Related Party Transactions (Related Party Assets) (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Mar. 31, 2017
Related party assets:
Related party assets		$ 80,865	$ 86,168
Sac Holdings [Member]
Related party assets:
Notes receivable		47,783	48,098
U-Haul interest receivable		5,498	5,397
U-Haul receivables		20,050	23,202
Mercury [Member]
Related party assets:
U-Haul receivables		4,804	9,195
Insurance Group [Member]
Related party assets:
Other	[1]	$ 2,730	$ 276

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