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Segment Information - Additional Information (Detail) | 12 Months Ended
--- | ---
Jun. 30, 2012 Segment | Jun. 30, 2011
Segment Reporting Information [Line Items] |  |
Number of segments | 3 |
Percentage of net sales for products manufactured by NAIE in markets outside U.S | 67.00% | 66.00%

X
- Definition Number of Reportable Segments + References No definition available. + Details
Name: | naii_NumberOfReportableSegments
Namespace Prefix: | naii_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Subsidiary Disclosure on Geographic Areas Revenue from External Customers Attributed To Foreign Countries As Percent Of Total Foreign Sales + References No definition available. + Details
Name: | naii_SubsidiaryDisclosureOnGeographicAreasRevenueFromExternalCustomersAttributedToForeignCountriesAsPercentOfTotalForeignSales
Namespace Prefix: | naii_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration