Document and Entity Information - shares	3 Months Ended	9 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Nov. 01, 2020
Document and Entity Information [Abstract]
Entity Registrant Name		AMERCO
Entity Central Index Key	0000004457
Entity Current Reporting Status		Yes
Entity Small Business	false
Current Fiscal Year End Date	--03-31
Entity Filer Category		Large Accelerated Filer
Entity Emerging Growth Company	false
Document Fiscal Year Focus	2021
Trading Symbol		UHAL
Document Type		10-Q
Document Fiscal Period Focus	Q3
Document Period End Date	Dec. 31, 2020
Amendment Flag	false
Entity Common Stock, Shares Outstanding			19,607,788
Entity Shell Company	false
Entity Interactive Data Current		Yes
Entity File Number	001-11255
Entity Tax Identification Number		88-0106815
Entity address, address line one		5555 Kietzke Lane
Entity address, address line two		Suite 100
Entity address, City or Town		Reno
Entity address, State or Province		NV
Entity address, postal zip code	89511
City Area Code		( 775
Local Phone Number		688-6300
Entity Incorporation, State or Country Code		NV
Title of 12(b) Security		Common Stock
Security Exchange Name		NASDAQ
Document Quarterly Report	true
Document Transition Report	false