Note F - Debt (Details Textual) - USD ($)		3 Months Ended
Jul. 01, 2019	Dec. 31, 2019
Proceeds from Long-term Lines of Credit		$ 0
Line of Credit Facility, Remaining Borrowing Capacity		$ 10,000,000
Wells Fargo Bank, N.A. [Member] \| Credit Agreement [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 10,000,000
Long-term Debt, Percentage Bearing Fluctuating Interest, Threshold Amount	100,000
Minimum Prepayment Amount Under Line of Credit	$ 100,000
Wells Fargo Bank, N.A. [Member] \| Credit Agreement [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	1.25%
Debt Instrument Basis Spread on Elected Fixed Rate Borrowing	1.25%
Wells Fargo Bank, N.A. [Member] \| Credit Agreement [Member] \| Maximum [Member]
Ratio of Indebtedness to Net Capital	1.25
Ratio of Total Current Assets to Total Current Liabilities	1.75

The percentage points added to the reference rate to compute fixed rate elections on the debt instrument.

No definition available.

Name:	naii_DebtInstrumentBasisSpreadOnElectedFixedRateBorrowing
Namespace Prefix:	naii_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a fluctuating rate when amount is less than threshold.

+ References

No definition available.

+ Details

Name:	naii_LongTermDebtPercentageBearingFluctuatingInterestThresholdAmount
Namespace Prefix:	naii_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The minimum payment amount that may be prepaid on a line of credit facility with a fixed interest rate.

+ References

No definition available.

+ Details

Name:	naii_MinimumPrepaymentAmountUnderLineOfCredit
Namespace Prefix:	naii_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Total current assets divided by total current liabilities.

+ References

No definition available.

+ Details

Name:	naii_RatioOfTotalCurrentAssetsToTotalCurrentLiabilities
Namespace Prefix:	naii_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

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

- Definition

Indebtedness divided by net capital.

+ References

No definition available.

+ Details

Name:	us-gaap_RatioOfIndebtednessToNetCapital1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=naii_WellsFargoBankNAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=naii_CreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: