Income Taxes - Schedule of Company's Deferred Income Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred income tax assets:
Discounting of net unpaid loss and loss adjustment expenses	$ 16,035	$ 15,415
Unearned premiums	14,483	14,839
Accrued expenses and other	3,640	3,904
State income tax	617	488
Accrued policyholder dividends	2,024	719
Impaired securities	70	238
Capital loss carryforward	15	715
Accrued insurance-related assessments	5,323	4,953
Net unrealized loss on securities	265
Total deferred tax assets	42,472	41,271
Deferred income tax liabilities:
Deferred policy acquisition costs	(8,492)	(9,012)
Callable bond amortization	(10)
Unrealized gain on securities available-for-sale		(1,393)
Property and equipment and other	204	(696)
Salvage and subrogation	(363)	(265)
Total deferred income tax liabilities	(8,661)	(11,366)
Net deferred income taxes	$ 33,811	$ 29,905