Borrowings (Narratives) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2020
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 4,678,227		$ 4,678,227		$ 4,621,291
Debt instruments, issuance and maturity dates:
Remaining Lease Term Finance Lease Weighted Average			4
Interest paid related to derivative contracts [Abstract]
Interest paid in cash	$ 38,400	$ 41,900	$ 116,900	$ 127,800
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
Capital Lease Obligations [Member] | AMERCO [Member]
Lease Cost [Abstract]
Sale Leaseback Transaction Lease Terms			(7) year terms
Capital Lease Obligations [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.92%		1.92%
Capital Lease Obligations [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	5.04%		5.04%
Finance Lease [Member]
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2028
Finance Lease [Member] | AMERCO [Member]
Lease Cost [Abstract]
Sale Leaseback Transaction Lease Terms			(7) years
Finance Lease [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.60%		1.60%
Finance Lease [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.22%		4.22%
Other Obligations [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Line of credit, current borrowing capacity	$ 200,000		$ 200,000
Amerco Real Estate Subsidiaries and Uhaul Company of Florida [Member] | Real estate loan [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	0.15%		0.15%
Applicable margin interest rate	1.50%		1.50%
Sum of LIBOR and margin, maximum rate	1.65%		1.65%
Amerco Real Estate Company [Member] | Real estate loans (revolving credit) [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	1.00%		1.00%
Applicable margin interest rate	2.25%		2.25%
Sum of LIBOR and margin, maximum rate	3.25%		3.25%
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
Notes, loans and leases payable	$ 150,000		$ 150,000
Amerco Real Estate Company [Member] | Working capital loans two [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	0.15%		0.15%
Debt instruments, face, payment, and remaining balance amount:
Line of credit facility, maximum borrowing capacity	$ 385,000		$ 385,000
Notes, loans and leases payable	$ 385,000		$ 385,000
Amerco Real Estate Company [Member] | Working capital loans two [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	3.03%		3.03%
Debt instruments, interest rate, effective percentage:
Applicable margin interest rate	1.25%		1.25%
Sum of LIBOR and margin, maximum rate	1.40%		1.40%
Amerco Real Estate Company [Member] | Working capital loans two [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	3.14%		3.14%
Debt instruments, interest rate, effective percentage:
Applicable margin interest rate	1.50%		1.50%
Sum of LIBOR and margin, maximum rate	1.65%		1.65%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Senior Mortgages [Member]
Debt instruments, interest rate, effective percentage:
Debt Weighted Average Interest Rate	4.28%		4.28%
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	2.80%		2.80%
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	6.62%		6.62%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Rental Truck Revolvers [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	0.15%		0.15%
Applicable margin interest rate	1.15%		1.15%
Sum of LIBOR and margin, maximum rate	1.30%		1.30%
Debt instruments, face, payment, and remaining balance amount:
Line of credit, current borrowing capacity	$ 590,000		$ 590,000
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) First Loan [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.04%		2.04%
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) First Loan [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.66%		4.66%
Amerco, Us Bank, National Association, Trustee [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 87,400		$ 87,400
Subsidiary holdings of parent company debt	$ 2,500		$ 2,500
Amerco, Us Bank, National Association, Trustee [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.50%		2.50%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2021
Amerco, Us Bank, National Association, Trustee [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
Life Insurance [Member] | Federal Home Loan Bank [Member]
Federal Home Loan Bank, Advances, Activity for the year [Abstract]
Aggregate deposit amount	$ 76,500		$ 76,500
Available for sale equity securities, noncurrent	174,400		174,400
Available for sale equity securities pledged as collateral	$ 85,100		$ 85,100
Life Insurance [Member] | Federal Home Loan Bank [Member] | Minimum [Member]
Federal Home Loan Bank, Advances, Activity for the year [Abstract]
Deposit interest rate	0.00%		0.00%
Life Insurance [Member] | Federal Home Loan Bank [Member] | Maximum [Member]
Federal Home Loan Bank, Advances, Activity for the year [Abstract]
Deposit interest rate	2.67%		2.67%