Note 12 - Subsequent Event (Details Textual) - USD ($)	Oct. 01, 2021	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Forecast [Member] \| HSBC Bank [Member]
Mortgage Modification Agreement, Requirement, Minimum Liquid Assets	$ 4,000,000	$ 4,000,000	$ 3,750,000	$ 3,500,000	$ 3,250,000	$ 3,000,000

The minimum liquid assets required to maintain pursuant to the mortgage modification agreement.

No definition available.

Name:	cvv_MortgageModificationAgreementRequirementMinimumLiquidAssets
Namespace Prefix:	cvv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant