Borrowings (Narratives) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Mar. 31, 2019
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 4,497,912		$ 4,497,912			$ 4,163,323
Debt instruments, issuance and maturity dates:
Remaining Lease Term Finance Lease Weighted Average	5 Years
Interest paid related to derivative contracts [Abstract]
Interest paid in cash	$ 45,400	$ 36,600	$ 85,900	$ 71,100
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	2.11%		2.11%
Applicable margin interest rate	1.38%		1.38%
Debt instrument, interest rate at period end			3.49%
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
Line of credit facility, remaining borrowing capacity	$ 100,000		$ 100,000
Rental Truck (amortizing loans) First Loan [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.03%		2.03%
Applicable margin interest rate	1.75%		1.75%
Debt instrument, interest rate at period end			3.78%
Sum of LIBOR and margin, maximum rate	2.82%		2.82%
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	2.05%		2.05%
Applicable margin interest rate	1.50%		1.50%
Debt instrument, interest rate at period end			3.55%
Amerco Real Estate Company [Member] | Real estate loans (revolving credit) [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.11%		2.11%
Debt instruments, face, payment, and remaining balance amount:
Line of credit, current borrowing capacity	$ 335,000		$ 335,000
Notes, loans and leases payable	$ 335,000		$ 335,000
Amerco Real Estate Company [Member] | Real estate loans (revolving credit) [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%
Debt instrument, interest rate at period end			3.36%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2022
Amerco Real Estate Company [Member] | Real estate loans (revolving credit) [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%
Debt instrument, interest rate at period end			3.61%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2024
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:
Notes, loans and leases payable	$ 580,000		$ 580,000
Uhaul Intl and Subsidiaries [Member] | Rental Truck Revolvers [Member] | Minimum [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.10%		2.10%
Debt instrument, interest rate at period end			3.25%
Uhaul Intl and Subsidiaries [Member] | Rental Truck Revolvers [Member] | Maximum [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.12%		2.12%
Debt instrument, interest rate at period end			3.27%
Uhaul Intl and Subsidiaries [Member] | Capital Lease Obligations [Member]
Debt instruments, face, payment, and remaining balance amount:
New capital lease obligiations, amount			$ 861,800
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, face, payment, and remaining balance amount:
Sale leaseback transactions loss amount			$ 339,400
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	2.97%		2.97%
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	$ 86,500		$ 86,500
Subsidiary holdings of parent company debt	$ 3,000		$ 3,000
Amerco, Us Bank, National Association, Trustee [Member] | Other Obligations [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.75%		2.75%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year			2019
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					131,100
Available for sale equity securities pledged as collateral					$ 68,800
Life Insurance [Member] | Federal Home Loan Bank [Member] | Minimum [Member]
Federal Home Loan Bank, Advances, Activity for the year [Abstract]
Deposit interest rate					1.67%
Life Insurance [Member] | Federal Home Loan Bank [Member] | Maximum [Member]
Federal Home Loan Bank, Advances, Activity for the year [Abstract]
Deposit interest rate					2.95%