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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
	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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+ 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

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