Borrowings (Narratives) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Debt instruments, face, payment, and remaining balance amount:
Line of credit facility, outstanding balance	$ 585,924		$ 516,946	$ 542,186	$ 508,350
Notes, loans and leases payable	3,686,572			3,686,572		$ 3,513,076
Interest paid related to derivative contracts [Abstract]
Interest paid in cash	36,600		$ 32,400	71,100	$ 63,400
Real estate loan [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	107,913			107,913		135,287
Senior Mortgages [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	1,510,404			1,510,404		1,487,645
Working Capital Loans [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 185,000			$ 185,000		55,000
Working capital loans two [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.07%			2.07%
Applicable margin interest rate	1.38%			1.38%
Sum of LIBOR and margin	3.45%			3.45%
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	150,000			150,000
Line of credit facility, outstanding balance				$ 100,000
Debt instruments, issuance and maturity dates:
Debt instrument, maturity date				Sep. 30, 2020
Rental Truck (amortizing loans) First Loan [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	286,987			$ 286,987		342,971
Capital Lease Obligations [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	1,026,092			1,026,092		984,217
Capital Lease Obligations [Member] | AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
New capital lease obligiations, amount				187,100
Notes, loans and leases payable	1,026,100			1,026,100		984,200
Capitalized assets, net book value	1,499,400			$ 1,499,400		1,407,600
Debt instruments, miscellaneous information:
Terms of lease				Between 5 and 7 years
Other Obligations [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 75,200			$ 75,200		$ 73,579
Amerco Real Estate Subsidiaries and Uhaul Company of Florida [Member] | Real estate loan [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.13%			2.13%
Applicable margin interest rate	1.50%			1.50%
Sum of LIBOR and margin	3.63%			3.63%
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 107,900			$ 107,900
Debt instruments, issuance and maturity dates:
Mortgage loans on real estate, final maturity date				Apr. 30, 2023
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Senior Mortgages [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 1,510,400			$ 1,510,400
Debt instruments, issuance and maturity dates:
Debt instrument, maturity date range, start				Jan. 01, 2021
Debt instrument, maturity date range, end				Dec. 31, 2038
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%			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%			6.62%
Various Subsidiaries of Amerco Real Estate and Uhaul Intl [Member] | Working Capital Loans [Member] | AMERCO [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.08%			2.08%
Applicable margin interest rate	1.38%			1.38%
Sum of LIBOR and margin	3.46%			3.46%
Debt instruments, face, payment, and remaining balance amount:
Line of credit facility, maximum borrowing capacity	$ 85,000			$ 85,000
Line of credit facility, outstanding balance				$ 85,000
Debt instruments, issuance and maturity dates:
Debt instrument, maturity date				Jun. 30, 2021
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) First Loan [Member] | Uhaul International, Inc and AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 287,000			$ 287,000
Debt instruments, issuance and maturity dates:
Debt instrument, maturity date range, start				Dec. 01, 2018
Debt instrument, maturity date range, end				Jun. 30, 2025
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) First Loan [Member] | Uhaul International, Inc and AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	2.82%			2.82%
Debt instruments, interest rate, effective percentage:
LIBOR	2.11%			2.11%
Applicable margin interest rate	1.72%			1.72%
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) First Loan [Member] | Uhaul International, Inc and AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	3.00%			3.00%
Debt instruments, interest rate, effective percentage:
LIBOR	2.16%			2.16%
Applicable margin interest rate	1.75%			1.75%
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) second loan [Member] | Uhaul International, Inc and AMERCO [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 263,400			$ 263,400
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) second loan [Member] | Uhaul International, Inc and AMERCO [Member] | Minimum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	1.95%			1.95%
Uhaul Intl and Subsidiaries [Member] | Rental Truck (amortizing loans) second loan [Member] | Uhaul International, Inc and AMERCO [Member] | Maximum [Member]
Debt instruments, interest rate, stated percentage:
Debt instrument, interest rate, stated percentage	4.66%			4.66%
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:
Debt instrument, aggregate amount	$ 530,000			$ 530,000
Notes, loans and leases payable	$ 520,000			$ 520,000
Debt instruments, issuance and maturity dates:
Debt instrument, maturity date range, start				Jan. 01, 2021
Debt instrument, maturity date range, end				Jul. 31, 2022
Uhaul Intl and Subsidiaries [Member] | Rental Truck Revolvers [Member] | Minimum [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.08%			2.08%
Sum of LIBOR and margin	3.23%			3.23%
Uhaul Intl and Subsidiaries [Member] | Rental Truck Revolvers [Member] | Maximum [Member]
Debt instruments, interest rate, effective percentage:
LIBOR	2.11%			2.11%
Sum of LIBOR and margin	3.26%			3.26%
Amerco, Us Bank, National Association, Trustee [Member] | Other Obligations [Member]
Debt instruments, face, payment, and remaining balance amount:
Notes, loans and leases payable	$ 78,600			$ 78,600
Subsidiary holdings of parent company debt	$ 3,400			$ 3,400
Debt instruments, issuance and maturity dates:
Debt instrument, maturity date range, start				Dec. 31, 2018
Debt instrument, maturity date range, end				Dec. 31, 2047
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%
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%
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		123,400
Available for sale equity securities pledged as collateral		$ 70,000
Life Insurance [Member] | Federal Home Loan Bank [Member] | Minimum [Member]
Federal Home Loan Bank, Advances, Activity for the year [Abstract]
Deposit interest rate		1.48%
Deposit maturity date		Sep. 29, 2018
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%
Deposit maturity date		Mar. 29, 2021