Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023
Statement of Stockholders' Equity [Abstract]
Issuance costs	$ 45,554	$ 2,495

Common stock and pre-funded warrants issuance costs.

No definition available.

Name:	janx_CommonStockAndPreFundedWarrantsIssuanceCosts
Namespace Prefix:	janx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration