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Liability for Losses and Loss Expenses - Summary of Incurred and Paid Claims Development, Net of Reinsurance (Detail) Claims in Thousands, $ in Thousands | Dec. 31, 2019 USD ($) Claims | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($) | Dec. 31, 2012 USD ($) | Dec. 31, 2011 USD ($) | Dec. 31, 2010 USD ($)
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Personal Automobile [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 1,468,469 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2010 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | 118,294 | $ 118,314 | $ 118,289 | $ 118,385 | $ 118,587 | $ 118,916 | $ 118,876 | $ 118,562 | $ 117,552 | $ 117,967
Total IBNR Plus Expected Development on Reported Claims | $ 27 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 70 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2011 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 133,207 | 133,142 | 133,145 | 133,218 | 133,617 | 133,229 | 132,987 | 131,678 | 127,929 |
Total IBNR Plus Expected Development on Reported Claims | $ 73 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 75 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2012 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 136,677 | 136,141 | 136,463 | 136,552 | 136,493 | 135,592 | 133,201 | 130,415 |  |
Total IBNR Plus Expected Development on Reported Claims | $ 215 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 69 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2013 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 132,853 | 132,934 | 132,604 | 132,643 | 131,594 | 130,737 | 124,965 |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 175 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 66 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2014 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 126,734 | 126,779 | 126,200 | 124,210 | 124,806 | 124,426 |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 264 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 71 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2015 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 142,408 | 142,493 | 139,181 | 139,333 | 137,596 |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 732 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 70 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2016 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 157,943 | 157,516 | 153,937 | 150,216 |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 2,372 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 73 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2017 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 175,939 | 176,728 | 166,690 |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 4,884 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 79 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2018 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 183,358 | 186,580 |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 10,675 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 80 |  |  |  |  |  |  |  |  |
Personal Automobile [Member] | 2019 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 161,056 |  |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 28,339 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 66 |  |  |  |  |  |  |  |  |
Homeowners [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 656,708 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2010 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 60,641 | 60,624 | 60,542 | 60,443 | 60,440 | 60,355 | 59,972 | 60,248 | 60,729 | 60,315
Cumulative Number of Reported Claims | Claims | 25 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2011 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 70,682 | 70,642 | 70,479 | 70,351 | 70,297 | 70,381 | 70,436 | 70,461 | 71,256 |
Cumulative Number of Reported Claims | Claims | 27 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2012 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 54,537 | 54,523 | 54,381 | 54,281 | 54,351 | 54,468 | 54,794 | 53,962 |  |
Cumulative Number of Reported Claims | Claims | 19 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2013 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 51,008 | 50,971 | 50,988 | 50,874 | 51,122 | 51,121 | 50,887 |  |  |
Cumulative Number of Reported Claims | Claims | 13 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2014 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 57,402 | 57,288 | 57,332 | 57,680 | 58,378 | 56,916 |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ (4) |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 18 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2015 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 63,099 | 63,071 | 63,053 | 63,925 | 63,359 |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 45 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 14 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2016 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 63,355 | 63,735 | 64,064 | 62,443 |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 78 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 13 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2017 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 79,305 | 79,911 | 79,283 |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 724 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 18 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2018 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 83,385 | 81,965 |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 1,657 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 19 |  |  |  |  |  |  |  |  |
Homeowners [Member] | 2019 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 73,294 |  |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 6,775 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 14 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 528,544 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2010 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | 21,768 | 21,726 | 21,713 | 21,746 | 21,756 | 21,490 | 21,477 | 20,695 | 19,913 | 19,315
Total IBNR Plus Expected Development on Reported Claims | $ 9 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 7 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2011 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 29,542 | 29,751 | 29,487 | 29,107 | 29,112 | 28,893 | 28,570 | 27,157 | 26,642 |
Total IBNR Plus Expected Development on Reported Claims | $ 18 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 9 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2012 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 31,896 | 31,803 | 31,648 | 31,278 | 31,435 | 30,606 | 27,720 | 26,557 |  |
Total IBNR Plus Expected Development on Reported Claims | $ 28 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 8 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2013 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 36,569 | 36,435 | 36,404 | 35,240 | 34,751 | 33,749 | 32,902 |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 89 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 9 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2014 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 49,168 | 49,284 | 48,213 | 47,326 | 44,544 | 42,760 |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 270 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 11 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2015 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 54,517 | 54,259 | 51,412 | 48,323 | 46,526 |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 662 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 12 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2016 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 67,127 | 65,905 | 57,353 | 54,302 |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 2,134 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 13 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2017 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 67,697 | 67,927 | 61,484 |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 5,149 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 14 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2018 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 81,396 | 79,307 |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 11,763 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 15 |  |  |  |  |  |  |  |  |
Commercial Automobile [Member] | 2019 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 88,864 |  |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 27,764 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 15 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 485,580 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2010 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 30,105 | 29,925 | 29,779 | 29,463 | 29,453 | 29,373 | 29,169 | 29,390 | 29,656 | 28,745
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2011 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 38,434 | 38,160 | 38,105 | 38,270 | 37,385 | 37,576 | 35,942 | 35,411 | 33,054 |
Cumulative Number of Reported Claims | Claims | 7 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2012 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 36,876 | 36,525 | 36,214 | 35,755 | 34,117 | 32,449 | 30,716 | 29,789 |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2013 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 37,453 | 37,365 | 37,981 | 37,205 | 37,292 | 35,679 | 35,683 |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 38 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2014 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 53,116 | 53,294 | 52,336 | 51,843 | 50,135 | 48,204 |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 147 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 7 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2015 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 45,873 | 45,104 | 44,728 | 43,874 | 42,070 |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 519 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2016 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 48,871 | 48,267 | 46,988 | 43,005 |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 2,015 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2017 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 56,517 | 56,043 | 56,185 |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 4,604 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 7 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2018 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 66,470 | 66,265 |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 10,568 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 7 |  |  |  |  |  |  |  |  |
Commercial MultiPeril [Member] | 2019 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 71,865 |  |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 21,633 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 445,090 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2010 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | 26,829 | 26,801 | 26,984 | 27,037 | 27,121 | 26,944 | 26,637 | 27,010 | 27,859 | $ 27,304
Total IBNR Plus Expected Development on Reported Claims | $ 37 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 5 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2011 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 35,034 | 34,926 | 35,194 | 35,039 | 35,670 | 36,369 | 36,614 | 35,757 | $ 32,490 |
Total IBNR Plus Expected Development on Reported Claims | $ 53 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2012 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 35,932 | 35,954 | 36,468 | 37,163 | 37,926 | 38,827 | 39,516 | $ 39,142 |  |
Total IBNR Plus Expected Development on Reported Claims | $ 75 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2013 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 42,651 | 42,555 | 42,327 | 42,828 | 44,289 | 47,027 | $ 46,325 |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 187 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2014 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 47,693 | 47,540 | 48,537 | 49,288 | 51,553 | $ 51,508 |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 264 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2015 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 43,006 | 44,986 | 45,991 | 49,615 | $ 53,332 |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 836 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2016 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 44,969 | 47,883 | 49,802 | $ 58,814 |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 1,630 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2017 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 52,687 | 56,351 | $ 60,450 |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 3,362 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2018 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 55,291 | $ 62,197 |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 7,081 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |
Workers Compensation [Member] | 2019 [Member] |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance | $ 60,998 |  |  |  |  |  |  |  |  |
Total IBNR Plus Expected Development on Reported Claims | $ 19,280 |  |  |  |  |  |  |  |  |
Cumulative Number of Reported Claims | Claims | 6 |  |  |  |  |  |  |  |  |

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