Income Taxes - Schedule of Company's Deferred Income Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred income tax assets:
Discounting of net unpaid loss and loss adjustment expenses	$ 17,952	$ 17,493
Unearned premiums	14,788	14,008
Accrued expenses and other	4,306	4,336
State income tax	591us-gaap_DeferredTaxAssetsStateTaxes
Accrued policyholder dividends	438	684
Impaired securities	80	874
Accrued insurance-related assessments	4,804	3,989
Total deferred tax assets	42,959us-gaap_DeferredTaxAssetsGross	41,384us-gaap_DeferredTaxAssetsGross
Deferred income tax liabilities:
Deferred policy acquisition costs	(8,815)	(7,937)
Unrealized gain (loss) on securities available-for-sale	(1,513)	2,313
Property and equipment and other	(331)	(266)
Salvage and subrogation	(289)	(288)
Guaranty fund related items	(780)	(1,561)
Total deferred income tax liabilities	(11,728)us-gaap_DeferredTaxLiabilities	(7,739)us-gaap_DeferredTaxLiabilities
Net deferred income taxes	$ 31,231us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 33,645us-gaap_DeferredTaxAssetsLiabilitiesNet

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards, net of deferred tax liability attributable to taxable temporary differences.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from state taxes.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from loss reserves other than estimated credit losses.

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The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from estimated policyholder reserves, which will be deductible from future taxable income when actual costs are incurred, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the tax deduction to be taken.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from the unearned premiums reserve.

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The amount as of the balance sheet date of the estimated future tax effects attributable to policy acquisition costs being expensed for tax purposes but capitalized in conformity with generally accepted accounting principles, which will reverse in future periods when amortization of such capitalized costs cannot be deducted for tax purposes.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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