Related Party Transactions (Related Party Assets) (Details) - USD ($) $ in Thousands		Dec. 31, 2016	Mar. 31, 2016
Related party assets:
Related party assets		$ 91,705	$ 85,734
Sac Holdings [Member]
Related party assets:
Notes receivable		48,429	49,322
U-Haul interest receivable		5,288	4,970
U-Haul receivables		27,466	23,127
Mercury [Member]
Related party assets:
U-Haul receivables		9,930	8,016
Insurance Group [Member]
Related party assets:
Other	[1]	$ 592	$ 299

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