Income Taxes - Schedule of Company's Deferred Income Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred income tax assets:
Discounting of net unpaid loss and loss adjustment expenses	$ 17,493	$ 21,878
Unearned premiums	14,008	12,043
Accrued expenses and other	4,336	3,870
Accrued policyholder dividends	684	916
Impaired securities	874	94
Accrued insurance-related assessments	3,989	3,564
AMT tax credit		64
Total deferred tax assets	41,384	42,429
Deferred income tax liabilities:
Deferred policy acquisition costs and deferred charges	(7,937)	(8,165)
Unrealized gain (loss) on securities available-for-sale	2,313	(1,604)
Property and equipment and other	(266)	(356)
Salvage and subrogation	(288)	(442)
Guaranty fund related items	(1,561)	(2,341)
Total deferred income tax liabilities	(7,739)	(12,908)
Net deferred income taxes	$ 33,645	$ 29,521