v3.26.1
Document And Entity Information - shares
 3 Months Ended
Mar. 31, 2026
May 06, 2026
Document Information Line Items    
Entity Central Index Key 0002034334  
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Fiscal Year Focus 2026  
Document Transition Report false  
Entity File Number 1-42521  
Entity Registrant Name ARTIUS II ACQUISITION INC.  
Entity Incorporation, State or Country Code E9  
Entity Tax Identification Number 98-1802901  
Entity Address, Address Line One 3 Columbus Circle  
Entity Address, Address Line Two Suite 1609  
Entity Address, State or Province NY  
Entity Address, City or Town NY  
Entity Address, Postal Zip Code 10019  
City Area Code 212  
Local Phone Number 309-7668  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company true  
Amendment Flag false  
Document Fiscal Period Focus Q1  
Current Fiscal Year End Date --12-31  
Units [Member]    
Document Information Line Items    
Title of 12(b) Security Units, each consisting of one Class A ordinary share, $0.0001 par value, including one attached contingent right, and one right to receive one tenth  
Trading Symbol AACBU  
Security Exchange Name NASDAQ  
Common Class A [Member]    
Document Information Line Items    
Title of 12(b) Security Class A ordinary shares, par value $0.0001 per share, including one attached contingent right  
Trading Symbol AACB  
Security Exchange Name NASDAQ  
Rights [Member]    
Document Information Line Items    
Title of 12(b) Security Rights, each right entitling the holder to receive one tenth of one Class A ordinary share  
Trading Symbol AACBR  
Security Exchange Name NASDAQ  
Class A Ordinary Shares [Member]    
Document Information Line Items    
Entity Common Stock, Shares Outstanding   22,175,000
Class B Ordinary Shares [Member]    
Document Information Line Items    
Entity Common Stock, Shares Outstanding   5,500,000