Borrowings (Narratives) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021	Mar. 31, 2021
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 5,397,856		$ 5,397,856			$ 4,668,907
Interest paid related to derivative contracts [Abstract]
Interest paid in cash	35,400	$ 38,400	$ 106,900	$ 116,900
Real estate loan [Member]
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2023
Real estate loans (revolving credit) [Member]
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2025
Finance Lease [Member]
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2029
Finance Lease [Member] | AMERCO [Member]
Lease Cost [Abstract]
Sale Leaseback Transaction Lease Terms			(7) year terms
Finance Lease [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, face, payment, and remaining balance amount:
Capitalized assets, net book value	$ 692,800		$ 692,800
Finance Lease [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	5.04%		5.04%
Debt instruments, face, payment, and remaining balance amount:
Capitalized assets, net book value	$ 877,000		$ 877,000
Capital Lease Obligations [Member] | AMERCO [Member]
Lease Cost [Abstract]
Sale Leaseback Transaction Lease Terms			(7) years
Capital Lease Obligations [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.60%		1.60%
Capital Lease Obligations [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.22%		4.22%
Private Placement [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Amounts held at LIBOR plus margin	$ 100,000		$ 100,000		$ 150,000
New capital lease obligiations, amount	600,000		$ 600,000
Line of credit facility increase, amount	$ 150,000
Private Placement [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.55%		2.55%		2.43%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year	2030
Private Placement [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.88%		2.88%		2.78%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year	2035
Other Obligations [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.50%		1.50%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2022
Other Obligations [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	8.00%		8.00%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2049
Amerco Real Estate Subsidiaries and Uhaul Company of Florida [Member] | Real estate loan [Member]
Debt instruments, interest rate, effective percentage:
Applicable margin interest rate	1.50%		1.50%
Sum of LIBOR and margin, maximum rate	1.61%		1.61%
Amerco Real Estate Company [Member] | Rental Truck (amortizing loans) First Loan [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.61%		1.61%
Amerco Real Estate Company [Member] | Rental Truck (amortizing loans) First Loan [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.66%		4.66%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Senior Mortgages [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.70%		2.70%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Senior Mortgages [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	5.50%		5.50%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Working capital loans two [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Line of credit, current borrowing capacity	$ 385,000		$ 385,000
Notes, loans and leases payable	$ 385,000		$ 385,000
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Working capital loans two [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, effective percentage:
Applicable margin interest rate	1.25%		1.25%
Sum of LIBOR and margin, maximum rate	1.34%		1.34%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Working capital loans two [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, effective percentage:
Applicable margin interest rate	1.50%		1.50%
Sum of LIBOR and margin, maximum rate	1.59%		1.59%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Rental Truck Revolvers [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Line of credit facility, maximum borrowing capacity	$ 375,000		$ 375,000
Line of credit, current borrowing capacity	590,000		590,000
Notes, loans and leases payable	$ 550,000		$ 550,000
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Rental Truck Revolvers [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	0.09%		0.09%
Applicable margin interest rate	1.15%		1.15%
Sum of LIBOR and margin, maximum rate	1.25%		1.25%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Rental Truck Revolvers [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	0.10%		0.10%
Applicable margin interest rate	1.25%		1.25%
Sum of LIBOR and margin, maximum rate	1.34%		1.34%
Uhaul Intl and Subsidiaries [Member] | Real estate loans (revolving credit) [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
Applicable margin interest rate	1.38%		1.38%
Sum of LIBOR and margin, maximum rate	1.47%		1.47%
Unused capacity fee			0.30%
Debt instruments, face, payment, and remaining balance amount:
Line of credit facility, maximum borrowing capacity	$ 300,000		$ 300,000
Line of credit, current borrowing capacity	200,000		200,000
Line of credit facility, remaining borrowing capacity	$ 150,000		$ 150,000
Uhaul Intl and Subsidiaries [Member] | Real estate loans (revolving credit) [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	0.09%		0.09%
Amerco, Us Bank, National Association, Trustee [Member] | Other Obligations [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Debt instrument, face amount	$ 90,100		$ 90,100
Subsidiary holdings of parent company debt	$ 2,300		$ 2,300
Life Insurance [Member] | Other Obligations [Member] | Federal Home Loan Bank [Member]
Federal Home Loan Bank, Advances, Activity for the year [Abstract]
Aggregate deposit amount					$ 60,000
Available for sale equity securities, noncurrent					110,000
Available for sale equity securities pledged as collateral					$ 66,500
Life Insurance [Member] | Other Obligations [Member] | Federal Home Loan Bank [Member] | Minimum [Member]
Federal Home Loan Bank, Advances, Activity for the year [Abstract]
Deposit interest rate					0.49%
Life Insurance [Member] | Other Obligations [Member] | Federal Home Loan Bank [Member] | Maximum [Member]
Federal Home Loan Bank, Advances, Activity for the year [Abstract]
Deposit interest rate					1.72%