Allowance for Credit Losses (Narratives) (Details) $ in Millions	6 Months Ended
Sep. 30, 2020 USD ($)
Receivables [Abstract]
Trade receivable components	2
Historical loss rate	5.00%
Allowance for expected credit losses	$ 2.3
Available for sale securites, accrued interest receivable	$ 25.8
Financing Receivable Additional Disclosures [Abstract]
Reinsurance paid percentage of total assets	1.00%
Premiums Receivable Gross	$ 3.0
Credit card receivables
Receivables [Abstract]
Average Historical Chargeback Term	For credit card receivable, the Company uses a trailing 13 months average historical chargeback percentage of total credit card receivable.
Accrued interest receivables
Receivables [Abstract]
Rental Equipment Payment Term	The Company rents equipment to corporate customers in which payment terms are 30 days.
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable Additional Disclosures [Abstract]
Modeling of mortgage loans	The portfolio of mortgage loans are principally collateralized by self-storage facilities and commercial properties. Mortgage loans that management has the intent and ability to hold for the foreseeable future, or until maturity or payoff, are reported at amortized cost. Modeling for our mortgage loans is based on inputs most highly correlated to defaults, including loan-to-value, occupancy, and payment history. Historical credit loss experience provides additional support for the estimation of expected credit losses. In assessing the credit losses, the portfolio is reviewed on a collective basis, using loan-specific cash flows to determine the fair value of the collateral in the event of default. Adjustments to this analysis are made to assess loans with a loan-to-value of 65% or greater. Loans that fall under the >65% LTV are evaluated on an individual basis and loan specific risk characteristics such as occupancy levels, expense, income growth and other relevant available information from internal and external sources relating to post events, current conditions, and reasonable and supportable forecasts

Evaluation and assessment of customer credit worthiness over a specified time.

No definition available.

Name:	uhal_AverageHistoricalChargebackTerm
Namespace Prefix:	uhal_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Term period for rental equipment with corporate customers.

+ References

No definition available.

+ Details

Name:	uhal_RentalEquipmentPaymentTerm
Namespace Prefix:	uhal_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13531-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13537-108611

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Ratio of insurance contracts that are subject to reinsurance participation to all contracts in force.

+ References

No definition available.

+ Details

Name:	us-gaap_ContractsInForceSubjectToParticipationThroughReinsurancePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableAdditionalDisclosuresAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Includes any additional disclosures related to the credit quality of financing receivables. This may include a description of a credit quality indicator or a description of how the internal risk ratings used by a company relate to the likelihood of loss.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 29
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953659-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 30
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953664-111524

+ Details

Name:	us-gaap_FinancingReceivableCreditQualityAdditionalInformation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The gain (loss) resulting from the sale of credit card receivables (portfolios).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107207-111719

+ Details

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

- Definition

Carrying amount as of the balance sheet date of noncurrent interest earned but not received. Also called accrued interest or accrued interest receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_InterestReceivableNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

+ Details

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Gross amount, as of the balance sheet date, due the entity from (a) agents and insureds, (b) uncollected premiums and (c) others, before deducting the allowance for doubtful accounts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.5)
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

Name:	us-gaap_PremiumsReceivableGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_ReceivablesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CreditCardReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_UnfundedLoanCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: