Borrowings (Narratives) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 4,343,935		$ 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	$ 40,500	$ 34,400
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	2.44%
Applicable margin interest rate	1.38%
Sum of LIBOR and margin, maximum rate	3.82%
Debt instruments, face, payment, and remaining balance amount:
Line of credit facility, maximum borrowing capacity	$ 300,000
Line of credit, current borrowing capacity	150,000
Notes, loans and leases payable	100,000
Capital Lease Obligations [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 948,200
Debt instruments, issuance and maturity dates:
Remaining Lease Term Finance Lease Weighted Average	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%
Capital Lease Obligations [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	5.04%
Finance Lease [Member]
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year	2026
Finance Lease [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Sale leaseback transactions, amount	$ 259,600
Debt instruments, issuance and maturity dates:
Remaining Lease Term Finance Lease Weighted Average	7 years
Finance Lease [Member] | AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	3.21%
Finance Lease [Member] | AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.22%
Amerco Real Estate Subsidiaries and Uhaul Company of Florida [Member] | Real estate loan [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.41%
Applicable margin interest rate	1.50%
Sum of LIBOR and margin, maximum rate	3.91%
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	3.72%
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%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Real estate loans (revolving credit) [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Line of credit facility, maximum borrowing capacity	$ 335,000
Notes, loans and leases payable	$ 335,000
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [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%
Debt instruments, interest rate, effective percentage:
LIBOR	2.43%
Applicable margin interest rate	1.25%
Sum of LIBOR and margin, maximum rate	3.68%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year	2022
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [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%
Debt instruments, interest rate, effective percentage:
LIBOR	2.44%
Applicable margin interest rate	1.50%
Sum of LIBOR and margin, maximum rate	3.93%
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year	2024
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) First Loan [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.39%
Applicable margin interest rate	1.75%
Sum of LIBOR and margin, maximum rate	4.14%
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	1.95%
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%
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) second loan [Member] | AMERCO [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.82%
Uhaul Intl and Subsidiaries [Member] | Rental Truck Revolvers [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.44%
Applicable margin interest rate	1.15%
Sum of LIBOR and margin, maximum rate	3.59%
Debt instruments, face, payment, and remaining balance amount:
Line of credit, current borrowing capacity	$ 580,000
Line of credit facility increase, amount	$ 10,000
Uhaul Intl and Subsidiaries [Member] | Rental Truck Revolvers [Member] | Minimum [Member]
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year	2021
Uhaul Intl and Subsidiaries [Member] | Rental Truck Revolvers [Member] | Maximum [Member]
Debt instruments, issuance and maturity dates:
Debt instrument, maturity year	2024
Amerco, Us Bank, National Association, Trustee [Member] | Other Obligations [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 85,800
Subsidiary holdings of parent company debt	$ 3,100
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%
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%
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				127,900
Available for sale equity securities pledged as collateral				$ 69,800
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%