Income Taxes (Deferred Tax Assets and Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
General expenses	$ 1,415nsec_DeferredTaxAssetGeneralExpenses	$ 1,371nsec_DeferredTaxAssetGeneralExpenses
Unearned premiums	2,009nsec_DeferredTaxAssetUnearnedPremiums	1,961nsec_DeferredTaxAssetUnearnedPremiums
Claims liabilities	863	849
Litigation settlement	2,040	2,040
AMT Credit	1,121nsec_DeferredTaxAssetAmtCredit	1,240nsec_DeferredTaxAssetAmtCredit
Impairment on real estate owned	187	187
Unrealized loss on interest rate swaps	482	421
Deferred tax assets	8,117us-gaap_DeferredTaxAssetsGross	8,069us-gaap_DeferredTaxAssetsGross
Depreciation	(107)	(111)
Deferred policy acquisition costs	(2,919)	(2,921)
Unrealized gains on securities available-for-sale	(2,036)	(1,848)
Deferred tax liabilities	(5,062)us-gaap_DeferredIncomeTaxLiabilities	(4,880)us-gaap_DeferredIncomeTaxLiabilities
Net deferred tax asset	$ 3,055nsec_NetDeferredTaxAssetsLiabilities	$ 3,189nsec_NetDeferredTaxAssetsLiabilities

Deferred Tax Asset, AMT Credit

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- Definition

Gross deferred tax asset associated with general expenses.

+ References

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- Definition

Deferred Tax Asset, Real Estate Impairment

+ References

No definition available.

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- Definition

Deferred tax asset related to litigation settlement.

+ References

No definition available.

+ Details

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- Definition

Deferred tax asset associated with unearned premiums.

+ References

No definition available.

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- Definition

Deferred tax asset on unrealized loss on interest rate swaps.

+ References

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- Definition

Net Deferred Tax Assets (Liabilities)

+ References

No definition available.

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- Definition

Amount of deferred tax liability attributable to taxable temporary differences.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Deferred Tax Liability

-URI http://asc.fasb.org/extlink&oid=6510232

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph b(2)

-Article 7

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Name Accounting Standards Codification

-Glossary Deferred Tax Asset

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

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-Section 25

-Paragraph 20

-Subparagraph (d)

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

-Paragraph 6

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- Definition

Amount of deferred tax liability attributable to taxable temporary differences from investments (excludes investments in subsidiaries and equity method investments).

+ References

No definition available.

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- Definition

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

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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