Related Party Transactions (Related Party Assets) (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Mar. 31, 2018
Related party assets:
Related party assets		$ 30,257	$ 33,276
Blackwater [Member]
Related party assets:
U-Haul receivables		24,172	24,034
Mercury [Member]
Related party assets:
U-Haul receivables		5,044	10,357
Insurance Group [Member]
Related party assets:
Other	[1]	$ 1,041	$ (1,115)

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