Contingencies (Narratives) (Details) $ in Millions	9 Months Ended
Dec. 31, 2020 USD ($)
Covid 19 pandemic
Unusual Or Infrequent Item Net Gain Loss [Abstract]
CARES act, estimated refund amount	$ 381.0

Estimated net operating loss carrybacks, depreciation adjustments reflected in Prepaid expense.

No definition available.

Name:	uhal_ReasonableEstimateRefundOperatingLossCarryback
Namespace Prefix:	uhal_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration