v3.25.2
Cover - shares
 6 Months Ended
Jun. 30, 2025
Aug. 01, 2025
Document Information [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Entity Interactive Data Current Yes  
Amendment Flag false  
Document Period End Date Jun. 30, 2025  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Entity Information [Line Items]    
Entity Registrant Name HELIX ACQUISITION CORP. II  
Entity Central Index Key 0001869105  
Entity File Number 001-41955  
Entity Tax Identification Number 00-0000000  
Entity Incorporation, State or Country Code E9  
Current Fiscal Year End Date --12-31  
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 Incorporation, Date of Incorporation Jun. 15, 2021  
Entity Contact Personnel [Line Items]    
Entity Address, Address Line One 200 Clarendon Street  
Entity Address, Address Line Two 52nd Floor  
Entity Address, City or Town Boston  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02116  
Entity Phone Fax Numbers [Line Items]    
City Area Code (857)  
Local Phone Number 702-0370  
Entity Listings [Line Items]    
Title of 12(b) Security Class A ordinary share, par value $0.0001 per share  
Trading Symbol HLXB  
Security Exchange Name NASDAQ  
Class A Ordinary Shares    
Entity Listings [Line Items]    
Entity Common Stock, Shares Outstanding   18,909,000
Class B Ordinary Shares    
Entity Listings [Line Items]    
Entity Common Stock, Shares Outstanding   4,600,000