Note 9 - Income Taxes (Details Textual) - CVD Tantaline ApS [Member] - Foreign Tax Authority [Member] - DENMARK - The Danish Ministry of Taxation [Member]	Jun. 30, 2018 USD ($)
Deferred Tax Assets, Valuation Allowance, Total	$ 277,000
Effective Income Tax Rate Reconciliation, at Foreign Statutory Income Tax Rate, Percent	22.00%
Deferred Tax Assets, Gross, Total	$ 277,000

Percentage of foreign statutory tax rate applicable to pretax income (loss).

No definition available.

Name:	cvv_EffectiveIncomeTaxRateReconciliationAtForeignStatutoryIncomeTaxRatePercent
Namespace Prefix:	cvv_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

+ Details

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

- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

+ Details

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

- Details

Name:	srt_ConsolidatedEntitiesAxis=cvv_CVDTantalineApSMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_ForeignCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_DK
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=cvv_TheDanishMinistryOfTaxationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: