Borrowings (Narratives) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Mar. 31, 2019
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 4,548,609		$ 4,548,609			$ 4,163,323
Debt instruments, issuance and maturity dates:
Remaining Lease Term Finance Lease Weighted Average			4 Years
Interest paid related to derivative contracts [Abstract]
Interest paid in cash	$ 41,900	$ 38,500	$ 127,800	$ 109,600
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			2024
Working capital loans two [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	1.70%		1.70%
Applicable margin interest rate	1.38%		1.38%
Sum of LIBOR and margin, maximum rate	3.08%		3.08%
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	$ 150,000		$ 150,000
Rental Truck (amortizing loans) First Loan [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.95%		1.95%
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%
Finance Lease [Member]
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2026
Amerco Real Estate Subsidiaries and Uhaul Company of Florida [Member] | Real estate loan [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	1.72%		1.72%
Applicable margin interest rate	1.50%		1.50%
Sum of LIBOR and margin, maximum rate	3.22%		3.22%
Amerco Real Estate Company [Member] | Real estate loans (revolving credit) [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	1.70%		1.70%
Debt instruments, face, payment, and remaining balance amount:
Line of credit facility, maximum borrowing capacity	$ 335,000		$ 335,000
Amerco Real Estate Company [Member] | Real estate loans (revolving credit) [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	2.95%		2.95%
Amerco Real Estate Company [Member] | Real estate loans (revolving credit) [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	3.20%		3.20%
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	3.36%		3.36%
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%
Uhaul Intl and Subsidiaries [Member] | Rental Truck Revolvers [Member]
Debt instruments, interest rate, effective percentage:
Applicable margin interest rate	1.15%		1.15%
Debt instruments, face, payment, and remaining balance amount:
Line of credit, current borrowing capacity	$ 590,000		$ 590,000
Uhaul Intl and Subsidiaries [Member] | Capital Lease Obligations [Member]
Debt instruments, issuance and maturity dates:
Remaining Lease Term Finance Lease Weighted Average			7 year terms
Uhaul Intl and Subsidiaries [Member] | Capital Lease Obligations [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.92%		1.92%
Uhaul Intl and Subsidiaries [Member] | Capital Lease Obligations [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	5.04%		5.04%
Uhaul Intl and Subsidiaries [Member] | Finance Lease [Member]
Debt instruments, issuance and maturity dates:
Remaining Lease Term Finance Lease Weighted Average			7 years
Uhaul Intl and Subsidiaries [Member] | Finance Lease [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.73%		2.73%
Uhaul Intl and Subsidiaries [Member] | Finance Lease [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.22%		4.22%
Amerco, Us Bank, National Association, Trustee [Member] | Other Obligations [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 87,000		$ 87,000
Subsidiary holdings of parent company debt	$ 2,900		$ 2,900
Amerco, Us Bank, National Association, Trustee [Member] | Other Obligations [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			2020
Amerco, Us Bank, National Association, Trustee [Member] | Other Obligations [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			2048
Life Insurance [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					120,100
Available for sale equity securities pledged as collateral					$ 67,900
Life Insurance [Member] | Federal Home Loan Bank [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage					1.72%
Life Insurance [Member] | Federal Home Loan Bank [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage					2.95%