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Concentration of Operations - Net Premiums Earned for the Top Ten States (Detail) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
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Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned | $ 88,837 | $ 85,184 | $ 88,995 | $ 87,310 | $ 87,377 | $ 85,118 | $ 82,749 | $ 90,912 | $ 350,326 | $ 346,156 | $ 368,704
Premium earned percentage |  |  |  |  |  |  |  |  | 100.00% | 100.00% | 100.00%
Georgia [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 40,351 | $ 40,801 | $ 38,168
Premium earned percentage |  |  |  |  |  |  |  |  | 11.50% | 11.80% | 10.40%
Florida [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 39,672 | $ 34,615 | $ 29,051
Premium earned percentage |  |  |  |  |  |  |  |  | 11.30% | 10.00% | 7.90%
Pennsylvania [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 31,708 | $ 32,931 | $ 39,460
Premium earned percentage |  |  |  |  |  |  |  |  | 9.10% | 9.50% | 10.70%
Louisiana [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 25,810 | $ 25,422 | $ 30,426
Premium earned percentage |  |  |  |  |  |  |  |  | 7.40% | 7.30% | 8.30%
Illinois [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 19,710 | $ 22,169 | $ 25,796
Premium earned percentage |  |  |  |  |  |  |  |  | 5.60% | 6.40% | 7.00%
North Carolina [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 19,537 | $ 18,388 | $ 20,784
Premium earned percentage |  |  |  |  |  |  |  |  | 5.60% | 5.30% | 5.60%
Virginia [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 15,228 | $ 16,298 | $ 16,599
Premium earned percentage |  |  |  |  |  |  |  |  | 4.30% | 4.70% | 4.50%
Minnesota [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 12,900 | $ 13,968 | $ 15,130
Premium earned percentage |  |  |  |  |  |  |  |  | 3.70% | 4.00% | 4.10%
Wisconsin [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 14,101 | $ 13,790 | $ 13,544
Premium earned percentage |  |  |  |  |  |  |  |  | 4.00% | 4.00% | 3.70%
South Carolina [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 13,924 | $ 13,327 | $ 13,897
Premium earned percentage |  |  |  |  |  |  |  |  | 4.00% | 3.90% | 3.80%
All Others [Member] |  |  |  |  |  |  |  |  |  |  |
Schedule Of Premiums Earned Net By Segment [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net premiums earned |  |  |  |  |  |  |  |  | $ 117,385 | $ 114,447 | $ 125,849
Premium earned percentage |  |  |  |  |  |  |  |  | 33.50% | 33.10% | 34.00%

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- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(1)) -URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17(Column E)) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(13)(c)) -URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
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