Related Party Transactions (Related Party Assets) (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Mar. 31, 2018
Related party assets:
U-Haul receivables		$ 5,523	$ 4,284
Related party assets		30,889	33,276
Blackwater [Member]
Related party assets:
U-Haul receivables		25,158	24,034
Mercury [Member]
Related party assets:
U-Haul receivables		7,234	10,357
Insurance Subsidiaries [Member]
Related party assets:
Other	[1]	$ (1,503)	$ (1,115)

[1] Timing differences for intercompany balances with insurance subsidiaries resulting from the three month difference in reporting periods