Document and Entity Information - USD ($)	12 Months Ended
	Mar. 31, 2019	May 24, 2019	Sep. 28, 2018
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	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Public Float			$ 3,167,360,502
Document Fiscal Year Focus	2019
Document Type	10-K
Document Fiscal Period Focus	FY
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Entity Common Stock, Shares Outstanding		19,607,788
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false