Segments (Schedule of Gross and Net Premiums Earned) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Property and Casualty operations premiums earned:
Gross premiums earned	$ 15,093	$ 15,179
Reinsurance premium ceded	(2,159)	(1,683)
Net premiums earned	12,934	13,496
Life Insurance Segment [Member]
Life, accident and health operations premiums earned:
Traditional life insurance	1,316	1,308
Accident and health insurance	449	464
Total life, accident and health	1,765	1,772
Property and Casualty operations premiums earned:
Net premiums earned	1,746	1,752
Consolidated Property and Casualty Insurance Entity [Member]
Property and Casualty operations premiums earned:
Dwelling fire & extended coverage	7,018	6,547
Homeowners (Including mobile homeowners)	5,681	5,904
Ocean marine	256	268
Other liability	373	340
Private passenger auto liability	0	235
Commercial auto liability	0	6
Auto physical damage	0	107
Total property and casualty	13,328	13,407
Net premiums earned	$ 11,188	$ 11,744

Auto Physical Damage Earned Premium

No definition available.

Name:	nsec_AutoPhysicalDamageEarnedPremium
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Premiums assumed and earned by another insurer as a result of reinsurance arrangements.

+ References

No definition available.

+ Details

Name:	nsec_CededEarnedPremium
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Commercial Auto Liability Earned Premium

+ References

No definition available.

+ Details

Name:	nsec_CommercialAutoLiabilityEarnedPremium
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Premiums earned directly for all insurance segments before adding contracts assumed from other insurers or subtracting any amounts assumed by other insurers.

+ References

No definition available.

+ Details

Name:	nsec_DirectPremiumsEarned
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Direct Premiums Earned, Life, Accident and Health

+ References

No definition available.

+ Details

Name:	nsec_DirectPremiumsEarnedLifeAccidentAndHealth
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	nsec_DirectPremiumsEarnedLifeAccidentAndHealthAbstract
Namespace Prefix:	nsec_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	nsec_DirectPremiumsEarnedPropertyAndCasualtyAbstract
Namespace Prefix:	nsec_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Dwelling Fire & Extended Coverage Earned Premium

+ References

No definition available.

+ Details

Name:	nsec_DwellingFireExtendedCoverageEarnedPremium
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Homeowners Earned Premium (including Mobile Homeowners)

+ References

No definition available.

+ Details

Name:	nsec_HomeownersEarnedPremium
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Ocean Marine Earned Premium

+ References

No definition available.

+ Details

Name:	nsec_OceanMarineEarnedPremium
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Other Liability Earned Premium

+ References

No definition available.

+ Details

Name:	nsec_OtherLiabilityEarnedPremium
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Private Passenger Auto Liability Earned Premium

+ References

No definition available.

+ Details

Name:	nsec_PrivatePassengerAutoLiabilityEarnedPremium
Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Premiums earned directly for all accident and health insurance before adding contracts assumed from other insurers or subtracting any amounts assumed by other insurers.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 113

-Paragraph 27

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 605

-Section 50

-Paragraph 1

-Subparagraph (b),(c)(3)

-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

+ Details

Name:	us-gaap_DirectPremiumsEarnedAccidentAndHealth
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Premiums earned directly for all life insurance before adding contracts assumed from other insurers or subtracting any amounts assumed by other insurers.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 605

-Section 50

-Paragraph 1

-Subparagraph (b),(c)(3)

-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 113

-Paragraph 27

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 1

-Article 7

+ Details

Name:	us-gaap_DirectPremiumsEarnedLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Premiums earned directly for all property and casualty insurance before adding contracts assumed from other insurers or subtracting any amounts assumed by other insurers.

+ References

+ Details

Name:	us-gaap_DirectPremiumsEarnedPropertyAndCasualty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Premiums earned on the income statement for all insurance and reinsurance contracts after subtracting any amounts ceded to another insurer and adding premiums assumed from other insurers.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(c))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.1)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 1

-Article 7

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 113

-Paragraph 27

-Subparagraph a, b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_PremiumsEarnedNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration