Accounting Pronouncements (Narratives) (Details) $ in Millions	9 Months Ended
Dec. 31, 2020 USD ($)
Cumulative Effect Period Of Adoption Adjustment [Member] \| Debt securities, estimated credit loss
Allowance For Credit Loss [Abstract]
Allowance For Doubtful Accounts Provision For Credit Losses	$ 2.9

Allowance for doubtful accounts, provision for credit losses in retained earnings.

No definition available.

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