Marketable Securities - Additional Information (Detail) - USD ($)	Jul. 31, 2024	Apr. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Allowance for credit losses on securities in unrealized loss position recognized	$ 0	$ 0

Allowance for credit losses on securities in unrealized loss position recognized.

No definition available.

Name:	kalv_AllowanceForCreditLossesOnSecuritiesInUnrealizedLossPositionRecognized
Namespace Prefix:	kalv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant