Subsequent Events (Narratives) (Details) $ in Millions	Dec. 01, 2018 USD ($)
Subsequent Events [Abstract]
Reinsurance agreement termination cash transfer	$ 64.6

Amount of net cash transferred that supported net liabilities, less transaction offsets for terminated reinsurance agreement with third party company.

No definition available.

Name:	uhal_ReinsuranceAgreementTerminationCashTransfer
Namespace Prefix:	uhal_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant