v3.26.1
Cover - USD ($)
 12 Months Ended
Dec. 31, 2025
Mar. 27, 2026
Jun. 30, 2025
Document Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Transition Report false    
Document Financial Statement Error Correction [Flag] false    
Entity Interactive Data Current Yes    
ICFR Auditor Attestation Flag false    
Amendment Flag false    
Document Period End Date Dec. 31, 2025    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Entity Registrant Name JENA ACQUISITION CORPORATION II    
Entity Central Index Key 0002060337    
Entity File Number 001-42674    
Entity Tax Identification Number 98-1842831    
Entity Incorporation, State or Country Code E9    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Shell Company true    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company true    
Entity Ex Transition Period false    
Entity Public Float     $ 236,440,000
Entity Address, Address Line One 1701 Village Center Circle    
Entity Address, City or Town Las Vegas    
Entity Address, State or Province NV    
Entity Address, Postal Zip Code 89134    
City Area Code (702)    
Local Phone Number 323-7330    
Units, each consisting of one Class A ordinary share and one right      
Document Information [Line Items]      
Title of 12(b) Security Units, each consisting of one Class A Ordinary Share and one Right    
Trading Symbol JENA.U    
Security Exchange Name NYSE    
Class A ordinary shares, par value $0.0001 per share      
Document Information [Line Items]      
Title of 12(b) Security Class A Ordinary Shares, par value $0.0001 per share    
Trading Symbol JENA    
Security Exchange Name NYSE    
Rights, each entitling the holder to receive one-twentieth (1/20) of one Class A Ordinary Share      
Document Information [Line Items]      
Title of 12(b) Security Rights, each entitling the holder to receive one-twentieth (1/20) of one Class A Ordinary Share    
Trading Symbol JENA.R    
Security Exchange Name NYSE    
Class A Ordinary Shares      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   23,225,000  
Class B Ordinary Shares      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   5,750,000