v3.26.1
Cover - shares
 6 Months Ended
Mar. 31, 2026
May 11, 2026
Document Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Fiscal Year Focus 2026  
Document Period End Date Mar. 31, 2026  
Document Quarterly Report true  
Document Transition Report false  
Document Fiscal Period Focus Q2  
Entity Registrant Name Armada Acquisition Corp. II  
Entity Central Index Key 0002044009  
Entity Tax Identification Number 98-1815892  
Current Fiscal Year End Date --12-31  
Entity Incorporation, State or Country Code E9  
Entity File Number 001-42661  
Entity Shell Company true  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Address, Address Line One 382 NE 191st Street  
Entity Address, Address Line Two Suite 52895  
Entity Address, City or Town Miami  
Entity Address, State or Province FL  
Entity Address, Postal Zip Code 33179-52895  
City Area Code 215  
Local Phone Number 543-6886  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Ex Transition Period false  
Units Each Consisting Of One Share Of Common Stock And Onehalf Of One Redeemable Warrant [Member]    
Document Information [Line Items]    
Title of 12(b) Security Units, each consisting of one share of Class A ordinary share one half of one redeemable warrant  
Trading Symbol XRPNU  
Security Exchange Name NASDAQ  
Common Stock Par Value0.0001 Per Share [Member]    
Document Information [Line Items]    
Title of 12(b) Security Class A ordinary share, par value $0.0001 per share  
Trading Symbol XRPN  
Security Exchange Name NASDAQ  
Warrants Each Exercisable For One Share Of Common Stock For11.50 Per Share [Member]    
Document Information [Line Items]    
Title of 12(b) Security Warrants, exercisable for one Class A ordinary share for $11.50 per share  
Trading Symbol XRPNW  
Security Exchange Name NASDAQ  
Common Class A [Member]    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   23,710,000
Common Class B [Member]    
Document Information [Line Items]    
Entity Common Stock, Shares Outstanding   7,880,000