Note 5 - Fair Value of Financial Instruments (Details Textual) xbrli-pure in Thousands	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)
Debt Securities, Available-for-sale, Total	$ 77,648,829	$ 77,554,999
Number of Other-than-temporarily Impaired Available-for-sale Securities	0
Number of Other-than-temporarily Impaired Marketable Securities	0
Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure	$ 0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0
Corporate Bond Securities [Member]
Debt Securities, Available-for-sale, Total	69,482,404	$ 73,603,967
Corporate Bond Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	$ 51,558,274

Represents number of other-than-temporarily impaired available-for-sale securities.

No definition available.

Name:	nvec_NumberOfOtherThanTemporarilyImpairedAvailableForsaleSecurities
Namespace Prefix:	nvec_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of marketable securities the company considers other-than-temporarily impaired.

+ References

No definition available.

+ Details

Name:	nvec_NumberOfOtherThanTemporarilyImpairedMarketableSecurities
Namespace Prefix:	nvec_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of financial and nonfinancial obligations.

+ References

+ Details

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

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: