Schedule I - Condensed Financial Information of AMERCO (Statements of Operations) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Net interest income from subs	$ 3,601,114	$ 3,421,767	$ 3,275,468
Expenses:
Operating expenses	1,807,983	1,568,083	1,470,047
Total costs and expenses	2,836,795	2,679,504	2,408,842
Equity in earnings of subsidiaries
Pretax earnings	637,613	628,358	768,911
Income tax expense	152,970	(229,934)	(279,910)
Earnings available to common shareholders	$ 790,583	$ 398,424	$ 489,001
Basic and diluted earnings per common share	$ 40.36	$ 20.34	$ 24.95
Weighted average common shares outstanding: basic and diluted	19,588,889	19,586,606	19,596,110
Amerco [Member]
Revenues:
Net interest income from subs	$ 4,606	$ 1,912	$ 2,420
Expenses:
Operating expenses	7,003	7,115	7,525
Other expenses	91	109	111
Total costs and expenses	7,094	7,224	7,636
Equity in earnings of subsidiaries	681,786	327,773	417,087
Interest income	120,549	103,211	93,873
Pretax earnings	799,847	425,672	505,744
Income tax expense	(9,264)	(27,248)	(16,743)
Earnings available to common shareholders	$ 790,583	$ 398,424	$ 489,001
Weighted average common shares outstanding: basic and diluted	19,588,889	19,586,606	19,596,110