v3.7.0.1
Liability for Unpaid Claims and Claim Adjustment Expenses - Summary of Incurred and Paid Claims Development as Supplementary Information - Commercial Multi-Peril (Detail)
$ in Thousands
Dec. 31, 2016
USD ($)
Claims
Claims Development [Line Items]  
Liabilities for claims and claim adjustment expenses, net of reinsurance $ 850,035
Commercial Multi-Peril [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 338,266
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 255,770
All outstanding liabilities before 2007, net of reinsurance 5,763 [1]
Liabilities for claims and claim adjustment expenses, net of reinsurance 88,259
Commercial Multi-Peril [Member] | Accident Year 2007 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period One 43,834 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Two 40,324 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 39,877 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 39,215 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 39,309 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 38,158 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 38,218 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 38,078 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 38,243 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 37,861
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 684
Cumulative Number of Reported Claims | Claims 3,290
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period One $ 11,548 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Two 17,625 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 21,869 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 26,682 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 31,080 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 34,386 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 35,217 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 35,738 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 36,054 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 36,474
Commercial Multi-Peril [Member] | Accident Year 2008 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Two 40,640 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 39,231 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 37,105 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 37,825 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 37,034 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 35,594 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 36,141 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 37,605 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 37,298
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 1,061
Cumulative Number of Reported Claims | Claims 3,831
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Two $ 10,083 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 17,357 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 20,638 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 25,415 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 29,900 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 32,187 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 34,321 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 34,847 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 35,270
Commercial Multi-Peril [Member] | Accident Year 2009 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 41,027 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 38,666 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 36,610 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 35,354 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 34,884 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 34,381 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 34,529 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 34,079
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 989
Cumulative Number of Reported Claims | Claims 3,512
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three $ 11,101 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 17,248 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 21,660 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 25,779 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 30,272 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 32,150 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 32,623 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 32,842
Commercial Multi-Peril [Member] | Accident Year 2010 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 41,116 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 37,736 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 40,243 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 37,520 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 35,914 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 37,839 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 37,215
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 1,294
Cumulative Number of Reported Claims | Claims 3,583
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four $ 12,511 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 17,490 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 22,135 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 27,152 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 31,378 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 33,384 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 34,888
Commercial Multi-Peril [Member] | Accident Year 2011 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 42,185 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 40,825 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 39,037 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 38,160 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 38,456 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 36,945
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 1,308
Cumulative Number of Reported Claims | Claims 3,552
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five $ 13,092 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 18,390 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 22,616 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 28,291 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 30,458 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 32,692
Commercial Multi-Peril [Member] | Accident Year 2012 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 35,169 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 28,548 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 26,805 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 23,258 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 23,385
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 1,206
Cumulative Number of Reported Claims | Claims 2,704
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six $ 11,525 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 14,454 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 16,263 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 18,670 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 20,716
Commercial Multi-Peril [Member] | Accident Year 2013 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 33,979 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 27,592 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 27,867 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 26,970
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 2,653
Cumulative Number of Reported Claims | Claims 2,188
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven $ 9,374 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 12,723 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 15,426 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 18,406
Commercial Multi-Peril [Member] | Accident Year 2014 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 36,852 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 31,220 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 34,911
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 4,962
Cumulative Number of Reported Claims | Claims 2,229
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight $ 12,001 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 16,484 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 20,199
Commercial Multi-Peril [Member] | Accident Year 2015 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 33,997 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 31,488
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 9,814
Cumulative Number of Reported Claims | Claims 2,003
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine $ 9,820 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 12,956
Commercial Multi-Peril [Member] | Accident Year 2016 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 38,114
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 20,761
Cumulative Number of Reported Claims | Claims 3,069
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten $ 11,327
[1] Unaudited supplemental information