v3.25.4
Cover - shares
 9 Months Ended
Dec. 31, 2025
Feb. 06, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Dec. 31, 2025  
Document Transition Report false  
Entity File Number 001-36827  
Entity Registrant Name Anterix Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 33-0745043  
Entity Address, Address Line One 3 Garret Mountain Plaza  
Entity Address, Address Line Two Suite 401  
Entity Address, City or Town Woodland Park  
Entity Address, State or Province NJ  
Entity Address, Postal Zip Code 07424  
City Area Code 973  
Local Phone Number 771-0300  
Title of 12(b) Security Common Stock, $0.0001 par value  
Trading Symbol ATEX  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   18,732,889
Entity Central Index Key 0001304492  
Current Fiscal Year End Date --03-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q3  
Amendment Flag false