Schedule I - Condensed Financial Information of AMERCO (Statements of Operations) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Revenues:
Net interest income from subs	$ 4,541,985	$ 3,978,868	$ 3,768,707
Expenses:
Operating expenses	2,187,684	2,117,148	1,981,180
Total costs and expenses	3,580,838	3,438,740	3,147,720
Equity in earnings of subsidiaries	0	0	0
Pretax earnings	796,658	378,124	477,529
Income tax expense	(185,802)	63,924	(106,672)
Earnings available to common shareholders	$ 610,856	$ 442,048	$ 370,857
Basic and diluted earnings per common share	$ 31.15	$ 22.55	$ 18.93
Weighted average common shares outstanding: basic and diluted	19,607,788	19,603,708	19,592,048
Amerco [Member]
Revenues:
Net interest income from subs	$ 720	$ 6,586	$ 8,601
Expenses:
Operating expenses	6,753	10,622	8,840
Other expenses	115	96	93
Total costs and expenses	6,868	10,718	8,933
Equity in earnings of subsidiaries	508,632	205,940	279,589
Interest income	135,673	130,670	112,649
Pretax earnings	638,157	332,478	391,906
Income tax expense	(27,301)	109,570	(21,049)
Earnings available to common shareholders	$ 610,856	$ 442,048	$ 370,857
Basic and diluted earnings per common share	$ 31.15	$ 22.55	$ 18.93
Weighted average common shares outstanding: basic and diluted	19,607,788	19,603,708	19,592,048