XML 83 R66.htm IDEA: XBRL DOCUMENT
v3.20.4

Short Duration Contracts - Claims development - Reinsurance (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Liabilities for losses and loss adjustment expenses, net of reinsurance | $ 11,923,393 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 2,483,009 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 901,474 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2008, net of reinsurance | 303,572 |  |  |  |  |  |  |  |  |
Liabilities for losses and loss adjustment expenses, net of reinsurance | 1,885,107 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2011 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 126,543 | $ 130,769 | $ 129,307 | $ 132,142 | $ 138,257 | $ 141,023 | $ 145,259 | $ 149,799 | $ 155,796 | $ 152,359
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 87,463 | 82,728 | 76,722 | 71,457 | 64,486 | 55,027 | 38,998 | 21,684 | 11,509 | 2,353
Total of IBNR liabilities plus expected development on reported claims | 16,905 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2012 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 122,312 | 123,884 | 120,655 | 111,938 | 117,551 | 127,563 | 139,762 | 143,950 | 145,770 |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 76,287 | 70,308 | 59,877 | 48,109 | 36,809 | 25,738 | 14,875 | 8,637 | 1,371 |
Total of IBNR liabilities plus expected development on reported claims | 28,208 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2013 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 137,978 | 133,857 | 137,591 | 139,221 | 151,340 | 157,804 | 161,993 | 168,738 |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 77,089 | 71,150 | 63,415 | 54,797 | 43,263 | 23,209 | 10,050 | 2,549 |  |
Total of IBNR liabilities plus expected development on reported claims | 37,566 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2014 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 243,067 | 242,792 | 233,033 | 236,505 | 222,220 | 224,801 | 219,506 |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 135,101 | 114,798 | 91,366 | 63,636 | 40,949 | 16,160 | 3,962 |  |  |
Total of IBNR liabilities plus expected development on reported claims | 48,039 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2015 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 251,747 | 244,861 | 240,886 | 233,644 | 224,525 | 225,908 |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 120,889 | 97,007 | 71,231 | 47,381 | 20,340 | 4,490 |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 63,133 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2016 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 275,966 | 268,880 | 254,032 | 229,862 | 217,499 |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 114,096 | 86,989 | 51,822 | 25,720 | 5,763 |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 65,394 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2017 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 297,998 | 269,434 | 253,959 | 268,353 |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 108,591 | 59,377 | 29,414 | 6,441 |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 79,858 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2018 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 286,944 | 296,507 | 282,010 |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 106,454 | 31,118 | 7,588 |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 81,666 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2019 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 347,126 | 338,581 |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 57,682 | 15,824 |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 178,981 |  |  |  |  |  |  |  |  |
Reinsurance | Casualty | 2020 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 393,328 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 17,822 |  |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 333,679 |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 696,183 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 421,635 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2008, net of reinsurance | 1,624 |  |  |  |  |  |  |  |  |
Liabilities for losses and loss adjustment expenses, net of reinsurance | 276,172 |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2011 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 150,459 | 150,971 | 152,082 | 156,150 | 158,465 | 159,174 | 162,993 | 176,170 | 195,232 | 215,493
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 148,403 | 148,929 | 148,338 | 147,929 | 145,774 | 143,141 | 137,400 | 122,060 | 89,042 | 63,175
Total of IBNR liabilities plus expected development on reported claims | 0 |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2012 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 96,637 | 97,252 | 97,143 | 99,178 | 99,998 | 102,254 | 108,787 | 123,288 | 150,570 |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 95,521 | 95,419 | 94,732 | 94,122 | 92,993 | 90,834 | 83,929 | 70,843 | 25,850 |
Total of IBNR liabilities plus expected development on reported claims | 132 |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2013 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 29,060 | 28,910 | 29,848 | 30,567 | 33,143 | 37,714 | 49,507 | 69,044 |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 29,846 | 29,119 | 29,117 | 28,859 | 26,953 | 24,911 | 19,701 | 12,283 |  |
Total of IBNR liabilities plus expected development on reported claims | (132) |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2014 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 20,845 | 20,957 | 21,671 | 23,491 | 26,438 | 32,188 | 46,774 |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 20,146 | 19,993 | 19,786 | 20,170 | 19,293 | 20,635 | 13,702 |  |  |
Total of IBNR liabilities plus expected development on reported claims | (10) |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2015 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 4,102 | 4,746 | 6,643 | 12,724 | 19,282 | 34,895 |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 2,630 | 2,537 | 2,959 | 2,660 | (1,825) | (3,161) |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 67 |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2016 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 9,027 | 11,487 | 15,313 | 19,556 | 26,671 |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 3,803 | 4,515 | 3,057 | 2,646 | (6,752) |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 1,302 |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2017 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 32,747 | 46,354 | 49,340 | 82,521 |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 24,209 | 34,534 | 30,224 | 30,173 |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 87 |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2018 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 44,448 | 63,106 | 75,309 |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 26,189 | 14,232 | 25,505 |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 5,855 |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2019 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 35,789 | 51,202 |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 17,393 | 3,878 |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 9,545 |  |  |  |  |  |  |  |  |
Reinsurance | Property catastrophe | 2020 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 273,069 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 53,495 |  |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 50,368 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 1,781,941 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 1,206,994 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2008, net of reinsurance | 6,125 |  |  |  |  |  |  |  |  |
Liabilities for losses and loss adjustment expenses, net of reinsurance | 581,072 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2011 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 152,753 | 154,261 | 155,606 | 156,647 | 158,952 | 160,264 | 164,414 | 168,122 | 180,624 | 208,318
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 150,417 | 151,322 | 150,302 | 150,028 | 149,788 | 148,684 | 146,626 | 142,081 | 122,137 | 47,949
Total of IBNR liabilities plus expected development on reported claims | 801 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2012 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 103,596 | 109,122 | 111,722 | 113,201 | 115,425 | 119,838 | 124,408 | 122,552 | 156,980 |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 103,076 | 103,216 | 103,274 | 104,091 | 103,452 | 102,445 | 93,752 | 78,416 | 26,158 |
Total of IBNR liabilities plus expected development on reported claims | 251 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2013 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 63,769 | 62,949 | 64,162 | 64,950 | 66,669 | 71,100 | 77,474 | 116,130 |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 62,591 | 61,601 | 56,090 | 54,202 | 53,389 | 50,208 | 43,068 | 26,068 |  |
Total of IBNR liabilities plus expected development on reported claims | 770 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2014 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 82,899 | 84,679 | 88,994 | 91,272 | 99,891 | 118,056 | 144,299 |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 79,009 | 79,146 | 78,753 | 77,098 | 72,133 | 63,144 | 23,641 |  |  |
Total of IBNR liabilities plus expected development on reported claims | 2,063 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2015 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 177,928 | 188,992 | 189,702 | 185,288 | 189,735 | 215,856 |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 160,271 | 166,632 | 161,447 | 150,207 | 119,578 | 75,725 |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 12,275 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2016 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 141,789 | 138,008 | 139,032 | 147,154 | 178,103 |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 113,336 | 105,486 | 99,954 | 96,174 | 33,418 |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 15,986 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2017 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 223,442 | 231,062 | 245,333 | 262,387 |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 156,523 | 148,638 | 118,658 | 25,807 |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 17,528 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2018 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 238,162 | 241,754 | 223,917 |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 153,599 | 108,263 | 29,724 |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 18,520 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2019 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 209,696 | 219,130 |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 125,698 | 43,809 |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 32,266 |  |  |  |  |  |  |  |  |
Reinsurance | Property excluding property catastrophe | 2020 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 387,907 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 102,474 |  |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 167,596 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 349,883 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 183,055 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2008, net of reinsurance | 16,534 |  |  |  |  |  |  |  |  |
Liabilities for losses and loss adjustment expenses, net of reinsurance | 183,362 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2011 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 23,517 | 23,792 | 24,871 | 27,264 | 27,213 | 28,811 | 32,436 | 35,889 | 32,956 | 39,359
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 21,979 | 21,973 | 21,911 | 21,988 | 16,634 | 15,959 | 19,235 | 16,530 | 12,122 | 4,421
Total of IBNR liabilities plus expected development on reported claims | 1,317 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2012 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 41,316 | 43,165 | 46,183 | 49,865 | 51,223 | 52,428 | 55,172 | 58,956 | 59,117 |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 38,257 | 38,164 | 37,871 | 36,379 | 35,174 | 33,428 | 27,623 | 11,480 | 2,664 |
Total of IBNR liabilities plus expected development on reported claims | 2,228 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2013 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 31,087 | 34,806 | 35,248 | 35,993 | 36,101 | 37,545 | 38,509 | 39,538 |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 24,520 | 24,804 | 24,427 | 23,135 | 22,111 | 19,075 | 14,330 | 5,109 |  |
Total of IBNR liabilities plus expected development on reported claims | 5,039 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2014 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 22,347 | 23,695 | 24,050 | 26,059 | 27,763 | 29,576 | 31,333 |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 16,253 | 15,376 | 14,939 | 12,748 | 11,872 | 8,221 | 4,373 |  |  |
Total of IBNR liabilities plus expected development on reported claims | 5,044 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2015 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 28,618 | 30,964 | 31,910 | 31,953 | 37,875 | 34,066 |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 22,456 | 22,773 | 20,971 | 19,120 | 13,476 | 11 |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 4,738 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2016 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 17,029 | 19,344 | 23,622 | 22,804 | 27,409 |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 5,900 | 3,292 | 552 | (1,655) | (7,300) |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 8,230 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2017 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 20,853 | 23,878 | 26,407 | 28,868 |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 11,037 | 9,372 | 6,546 | 1,659 |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 6,783 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2018 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 24,957 | 26,395 | 28,355 |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 11,384 | 7,087 | 2,006 |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 7,490 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2019 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 55,921 | 49,466 |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 21,930 | 11,015 |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 17,208 |  |  |  |  |  |  |  |  |
Reinsurance | Marine and aviation | 2020 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 84,238 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 9,339 |  |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 58,896 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 2,657,098 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 1,759,059 |  |  |  |  |  |  |  |  |
All outstanding liabilities before 2008, net of reinsurance | 8,956 |  |  |  |  |  |  |  |  |
Liabilities for losses and loss adjustment expenses, net of reinsurance | 906,995 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2011 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 87,648 | 89,163 | 88,820 | 90,727 | 91,334 | 92,703 | 94,512 | 96,117 | 100,395 | 115,554
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 85,854 | 85,643 | 85,960 | 84,815 | 82,468 | 80,642 | 77,018 | 72,298 | 59,715 | $ 29,717
Total of IBNR liabilities plus expected development on reported claims | 1,058 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2012 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 187,908 | 196,309 | 202,085 | 203,898 | 200,945 | 203,114 | 209,355 | 219,627 | 231,531 |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 179,943 | 179,614 | 177,742 | 173,202 | 169,096 | 161,073 | 149,753 | 126,138 | $ 47,484 |
Total of IBNR liabilities plus expected development on reported claims | 4,635 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2013 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 210,455 | 216,579 | 216,861 | 219,314 | 218,354 | 222,046 | 232,427 | 259,594 |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 189,147 | 188,746 | 181,279 | 175,892 | 166,100 | 149,617 | 122,813 | $ 58,962 |  |
Total of IBNR liabilities plus expected development on reported claims | 10,351 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2014 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 250,825 | 255,341 | 253,373 | 258,595 | 265,417 | 263,653 | 283,138 |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 221,978 | 219,234 | 207,965 | 201,189 | 187,560 | 151,115 | $ 71,006 |  |  |
Total of IBNR liabilities plus expected development on reported claims | 15,127 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2015 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 201,046 | 204,458 | 204,179 | 207,220 | 208,927 | 217,666 |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 168,314 | 160,243 | 150,969 | 143,690 | 118,770 | $ 56,438 |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 19,996 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2016 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 223,777 | 217,054 | 222,788 | 228,501 | 231,160 |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 192,947 | 180,542 | 168,425 | 143,624 | $ 67,730 |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 18,179 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2017 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 259,041 | 260,051 | 271,084 | 282,024 |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 209,005 | 201,378 | 171,632 | $ 76,847 |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 40,904 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2018 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 326,027 | 334,567 | 338,298 |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 243,257 | 211,954 | $ 75,395 |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 53,316 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2019 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 358,997 | 378,545 |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 167,055 | $ 84,416 |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | 80,438 |  |  |  |  |  |  |  |  |
Reinsurance | Other specialty | 2020 |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred losses and allocated loss adjustment expenses, net of reinsurance | 551,374 |  |  |  |  |  |  |  |  |
Cumulative paid losses and allocated loss adjustment expenses, net of reinsurance | 101,559 |  |  |  |  |  |  |  |  |
Total of IBNR liabilities plus expected development on reported claims | $ 259,496 |  |  |  |  |  |  |  |  |

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ClaimsDevelopmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, after reinsurance, of paid claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116884468&loc=SL65671311-158438 + Details
Name: | us-gaap_ShortdurationInsuranceContractsCumulativePaidClaimsAndAllocatedClaimAdjustmentExpenseNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Undiscounted amount, after reinsurance, of incurred-but-not-reported (IBNR) liabilities plus expected development on reported claims, for claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4E -URI http://asc.fasb.org/extlink&oid=116884468&loc=SL65671321-158438 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4D -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=116884468&loc=SL65671317-158438 + Details
Name: | us-gaap_ShortdurationInsuranceContractsIncurredButNotReportedIbnrClaimsLiabilityNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Undiscounted amount, after reinsurance, of incurred claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=116884468&loc=SL65671311-158438 + Details
Name: | us-gaap_ShortdurationInsuranceContractsIncurredClaimsAndAllocatedClaimAdjustmentExpenseNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=116884468&loc=SL65671315-158438 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=116884468&loc=SL65671311-158438 + Details
Name: | us-gaap_ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts for accident years not separately presented in claim development information. Excludes unallocated claim adjustment expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=116884468&loc=SL65671311-158438 + Details
Name: | us-gaap_ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNetNotSeparatelyPresented
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=acgl_ReinsuranceSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=acgl_CasualtyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2011Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2012Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2013Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2014Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2015Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2016Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractsAccidentYear2017Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractsAccidentYear2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=acgl_PropertyCatastropheMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=acgl_PropertyExcludingPropertyCatastropheMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=acgl_MarineAndAviationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ProductOrServiceAxis=acgl_OtherSpecialtyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |