Concentration of Operations - Net Premiums Earned for the Top Ten States (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned	$ 92,097	$ 89,918	$ 90,728	$ 95,961	$ 95,034	$ 90,504	$ 95,569	$ 94,787	$ 368,704	$ 375,894	$ 375,747
Premium earned percentage									100.00%	100.00%	100.00%
Pennsylvania [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 39,460	$ 36,294	$ 35,488
Premium earned percentage									10.70%	9.70%	9.40%
Georgia [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 38,168	$ 40,497	$ 36,761
Premium earned percentage									10.40%	10.80%	9.80%
Louisiana [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 30,426	$ 38,874	$ 47,643
Premium earned percentage									8.30%	10.30%	12.70%
Florida [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 29,051	$ 24,792	$ 20,691
Premium earned percentage									7.90%	6.60%	5.50%
Illinois [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 25,796	$ 23,285	$ 20,606
Premium earned percentage									7.00%	6.20%	5.50%
North Carolina [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 20,784	$ 20,062	$ 20,872
Premium earned percentage									5.60%	5.30%	5.60%
Virginia [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 16,599	$ 15,656	$ 16,764
Premium earned percentage									4.50%	4.20%	4.50%
Minnesota [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 15,130	$ 14,618	$ 13,159
Premium earned percentage									4.10%	3.90%	3.50%
South Carolina [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 13,897	$ 12,955	$ 12,414
Premium earned percentage									3.80%	3.40%	3.30%
Wisconsin [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 13,544	$ 11,203	$ 9,408
Premium earned percentage									3.70%	3.00%	2.50%
All Others [Member]
Schedule Of Premiums Earned Net By Segment [Line Items]
Net premiums earned									$ 125,849	$ 137,658	$ 141,941
Premium earned percentage									34.00%	36.60%	37.70%