Name:	nssc_CommitmentAnnualSalary
Namespace Prefix:	nssc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The rate applied to the most recent 5-year average of annual salaries, as defined, to calculate termination pay the entity has committed to pay under specified circumstances.

No definition available.

Name:	nssc_CommitmentTerminationPay
Namespace Prefix:	nssc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The year in which an agreement expires.

No definition available.

Name:	nssc_ExpirationYear
Namespace Prefix:	nssc_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

As of the reporting date, the annual amount of minimum rent the entity is obligated to pay under the terms of an operating lease.

No definition available.

Name:	nssc_OperatingLeaseCommitmentAnnualRent
Namespace Prefix:	nssc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

Name:	us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41499-112717

Name:	us-gaap_OperatingLeasesRentExpenseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Name:	us-gaap_OtherCommitmentsAxis=us-gaap_EmploymentContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_ChiefExecutiveOfficerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=nssc_SeniorVicePresidentOfSalesAndMarketingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=nssc_SeniorVicePresidentOfEngineeringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_MajorPropertyClassAxis=nssc_LandBelowForeignProductionFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: