Accounting Pronouncements (Narratives) (Details) $ in Thousands	6 Months Ended
Sep. 30, 2020 USD ($)
Allowance For Credit Loss [Abstract]
Allowance For Doubtful Accounts Provision For Credit Losses	$ 2,880

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