Document and Entity Information (USD $)	12 Months Ended
	Mar. 31, 2013	Sep. 30, 2012
Document and Entity Information [Abstract]
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	No
Entity Public Float		$ 510,020,982
Document Fiscal Year Focus	2013
Document Type	10-K
Document Fiscal Period Focus	FY
Document Period End Date	Mar. 31, 2013
Amendment Flag	true
Amendment Description	To file XBRL files
Entity Common Stock, Shares Outstanding	19,607,788