  
Insurance | Accident and health | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 100,629 98,796                
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 9,807                  
Cumulative number of reported claims | claim 380,675                  
Insurance | Accident and health | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 172,795                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 67,393                  
Cumulative number of reported claims | claim 222,537                  
Insurance | Marine and aviation                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 1,894,826                  
Insurance | Marine and aviation | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 52,308 52,286 53,013 55,526 63,693 65,913 64,768 71,051 66,878 80,064
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 830                  
Cumulative number of reported claims | claim 3,566                  
Insurance | Marine and aviation | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 143,900 145,394 145,447 146,174 140,673 153,737 161,465 165,908 187,067  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 111                  
Cumulative number of reported claims | claim 4,312                  
Insurance | Marine and aviation | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 102,345 101,388 100,488 101,351 101,928 109,478 111,878 115,520    
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 2,038                  
Cumulative number of reported claims | claim 4,836                  
Insurance | Marine and aviation | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 215,683 217,232 217,443 225,397 227,355 229,801 262,628      
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 6,867                  
Cumulative number of reported claims | claim 8,577                  
Insurance | Marine and aviation | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 229,903 228,369 234,901 241,715 255,652 238,117        
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 14,910                  
Cumulative number of reported claims | claim 8,742                  
Insurance | Marine and aviation | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 224,914 226,586 213,480 210,536 215,911          
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 14,884                  
Cumulative number of reported claims | claim 7,697                  
Insurance | Marine and aviation | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 164,808 163,700 180,156 208,542            
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 14,618                  
Cumulative number of reported claims | claim 6,439                  
Insurance | Marine and aviation | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 204,483 221,864 240,182              
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 34,829                  
Cumulative number of reported claims | claim 6,754                  
Insurance | Marine and aviation | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 257,637 265,181                
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 92,387                  
Cumulative number of reported claims | claim 7,159                  
Insurance | Marine and aviation | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 298,845                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 210,136                  
Cumulative number of reported claims | claim 5,172                  
Insurance | Cyber                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 740,868                  
Insurance | Cyber | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 40,743 39,832 43,576 39,516 42,887 47,342 57,876 69,955 69,690 70,557
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 604                  
Cumulative number of reported claims | claim 1,159                  
Insurance | Cyber | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 48,042 49,795 52,526 50,758 50,357 51,250 63,066 63,595 65,231  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 2,046                  
Cumulative number of reported claims | claim 1,427                  
Insurance | Cyber | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 25,258 27,873 29,929 37,322 40,266 58,261 56,565 58,741    
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 1,072                  
Cumulative number of reported claims | claim 1,667                  
Insurance | Cyber | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 48,333 48,685 50,905 51,931 56,783 50,794 53,187      
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 3,234                  
Cumulative number of reported claims | claim 1,817                  
Insurance | Cyber | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 24,495 26,732 31,111 33,962 31,966 33,429        
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 4,574                  
Cumulative number of reported claims | claim 2,152                  
Insurance | Cyber | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 73,152 82,006 81,982 58,717 54,444          
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 14,109                  
Cumulative number of reported claims | claim 2,900                  
Insurance | Cyber | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 126,457 103,175 106,333 114,209            
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 25,132                  
Cumulative number of reported claims | claim 2,856                  
Insurance | Cyber | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 105,642 134,382 125,460              
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 20,662                  
Cumulative number of reported claims | claim 2,432                  
Insurance | Cyber | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 120,494 129,361                
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 71,510                  
Cumulative number of reported claims | claim 1,730                  
Insurance | Cyber | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 128,252                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 102,582                  
Cumulative number of reported claims | claim 1,503                  
Insurance | Professional lines                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 3,778,367                  
Insurance | Professional lines | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 305,060 301,289 304,657 305,201 308,193 321,027 331,044 348,064 338,670 338,378
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 35,601                  
Cumulative number of reported claims | claim 8,881                  
Insurance | Professional lines | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 282,238 283,894 272,909 274,091 291,176 304,062 317,455 310,926 309,864  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 20,475                  
Cumulative number of reported claims | claim 9,341                  
Insurance | Professional lines | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 356,814 340,465 339,513 329,270 316,592 297,852 293,399 288,595    
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 32,954                  
Cumulative number of reported claims | claim 10,590                  
Insurance | Professional lines | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 396,732 392,002 394,154 376,993 376,569 343,055 339,231      
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 53,138                  
Cumulative number of reported claims | claim 12,605                  
Insurance | Professional lines | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 468,504 449,212 423,162 392,819 342,931 325,926        
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 76,008                  
Cumulative number of reported claims | claim 15,333                  
Insurance | Professional lines | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 460,120 412,150 378,899 363,998 347,810          
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 83,773                  
Cumulative number of reported claims | claim 14,606                  
Insurance | Professional lines | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 293,935 302,097 321,530 322,386            
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 130,739                  
Cumulative number of reported claims | claim 9,318                  
Insurance | Professional lines | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 326,128 369,587 378,660              
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 198,067                  
Cumulative number of reported claims | claim 8,127                  
Insurance | Professional lines | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 447,359 461,196                
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 371,912                  
Cumulative number of reported claims | claim 8,041                  
Insurance | Professional lines | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 441,477                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 414,023                  
Cumulative number of reported claims | claim 7,251                  
Insurance | Credit and political risk                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 403,080                  
Insurance | Credit and political risk | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 69,677 69,677 69,113 70,748 71,274 69,589 68,323 67,109 70,712 38,825
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 0                  
Cumulative number of reported claims | claim 6                  
Insurance | Credit and political risk | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 23,309 23,309 24,189 24,851 25,930 26,012 27,524 30,368 30,329  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 0                  
Cumulative number of reported claims | claim 2                  
Insurance | Credit and political risk | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 24,885 24,885 25,965 26,946 43,160 42,589 45,079 45,006    
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 0                  
Cumulative number of reported claims | claim 2                  
Insurance | Credit and political risk | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 8,566 11,068 16,022 18,269 26,044 32,808 48,181      
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 2,086                  
Cumulative number of reported claims | claim 4                  
Insurance | Credit and political risk | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 24,356 21,182 24,845 32,738 33,747 42,976        
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 5,584                  
Cumulative number of reported claims | claim 2                  
Insurance | Credit and political risk | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 71,270 74,066 75,610 81,470 53,332          
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 11,546                  
Cumulative number of reported claims | claim 31                  
Insurance | Credit and political risk | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 50,987 62,235 70,428 61,928            
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 19,594                  
Cumulative number of reported claims | claim 43                  
Insurance | Credit and political risk | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 26,322 37,104 42,417              
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 13,363                  
Cumulative number of reported claims | claim 23                  
Insurance | Credit and political risk | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 44,450 45,444                
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 37,463                  
Cumulative number of reported claims | claim 24                  
Insurance | Credit and political risk | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 59,258                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 54,333                  
Cumulative number of reported claims | claim 19                  
Insurance | Liability                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 2,522,710                  
Insurance | Liability | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 131,210 132,474 132,043 132,565 131,469 132,013 130,666 129,750 124,289 107,126
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 9,697                  
Cumulative number of reported claims | claim 5,820                  
Insurance | Liability | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 189,795 188,261 186,931 188,004 182,690 164,982 137,477 127,299 128,436  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 18,423                  
Cumulative number of reported claims | claim 6,769                  
Insurance | Liability | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 124,969 125,614 120,187 120,199 127,451 128,854 130,160 124,313    
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 17,081                  
Cumulative number of reported claims | claim 7,648                  
Insurance | Liability | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 250,887 214,707 204,533 200,391 184,781 166,052 167,334      
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 37,518                  
Cumulative number of reported claims | claim 8,812                  
Insurance | Liability | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 251,875 216,038 204,519 190,639 167,672 167,552        
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 38,901                  
Cumulative number of reported claims | claim 8,644                  
Insurance | Liability | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 300,584 238,035 222,885 193,435 192,468          
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 66,863                  
Cumulative number of reported claims | claim 8,183                  
Insurance | Liability | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 249,189 230,921 225,038 224,616            
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 88,543                  
Cumulative number of reported claims | claim 6,180                  
Insurance | Liability | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 302,023 245,585 232,051              
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 141,022                  
Cumulative number of reported claims | claim 6,748                  
Insurance | Liability | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 357,574 323,261                
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 246,679                  
Cumulative number of reported claims | claim 7,365                  
Insurance | Liability | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 364,604                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 331,464                  
Cumulative number of reported claims | claim 5,168                  
Reinsurance | Accident and health                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses $ 1,881,315                  
Reinsurance | Accident and health | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 87,664 87,978 88,095 87,806 86,846 86,843 86,833 89,303 102,403 101,409
Total of incurred-but-not-reported liabilities plus expected development on reported claims 125                  
Reinsurance | Accident and health | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 93,133 92,388 92,431 93,422 93,081 93,807 94,047 100,522 93,831  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 105                  
Reinsurance | Accident and health | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 190,662 190,534 190,574 189,538 190,067 188,454 191,299 170,687    
Total of incurred-but-not-reported liabilities plus expected development on reported claims 16                  
Reinsurance | Accident and health | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 182,479 183,484 183,513 182,477 183,574 189,610 183,937      
Total of incurred-but-not-reported liabilities plus expected development on reported claims (16)                  
Reinsurance | Accident and health | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 197,493 200,467 201,133 198,365 200,576 193,749        
Total of incurred-but-not-reported liabilities plus expected development on reported claims 766                  
Reinsurance | Accident and health | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 199,419 205,403 207,794 212,307 217,477          
Total of incurred-but-not-reported liabilities plus expected development on reported claims 1,328                  
Reinsurance | Accident and health | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 199,958 213,960 220,969 226,883            
Total of incurred-but-not-reported liabilities plus expected development on reported claims 1,757                  
Reinsurance | Accident and health | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 222,718 227,326 232,091              
Total of incurred-but-not-reported liabilities plus expected development on reported claims 9,765                  
Reinsurance | Accident and health | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 264,615 267,525                
Total of incurred-but-not-reported liabilities plus expected development on reported claims 40,396                  
Reinsurance | Accident and health | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 243,174                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 91,280                  
Reinsurance | Marine and aviation                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 405,166                  
Reinsurance | Marine and aviation | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 9,841 9,530 9,025 8,786 8,535 9,192 7,209 8,019 9,162 10,192
Total of incurred-but-not-reported liabilities plus expected development on reported claims 368                  
Reinsurance | Marine and aviation | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 12,054 11,998 12,046 12,281 12,652 15,019 10,836 9,242 10,366  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 527                  
Reinsurance | Marine and aviation | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 36,263 36,773 36,371 36,052 37,519 36,130 35,965 32,453    
Total of incurred-but-not-reported liabilities plus expected development on reported claims 52                  
Reinsurance | Marine and aviation | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 40,827 40,900 43,243 46,612 41,363 42,961 55,299      
Total of incurred-but-not-reported liabilities plus expected development on reported claims 43                  
Reinsurance | Marine and aviation | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 48,477 47,066 43,540 27,006 27,454 18,906        
Total of incurred-but-not-reported liabilities plus expected development on reported claims 35                  
Reinsurance | Marine and aviation | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 84,756 81,628 79,801 82,194 69,806          
Total of incurred-but-not-reported liabilities plus expected development on reported claims 5,560                  
Reinsurance | Marine and aviation | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 37,098 37,892 41,766 40,298            
Total of incurred-but-not-reported liabilities plus expected development on reported claims 308                  
Reinsurance | Marine and aviation | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 35,672 40,830 43,763              
Total of incurred-but-not-reported liabilities plus expected development on reported claims 2,976                  
Reinsurance | Marine and aviation | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 59,227 68,907                
Total of incurred-but-not-reported liabilities plus expected development on reported claims 32,375                  
Reinsurance | Marine and aviation | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 40,951                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 34,539                  
Reinsurance | Professional lines                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 1,929,998                  
Reinsurance | Professional lines | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 246,043 234,311 226,234 228,193 229,556 233,169 218,847 219,052 219,123 219,162
Total of incurred-but-not-reported liabilities plus expected development on reported claims 13,578                  
Reinsurance | Professional lines | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 252,022 241,113 235,131 228,410 231,352 224,649 213,993 211,774 211,820  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 16,515                  
Reinsurance | Professional lines | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 278,699 266,979 255,012 255,088 227,468 199,715 196,073 195,019    
Total of incurred-but-not-reported liabilities plus expected development on reported claims 26,195                  
Reinsurance | Professional lines | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 239,324 210,303 187,761 177,819 161,694 155,470 154,889      
Total of incurred-but-not-reported liabilities plus expected development on reported claims 38,070                  
Reinsurance | Professional lines | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 195,575 173,954 165,981 155,390 148,458 145,994        
Total of incurred-but-not-reported liabilities plus expected development on reported claims 24,160                  
Reinsurance | Professional lines | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 157,572 146,088 141,610 137,723 138,048          
Total of incurred-but-not-reported liabilities plus expected development on reported claims 36,200                  
Reinsurance | Professional lines | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 134,478 136,107 141,559 140,886            
Total of incurred-but-not-reported liabilities plus expected development on reported claims 69,314                  
Reinsurance | Professional lines | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 136,381 140,737 148,950              
Total of incurred-but-not-reported liabilities plus expected development on reported claims 93,845                  
Reinsurance | Professional lines | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 153,853 169,576                
Total of incurred-but-not-reported liabilities plus expected development on reported claims 125,013                  
Reinsurance | Professional lines | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 136,051                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 124,516                  
Reinsurance | Liability                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 3,025,283                  
Reinsurance | Liability | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 193,578 189,047 183,101 187,245 196,747 198,893 200,138 204,240 202,526 199,575
Total of incurred-but-not-reported liabilities plus expected development on reported claims 14,361                  
Reinsurance | Liability | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 217,019 206,204 203,268 213,485 213,256 215,461 215,633 214,689 214,346  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 22,070                  
Reinsurance | Liability | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 315,793 274,615 267,241 263,195 253,525 250,247 245,286 239,971    
Total of incurred-but-not-reported liabilities plus expected development on reported claims 46,678                  
Reinsurance | Liability | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 343,290 306,648 297,380 287,818 279,262 270,080 275,306      
Total of incurred-but-not-reported liabilities plus expected development on reported claims 62,419                  
Reinsurance | Liability | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 352,697 307,032 286,876 274,110 268,812 264,003        
Total of incurred-but-not-reported liabilities plus expected development on reported claims 72,183                  
Reinsurance | Liability | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 331,729 272,905 274,393 272,513 263,522          
Total of incurred-but-not-reported liabilities plus expected development on reported claims 103,836                  
Reinsurance | Liability | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 306,011 278,743 284,216 283,606            
Total of incurred-but-not-reported liabilities plus expected development on reported claims 148,977                  
Reinsurance | Liability | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 346,161 311,735 304,160              
Total of incurred-but-not-reported liabilities plus expected development on reported claims 185,421                  
Reinsurance | Liability | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 343,773 347,387                
Total of incurred-but-not-reported liabilities plus expected development on reported claims 232,850                  
Reinsurance | Liability | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 275,232                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 241,263                  
Reinsurance | Agriculture                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 1,146,317                  
Reinsurance | Agriculture | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 162,927 162,762 162,068 162,245 162,327 162,314 162,388 162,820 164,351 183,260
Total of incurred-but-not-reported liabilities plus expected development on reported claims 482                  
Reinsurance | Agriculture | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 96,251 95,634 95,503 95,516 95,339 95,332 95,346 95,608 103,199  
Total of incurred-but-not-reported liabilities plus expected development on reported claims (27)                  
Reinsurance | Agriculture | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 109,763 109,012 109,068 109,863 109,633 111,045 117,960 124,229    
Total of incurred-but-not-reported liabilities plus expected development on reported claims (72)                  
Reinsurance | Agriculture | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 136,658 137,516 138,984 139,510 138,439 144,401 151,768      
Total of incurred-but-not-reported liabilities plus expected development on reported claims (60)                  
Reinsurance | Agriculture | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 142,760 139,989 140,618 140,883 147,359 141,040        
Total of incurred-but-not-reported liabilities plus expected development on reported claims 646                  
Reinsurance | Agriculture | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 183,092 183,384 187,770 185,345 185,560          
Total of incurred-but-not-reported liabilities plus expected development on reported claims 93                  
Reinsurance | Agriculture | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 61,986 63,874 62,837 62,678            
Total of incurred-but-not-reported liabilities plus expected development on reported claims 1,130                  
Reinsurance | Agriculture | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 57,857 61,437 69,823              
Total of incurred-but-not-reported liabilities plus expected development on reported claims 6,144                  
Reinsurance | Agriculture | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 91,534 101,082                
Total of incurred-but-not-reported liabilities plus expected development on reported claims 16,972                  
Reinsurance | Agriculture | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 103,489                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 81,193                  
Reinsurance | Credit and surety                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 893,476                  
Reinsurance | Credit and surety | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 111,511 120,790 120,482 121,780 125,477 126,744 137,973 141,621 134,527 134,434
Total of incurred-but-not-reported liabilities plus expected development on reported claims 1,914                  
Reinsurance | Credit and surety | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 129,333 132,989 138,726 137,528 136,568 155,217 159,148 164,350 159,274  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 1,447                  
Reinsurance | Credit and surety | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 112,465 110,316 112,631 114,957 122,495 147,955 140,188 140,892    
Total of incurred-but-not-reported liabilities plus expected development on reported claims 35                  
Reinsurance | Credit and surety | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 114,612 114,131 114,412 117,044 125,763 131,630 137,832      
Total of incurred-but-not-reported liabilities plus expected development on reported claims 2,647                  
Reinsurance | Credit and surety | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 94,229 105,503 110,531 113,535 119,227 111,022        
Total of incurred-but-not-reported liabilities plus expected development on reported claims 4,053                  
Reinsurance | Credit and surety | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 57,322 65,573 67,759 67,825 74,101          
Total of incurred-but-not-reported liabilities plus expected development on reported claims 6,315                  
Reinsurance | Credit and surety | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 94,943 68,987 83,559 76,917            
Total of incurred-but-not-reported liabilities plus expected development on reported claims 8,385                  
Reinsurance | Credit and surety | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 41,463 43,967 52,005              
Total of incurred-but-not-reported liabilities plus expected development on reported claims 13,732                  
Reinsurance | Credit and surety | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 51,231 63,653                
Total of incurred-but-not-reported liabilities plus expected development on reported claims 33,129                  
Reinsurance | Credit and surety | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 86,367                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 64,350                  
Reinsurance | Motor                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 2,347,869                  
Reinsurance | Motor | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 161,844 162,730 161,835 162,212 165,481 168,796 173,139 175,983 180,792 181,056
Total of incurred-but-not-reported liabilities plus expected development on reported claims 2,346                  
Reinsurance | Motor | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 204,673 206,090 205,780 208,620 209,908 220,820 219,055 215,201 221,182  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 8,979                  
Reinsurance | Motor | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 245,098 244,553 240,717 243,353 251,675 261,592 259,912 244,395    
Total of incurred-but-not-reported liabilities plus expected development on reported claims 4,366                  
Reinsurance | Motor | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 361,134 354,392 359,026 358,286 357,741 368,517 361,782      
Total of incurred-but-not-reported liabilities plus expected development on reported claims 22,422                  
Reinsurance | Motor | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 361,117 348,323 360,907 364,664 353,384 355,561        
Total of incurred-but-not-reported liabilities plus expected development on reported claims 17,400                  
Reinsurance | Motor | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 332,952 328,522 337,404 336,957 338,031          
Total of incurred-but-not-reported liabilities plus expected development on reported claims 12,894                  
Reinsurance | Motor | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 197,439 215,572 218,224 215,257            
Total of incurred-but-not-reported liabilities plus expected development on reported claims 10,872                  
Reinsurance | Motor | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 184,244 182,010 180,372              
Total of incurred-but-not-reported liabilities plus expected development on reported claims 25,813                  
Reinsurance | Motor | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 173,870 160,697                
Total of incurred-but-not-reported liabilities plus expected development on reported claims 35,986                  
Reinsurance | Motor | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 125,498                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 60,323                  
Reinsurance | Run-off lines                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 3,729,943                  
Reinsurance | Run-off lines | Accident Year 2014                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 219,012 218,896 219,748 219,953 223,970 224,135 227,865 236,768 246,616 $ 242,347
Total of incurred-but-not-reported liabilities plus expected development on reported claims 201                  
Reinsurance | Run-off lines | Accident Year 2015                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 244,790 247,183 249,050 251,245 246,266 247,377 256,665 256,648 $ 267,709  
Total of incurred-but-not-reported liabilities plus expected development on reported claims 475                  
Reinsurance | Run-off lines | Accident Year 2016                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 274,291 281,137 281,204 280,836 277,349 282,705 285,973 $ 286,264    
Total of incurred-but-not-reported liabilities plus expected development on reported claims 2,838                  
Reinsurance | Run-off lines | Accident Year 2017                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 722,172 729,812 739,258 741,278 740,074 702,378 $ 705,205      
Total of incurred-but-not-reported liabilities plus expected development on reported claims 19,886                  
Reinsurance | Run-off lines | Accident Year 2018                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 600,640 600,516 614,573 628,722 614,222 $ 523,351        
Total of incurred-but-not-reported liabilities plus expected development on reported claims 15,506                  
Reinsurance | Run-off lines | Accident Year 2019                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 387,944 395,134 411,886 432,299 $ 448,745          
Total of incurred-but-not-reported liabilities plus expected development on reported claims 17,304                  
Reinsurance | Run-off lines | Accident Year 2020                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 553,124 548,846 553,538 $ 520,537            
Total of incurred-but-not-reported liabilities plus expected development on reported claims 41,243                  
Reinsurance | Run-off lines | Accident Year 2021                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 438,082 441,530 $ 430,820              
Total of incurred-but-not-reported liabilities plus expected development on reported claims 39,301                  
Reinsurance | Run-off lines | Accident Year 2022                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 225,697 $ 265,797                
Total of incurred-but-not-reported liabilities plus expected development on reported claims 47,820                  
Reinsurance | Run-off lines | Accident Year 2023                    
Claims Development [Line Items]                    
Incurred claims and allocated claim adjustment expenses 64,191                  
Total of incurred-but-not-reported liabilities plus expected development on reported claims $ 28,272