Document and Entity Information - shares	9 Months Ended
	Jun. 30, 2022	Aug. 01, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--09-30
Document Quarterly Report	true
Document Transition Report	false
Entity Central Index Key	0001748945
Entity 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, 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	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		6,838,000