XML 53 R33.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Defined Benefit Pension Plan - Additional Information (Detail) | Sep. 30, 2013
--- | ---
Defined Benefit Plan Disclosure [Line Items] |
Years prior to retirement used to determine employee benefit under defined benefit pension plan | 5 years

X
- Definition The period of service used in calculating an employee's benefit under a defined benefit pension plan. + References No definition available. + Details
Name: | naii_NumberOfYearsCompensationUsedForBenefitObligationAssumptions
Namespace Prefix: | naii_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

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