v3.25.1
Document and Entity Information - shares
6 Months Ended
Mar. 31, 2025
Apr. 28, 2025
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2025  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q2  
Current Fiscal Year End Date --09-30  
Document Quarterly Report true  
Document Transition Report false  
Entity Central Index Key 0001748945  
Securities Act File Number 000-56435  
Entity Registrant Name Grayscale Horizen Trust (ZEN)  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 83-6217411  
Entity Address, Address Line One c/o Grayscale Investments Sponsors, LLC  
Entity Address, Address Line Two 290 Harbor Drive, 4th Floor  
Entity Address, City or Town Stamford  
Entity Address, State or Province CT  
Entity Address, Postal Zip Code 06902  
City Area Code 212  
Local Phone Number 668-1427  
Title of 12(g) Security Grayscale Horizen Trust (ZEN) Shares  
Trading Symbol HZEN  
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 true  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   11,425,100