Document and Entity Information (USD $)	12 Months Ended
	Mar. 31, 2012
Document Information [Line Items]
Entity Registrant Name	Amerco /NV/
Entity Central Index Key	0000004457
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--03-31
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Public Float	$ 397,855,149
Document Fiscal Year Focus	2012
Document Type	10-K
Document Fiscal Period Focus	FY
Document Period End Date	Mar. 31, 2012
Amendment Flag	false
Entity Common Stock, Shares Outstanding	19,607,788