Borrowings (Long-term Debt Borrowings) (Details) - USD ($) $ in Thousands	9 Months Ended
Dec. 31, 2017	Mar. 31, 2017
Debt instrument, maturities:
Notes, loans and leases payable, gross	$ 3,519,978	$ 3,287,233
Less: Debt issuance costs	(26,070)	(24,353)
Total notes, loans and leases payable	$ 3,493,908	3,262,880
Real estate loan (amortizing term) [Member]
Debt instrument, maturities:
Debt instrument, maturity year	2023
Total notes, loans and leases payable	$ 137,786	169,289
Real estate loan (amortizing term) [Member] \| Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.94%
Real estate loan (amortizing term) [Member] \| Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	6.93%
Senior Mortgages [Member]
Debt instrument, maturities:
Debt instrument, maturity year range, start	2021
Debt instrument, maturity year range, end	2038
Total notes, loans and leases payable	$ 1,472,209	1,292,160
Senior Mortgages [Member] \| Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	3.72%
Senior Mortgages [Member] \| Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	6.62%
Working capital loan (revolving credit) [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.83%
Debt instrument, maturities:
Debt instrument, maturity year	2018
Total notes, loans and leases payable	$ 55,000	85,000
Fleet loans (amortization term) [Member]
Debt instrument, maturities:
Debt instrument, maturity year range, start	2018
Debt instrument, maturity year range, end	2024
Total notes, loans and leases payable	$ 322,542	324,977
Fleet loans (amortization term) [Member] \| Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.95%
Fleet loans (amortization term) [Member] \| Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.76%
Fleet loans (securitization) [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.90%
Debt instrument, maturities:
Total notes, loans and leases payable		52,112
Fleet loans (revolving credit) [Member]
Debt instrument, maturities:
Debt instrument, maturity year range, start	2020
Debt instrument, maturity year range, end	2021
Total notes, loans and leases payable	$ 477,000	417,000
Fleet loans (revolving credit) [Member] \| Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.50%
Fleet loans (revolving credit) [Member] \| Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.51%
Capital Leases (rental equipment) [Member]
Debt instrument, maturities:
Debt instrument, maturity year range, start	2018
Debt instrument, maturity year range, end	2025
Total notes, loans and leases payable	$ 982,653	876,828
Capital Leases (rental equipment) [Member] \| Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.92%
Capital Leases (rental equipment) [Member] \| Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.86%
Other Obligations [Member]
Debt instrument, maturities:
Debt instrument, maturity year range, start	2018
Debt instrument, maturity year range, end	2047
Total notes, loans and leases payable	$ 72,788	$ 69,867
Other Obligations [Member] \| Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.75%
Other Obligations [Member] \| Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	8.00%

The latest maturity year for these debt instruments.

No definition available.

Name:	uhal_MaturityEndYear
Namespace Prefix:	uhal_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

The earliest maturity year for these debt instruments.

+ References

No definition available.

+ Details

Name:	uhal_MaturityStartYear
Namespace Prefix:	uhal_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

The DebtInstrumentMaturityDate could have worked for this element, but it must include the format Month-Date-Year. Will use this US-GAAP Element in the next few schedules, when possible, where we break down the various items that make up the Borrowing's narrative.

+ References

No definition available.

+ Details

Name:	uhal_MaturityYear
Namespace Prefix:	uhal_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_DebtAndCapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-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=6877327&loc=d3e13212-122682

+ Details

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

- References

No definition available.

+ Details

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

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

+ Details

Name:	us-gaap_LongTermDebtPercentageBearingFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_MortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_MediumTermNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=uhal_FleetLoanSecuritizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=uhal_FleetLoansRevolvingCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_CapitalLeaseObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: