INVESTMENTS (Schedule of Unrealized Appreciation) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Investments [Abstract]
Fixed maturities	$ 2,195	$ (3,042)
Deferred income tax	(461)	638
Change in net unrealized gains (losses) on available-for-sale securities	$ 1,734	$ (2,404)

The change in deferred tax associated with the change in unrealized holding gain (loss) on available-for-sale securities included in a separate component of shareholders' equity during the period.

No definition available.

+ Details

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Namespace Prefix:	nsec_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

This item represents the pretax change in net unrealized holding gain (loss) on available-for-sale securities that has been included in accumulated other comprehensive income, a separate component of shareholders' equity, during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

+ Details

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Period Type:	duration

- Definition

The change in unrealized holding gain (loss), net of tax, on available-for-sale securities included in a separate component of shareholders' equity during the period.

+ References

+ Details

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- References

No definition available.

+ Details

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