Subsequent Events - Additional Information (Detail) (New Contract, Cash Flow Hedging, EUR €) In Millions, unless otherwise specified	1 Months Ended
Sep. 07, 2012
Number of purchased forward contracts	15
Forward contracts, notional amount	5.3
Forward contracts, weighted average forward rate	1.28
Minimum
Forward contracts expiration, year and month	2012-12
Maximum
Forward contracts expiration, year and month	2014-02

Monetary amount specified by the derivative(s). Expressed as an absolute value.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

+ Details

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Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Derivative, Maturity Month and Year

+ References

No definition available.

+ Details

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Namespace Prefix:	naii_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

The average contractual rate at which a foreign currency can be purchased or sold under the terms of a group of foreign currency derivative contracts.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5580258-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5579245-113959

+ Details

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