Schedule I - Condensed Financial Information of AMERCO (Narratives) (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Income Taxes Paid, Net [Abstract]
Income taxes paid (net of income tax refunds)	$ 68,671	$ 36,880	$ 141,901

The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4297-108586

Name:	us-gaap_IncomeTaxesPaidNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration