Document and Entity Information - shares	3 Months Ended
	Jun. 30, 2018	Aug. 01, 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
Document Fiscal Year Focus	2019
Document Type	10-Q
Document Fiscal Period Focus	Q1
Document Period End Date	Jun. 30, 2018
Amendment Flag	false
Entity Common Stock, Shares Outstanding		19,607,788