XML 117 R92.htm IDEA: XBRL DOCUMENT v3.8.0.1
RESERVE FOR LOSSES AND LOSS EXPENSES - Cumulative paid claims and allocated claim adjustment expenses, net of reinsurance (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2008
Claims Development [Line Items]                    
Liabilities for claims and claim adjustment expenses, net of reinsurance $ 9,654,715                  
Aviabel                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 26,830                  
All outstanding liabilities before 2008, net of reinsurance 10,626                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 77,405                  
Aviabel | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (33)                  
Aviabel | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 1                  
Aviabel | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 97                  
Aviabel | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 20                  
Aviabel | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 661                  
Aviabel | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 425                  
Aviabel | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 1,944                  
Aviabel | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 3,291                  
Aviabel | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,453                  
Aviabel | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 14,970                  
Novae                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 139,427                  
All outstanding liabilities before 2008, net of reinsurance 102,164                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 1,300,361                  
Novae | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 1,458                  
Novae | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 1,147                  
Novae | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 3,197                  
Novae | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 4,332                  
Novae | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 7,352                  
Novae | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,878                  
Novae | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 12,370                  
Novae | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 19,349                  
Novae | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 51,065                  
Novae | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 33,278                  
Insurance                    
Claims Development [Line Items]                    
Liabilities for claims and claim adjustment expenses, net of reinsurance 3,331,536                  
Insurance | Property and Other                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 2,930,352                  
All outstanding liabilities before 2008, net of reinsurance 3,875                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 880,954                  
Insurance | Property and Other | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 214,663 $ 215,071 $ 215,121 $ 215,628 $ 213,569 $ 211,002 $ 184,038 $ 172,320 $ 150,470 $ 76,558
Insurance | Property and Other | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 77,466 77,187 76,865 74,636 73,538 72,622 68,768 60,166 31,379  
Insurance | Property and Other | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 110,763 110,709 110,934 110,785 106,593 95,747 87,059 48,624    
Insurance | Property and Other | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 299,248 298,559 298,766 299,567 277,260 217,578 87,525      
Insurance | Property and Other | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 379,696 374,485 366,854 343,503 278,870 107,358        
Insurance | Property and Other | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 372,338 361,209 347,531 304,207 129,157          
Insurance | Property and Other | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 401,482 393,868 341,023 169,961            
Insurance | Property and Other | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 317,850 281,377 123,126              
Insurance | Property and Other | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 442,007 174,455                
Insurance | Property and Other | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 314,839                  
Insurance | Marine                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 536,047                  
All outstanding liabilities before 2008, net of reinsurance 8,213                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 213,390                  
Insurance | Marine | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 82,344 82,339 82,259 82,128 82,043 78,313 77,203 69,114 52,697 14,357
Insurance | Marine | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 49,060 48,712 48,430 45,896 45,286 43,243 39,699 30,364 17,431  
Insurance | Marine | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 43,587 47,088 46,150 45,373 42,554 33,392 28,771 18,062    
Insurance | Marine | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 64,750 60,523 59,816 57,972 54,874 44,168 26,417      
Insurance | Marine | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 52,833 50,448 49,631 44,858 38,560 10,730        
Insurance | Marine | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 66,326 63,637 55,414 44,437 19,313          
Insurance | Marine | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 26,977 26,831 15,277 6,363            
Insurance | Marine | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 108,071 54,845 21,467              
Insurance | Marine | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 32,038 12,497                
Insurance | Marine | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 10,061                  
Insurance | Aviation                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 114,861                  
All outstanding liabilities before 2008, net of reinsurance 1,611                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 56,400                  
Insurance | Aviation | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 5,519 5,526 5,269 4,663 4,487 4,216 3,666 3,084 2,063 488
Insurance | Aviation | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 13,547 13,755 14,258 14,322 13,957 12,834 7,071 3,628 2,118  
Insurance | Aviation | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 8,247 8,152 7,708 7,586 6,920 6,341 4,156 1,053    
Insurance | Aviation | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 6,056 5,826 5,576 5,040 4,521 2,830 639      
Insurance | Aviation | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 7,070 6,836 5,958 4,159 2,868 957        
Insurance | Aviation | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 13,551 11,462 9,757 7,336 4,402          
Insurance | Aviation | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 13,914 11,706 8,033 3,989            
Insurance | Aviation | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 21,095 16,177 8,090              
Insurance | Aviation | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 19,403 10,421                
Insurance | Aviation | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 6,459                  
Insurance | Credit and Political Risk                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 631,553                  
All outstanding liabilities before 2008, net of reinsurance (1,475)                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 51,469                  
Insurance | Credit and Political Risk | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 44,161 44,410 44,410 44,410 45,379 45,379 45,638 45,625 69,217 0
Insurance | Credit and Political Risk | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 340,809 345,592 345,545 345,545 341,600 346,243 346,267 344,658 92,844  
Insurance | Credit and Political Risk | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 102,200 102,158 101,952 101,790 106,769 90,729 85,418 50,000    
Insurance | Credit and Political Risk | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 27,631 27,636 27,636 27,636 27,636 37,205 32,788      
Insurance | Credit and Political Risk | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 42 40 0 0 0 0        
Insurance | Credit and Political Risk | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 11,768 5,216 3,726 2,235 745          
Insurance | Credit and Political Risk | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 57,855 61,108 39,952 1,924            
Insurance | Credit and Political Risk | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 23,298 23,309 0              
Insurance | Credit and Political Risk | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 23,789 0                
Insurance | Credit and Political Risk | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 0                  
Insurance | Professional Lines                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 1,741,257                  
All outstanding liabilities before 2008, net of reinsurance 30,546                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 1,559,564                  
Insurance | Professional Lines | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 268,487 267,611 249,321 214,481 189,339 167,828 124,681 68,197 22,325 4,068
Insurance | Professional Lines | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 179,770 167,129 127,033 107,421 97,061 69,050 44,312 20,670 1,689  
Insurance | Professional Lines | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 115,204 110,156 99,554 89,051 72,840 53,738 27,880 7,857    
Insurance | Professional Lines | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 283,718 238,523 165,755 108,470 74,224 32,351 6,782      
Insurance | Professional Lines | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 255,140 231,963 185,059 100,526 41,545 7,824        
Insurance | Professional Lines | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 214,534 176,899 130,342 73,334 17,739          
Insurance | Professional Lines | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 194,294 131,610 71,510 23,665            
Insurance | Professional Lines | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 138,967 68,400 20,403              
Insurance | Professional Lines | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 71,619 16,010                
Insurance | Professional Lines | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 19,524                  
Insurance | Liability                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 560,061                  
All outstanding liabilities before 2008, net of reinsurance 44,150                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 569,759                  
Insurance | Liability | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 87,159 61,618 55,314 51,776 47,447 37,408 27,861 18,507 8,796 1,906
Insurance | Liability | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 84,427 83,991 44,105 41,323 31,865 26,754 13,305 4,646 726  
Insurance | Liability | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 86,471 71,814 66,140 61,055 53,604 30,809 15,986 1,029    
Insurance | Liability | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 60,263 54,996 46,074 38,377 20,190 10,540 2,761      
Insurance | Liability | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 42,745 37,140 30,146 15,412 5,515 1,631        
Insurance | Liability | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 60,021 42,055 33,324 23,285 2,363          
Insurance | Liability | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 71,630 49,858 18,662 1,419            
Insurance | Liability | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 39,767 22,474 5,439              
Insurance | Liability | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 23,335 6,332                
Insurance | Liability | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 4,243                  
Reinsurance                    
Claims Development [Line Items]                    
Liabilities for claims and claim adjustment expenses, net of reinsurance 4,945,413                  
Reinsurance | Property and Other                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 4,037,613                  
All outstanding liabilities before 2008, net of reinsurance 6,225                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 1,220,069                  
Reinsurance | Property and Other | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 517,657 519,391 519,711 514,765 514,696 510,305 497,078 444,047 316,280 158,206
Reinsurance | Property and Other | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 193,973 197,310 195,614 192,746 193,309 182,556 164,047 132,309 57,796  
Reinsurance | Property and Other | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 551,588 546,253 521,377 491,817 444,822 412,731 318,198 119,385    
Reinsurance | Property and Other | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 991,307 976,120 902,188 872,086 769,142 561,377 242,494      
Reinsurance | Property and Other | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 351,558 341,925 327,361 305,020 231,961 93,847        
Reinsurance | Property and Other | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 374,944 365,089 336,940 223,666 55,047          
Reinsurance | Property and Other | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 369,000 351,496 274,886 65,848            
Reinsurance | Property and Other | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 282,967 190,057 48,116              
Reinsurance | Property and Other | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 231,682 78,916                
Reinsurance | Property and Other | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 172,937                  
Reinsurance | Credit and Surety                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 878,286                  
All outstanding liabilities before 2008, net of reinsurance 10,351                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 375,762                  
Reinsurance | Credit and Surety | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 94,601 94,446 94,040 93,282 91,014 88,604 86,796 71,501 70,349 20,891
Reinsurance | Credit and Surety | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 89,986 89,894 89,921 89,736 87,079 83,138 80,744 78,254 32,888  
Reinsurance | Credit and Surety | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 68,294 67,252 65,722 64,455 62,586 61,983 50,148 28,387    
Reinsurance | Credit and Surety | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 91,307 88,944 86,653 82,015 74,037 56,106 22,640      
Reinsurance | Credit and Surety | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 114,251 112,423 108,858 102,976 88,092 50,516        
Reinsurance | Credit and Surety | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 108,839 101,104 94,347 78,976 32,708          
Reinsurance | Credit and Surety | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 97,957 88,668 62,900 35,839            
Reinsurance | Credit and Surety | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 103,123 84,077 33,064              
Reinsurance | Credit and Surety | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 75,170 42,348                
Reinsurance | Credit and Surety | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 34,758                  
Reinsurance | Professional Lines                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 863,782                  
All outstanding liabilities before 2008, net of reinsurance 34,882                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 1,119,534                  
Reinsurance | Professional Lines | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 139,917 133,596 124,658 109,093 92,320 70,815 49,393 21,736 6,465 373
Reinsurance | Professional Lines | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 143,634 138,823 128,608 108,787 83,946 63,180 32,327 8,589 914  
Reinsurance | Professional Lines | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 130,837 124,158 107,534 76,931 52,187 31,269 12,037 1,759    
Reinsurance | Professional Lines | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 120,076 103,309 85,052 57,402 30,326 11,829 1,506      
Reinsurance | Professional Lines | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 107,581 86,211 53,801 29,730 10,441 780        
Reinsurance | Professional Lines | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 81,940 65,195 30,666 12,121 1,068          
Reinsurance | Professional Lines | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 74,748 48,930 13,085 2,020            
Reinsurance | Professional Lines | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 41,610 13,507 3,134              
Reinsurance | Professional Lines | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 20,624 1,782                
Reinsurance | Professional Lines | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 2,815                  
Reinsurance | Motor                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 760,256                  
All outstanding liabilities before 2008, net of reinsurance 129,548                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 1,082,423                  
Reinsurance | Motor | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 17,657 17,231 15,570 14,897 12,088 9,491 7,910 6,625 6,371 3,093
Reinsurance | Motor | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 30,378 27,248 22,446 20,029 13,627 10,020 8,428 7,134 2,819  
Reinsurance | Motor | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 35,444 34,342 30,942 26,489 22,873 19,189 13,316 7,406    
Reinsurance | Motor | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 90,871 85,995 79,729 72,663 61,691 46,277 21,274      
Reinsurance | Motor | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 91,896 87,658 80,891 70,634 55,282 29,727        
Reinsurance | Motor | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 87,407 81,419 70,849 56,009 34,607          
Reinsurance | Motor | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 107,090 98,483 77,736 44,225            
Reinsurance | Motor | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 118,902 97,495 58,884              
Reinsurance | Motor | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 109,559 61,938                
Reinsurance | Motor | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 71,052                  
Reinsurance | Liability                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 807,122                  
All outstanding liabilities before 2008, net of reinsurance 42,182                  
Liabilities for claims and claim adjustment expenses, net of reinsurance 1,147,625                  
Reinsurance | Liability | Accident Year 2008                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 63,903 58,022 53,882 51,922 43,509 36,567 30,028 21,953 9,952 $ 2,160
Reinsurance | Liability | Accident Year 2009                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 135,031 129,644 125,329 105,410 73,521 56,730 44,552 17,104 $ 1,705  
Reinsurance | Liability | Accident Year 2010                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 119,872 108,938 97,617 83,976 62,300 46,207 17,659 $ 2,484    
Reinsurance | Liability | Accident Year 2011                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 123,719 112,581 92,696 70,283 40,021 21,297 $ 5,191      
Reinsurance | Liability | Accident Year 2012                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 101,343 78,368 58,855 28,418 12,809 $ 3,542        
Reinsurance | Liability | Accident Year 2013                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 88,327 69,098 52,360 22,259 $ 5,978          
Reinsurance | Liability | Accident Year 2014                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 70,389 48,498 28,699 $ 7,117            
Reinsurance | Liability | Accident Year 2015                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 54,646 27,473 $ 7,273              
Reinsurance | Liability | Accident Year 2016                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 37,819 $ 11,891                
Reinsurance | Liability | Accident Year 2017                    
Claims Development [Line Items]                    
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance $ 12,073