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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