Document and Entity Information - shares	9 Months Ended
	Dec. 31, 2018	Feb. 01, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	AMERCO /NV/
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	2019
Document Type	10-Q
Document Fiscal Period Focus	Q3
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Entity Common Stock, Shares Outstanding		19,607,788