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Note J - Treasury Stock (Details Textual) (USD $)	9 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Feb. 06, 2015	Jun. 02, 2011	May 11, 2015
Stock Repurchase Program, Authorized Amount			$ 3,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1	$ 2,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1
Treasury Stock, Shares, Acquired	157,539us-gaap_TreasuryStockSharesAcquired	5,100us-gaap_TreasuryStockSharesAcquired
Treasury Stock Acquired, Average Cost Per Share	$ 5.57us-gaap_TreasuryStockAcquiredAverageCostPerShare	$ 4.55us-gaap_TreasuryStockAcquiredAverageCostPerShare
Treasury Stock, Value, Acquired, Cost Method	878,000us-gaap_TreasuryStockValueAcquiredCostMethod	23,000us-gaap_TreasuryStockValueAcquiredCostMethod
2015 Increase [Member] | Subsequent Event [Member]
Stock Repurchase Program, Authorized Amount					2,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_ShareRepurchaseProgramAxis = naii_Increase2015Member / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
2015 Increase [Member]
Stock Repurchase Program, Authorized Amount			1,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_ShareRepurchaseProgramAxis = naii_Increase2015Member
Subsequent Event [Member]
Stock Repurchase Program, Authorized Amount					$ 5,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1 / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember

X

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Total cost of shares repurchased divided by the total number of shares repurchased.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

+ Details

Name:	us-gaap_TreasuryStockAcquiredAverageCostPerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of shares that have been repurchased during the period and are being held in treasury.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

+ Details

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

X

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=naii_Increase2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: