v3.8.0.1
Liability for Unpaid Claims and Claim Adjustment Expenses - Summary of Incurred and Paid Claims Development as Supplementary Information - Auto Liability (Detail)
$ in Thousands
Dec. 31, 2017
USD ($)
Claims
Claims Development [Line Items]  
Liabilities for claims and claim adjustment expenses, net of reinsurance $ 893,557
Auto Liability [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 2,452,082
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance 2,059,281
All outstanding liabilities before 2008, net of reinsurance 736 [1]
Liabilities for claims and claim adjustment expenses, net of reinsurance 393,537
Auto Liability [Member] | Accident Year 2008 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period One 280,131 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Two 271,759 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 261,683 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 261,555 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 260,015 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 257,097 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 257,915 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 256,158 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 255,600 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 255,305
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 83
Cumulative Number of Reported Claims | Claims 47,791
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period One $ 92,395 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Two 163,228 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 203,708 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 228,898 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 244,749 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 249,953 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 251,924 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 253,145 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 255,118 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 255,123
Auto Liability [Member] | Accident Year 2009 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Two 299,753 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 273,551 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 263,269 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 258,749 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 260,029 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 258,200 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 257,678 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 256,586 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 256,407
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 104
Cumulative Number of Reported Claims | Claims 47,066
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Two $ 95,847 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 166,441 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 203,869 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 228,650 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 242,768 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 250,681 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 253,417 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 254,988 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 255,308
Auto Liability [Member] | Accident Year 2010 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three 288,166 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 270,935 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 266,223 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 265,949 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 264,104 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 263,040 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 261,930 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 261,092
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 294
Cumulative Number of Reported Claims | Claims 47,089
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Three $ 92,589 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 164,298 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 208,531 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 237,540 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 250,647 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 257,021 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 259,173 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 259,966
Auto Liability [Member] | Accident Year 2011 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four 263,411 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 250,659 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 248,865 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 244,519 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 244,436 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 242,619 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 241,711
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 780
Cumulative Number of Reported Claims | Claims 47,063
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Four $ 93,245 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 161,387 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 197,326 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 217,640 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 230,585 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 236,187 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 238,510
Auto Liability [Member] | Accident Year 2012 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five 251,593 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 242,255 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 231,312 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 228,013 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 229,426 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 228,559
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 1,437
Cumulative Number of Reported Claims | Claims 44,635
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Five $ 82,531 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 150,323 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 183,448 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 204,980 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 214,467 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 219,170
Auto Liability [Member] | Accident Year 2013 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six 242,364 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 236,432 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 233,068 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 231,301 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 228,285
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 3,028
Cumulative Number of Reported Claims | Claims 38,698
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Six $ 79,358 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 143,709 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 181,535 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 204,480 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 215,280
Auto Liability [Member] | Accident Year 2014 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven 232,146 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 223,386 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 217,819 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 215,419
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 6,136
Cumulative Number of Reported Claims | Claims 35,933
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Seven $ 72,838 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 134,376 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 166,947 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 187,375
Auto Liability [Member] | Accident Year 2015 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight 237,578 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 240,697 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 239,421 [1]
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 15,753
Cumulative Number of Reported Claims | Claims 35,921
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Eight $ 78,861 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 149,366 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 186,281
Auto Liability [Member] | Accident Year 2016 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine 259,177 [1]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 256,080 [1]
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 34,429
Cumulative Number of Reported Claims | Claims 36,576
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Nine $ 86,492 [1]
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 153,911
Auto Liability [Member] | Accident Year 2017 [Member]  
Claims Development [Line Items]  
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten 269,803 [1]
Total of Incurred-but- Not-Reported Liabilities Plus Expected Development on Reported Claims $ 77,883
Cumulative Number of Reported Claims | Claims 35,735
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Period Ten $ 88,357
[1] Unaudited supplemental information