Related Party Transactions - Additional Information (Details)	Mar. 31, 2023
Related Party Transactions [Abstract]
Minimum beneficial ownership percentage of outstanding capital stock	5.00%

Minimum beneficial ownership percentage of outstanding capital stock.

No definition available.

Name:	janx_MinimumBeneficialOwnershipPercentageOfOutstandingCapitalStock
Namespace Prefix:	janx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant