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%

Subsidiary Disclosure on Geographic Areas Revenue from External Customers Attributed To Foreign Countries As Percent Of Total Foreign Sales

No definition available.

Name:	naii_SubsidiaryDisclosureOnGeographicAreasRevenueFromExternalCustomersAttributedToForeignCountriesAsPercentOfTotalForeignSales
Namespace Prefix:	naii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration