Schedule I - Condensed Financial Information of AMERCO (Statements of Cash Flow) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Cash flow from operating activities:
Net earnings	$ 610,856	$ 442,048	$ 370,857
Earnings from consolidated subsidiaries	0	0	0
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	664,001	664,120	581,025
Net loss on sales of investments	(10,058)	(13,596)	(2,663)
Deferred income taxes	68,411	317,893	106,811
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(39,516)	38,129	(31,365)
Prepaid expenses	94,359	(391,120)	(8,620)
Other assets	29,865	(1,295)	157,152
Related party assets	(487)	(5,645)	4,194
Accounts payable and accrued expenses	92,925	(4,530)	10,263
Net cash provided by operating activities	1,535,395	1,075,513	975,583
Cash flow from investing activities:
Purchases of property, plant and equipment	(1,441,475)	(2,309,406)	(1,869,968)
Proceeds of equity securities	207	185	8,608
Net cash used by investing activities	(1,129,529)	(1,766,649)	(1,571,136)
Cash flow from financing activities:
Borrowings from credit facilities	922,008	1,121,412	897,311
Principal repayments on credit facilities	(662,588)	(349,986)	(299,748)
Debt issuance costs	(5,793)	(5,332)	(7,243)
Common stock dividends paid	(49,019)	(29,404)	(39,179)
Net contribution from (to) related party	0	0
Net Cash Provided by (Used in) Financing Activities	287,353	512,320	514,582
Effects of exchange rate on cash	6,441	(533)	(4,716)
Increase (decrease) in cash and cash equivalents	699,660	(179,349)	(85,687)
Cash and cash equivalents at the beginning of period	494,352	673,701	759,388
Cash and cash equivalents at the end of the period	1,194,012	494,352	673,701
Amerco [Member]
Cash flow from operating activities:
Net earnings	610,856	442,048	370,857
Earnings from consolidated subsidiaries	(508,632)	(205,940)	(279,589)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	1	1	1
Net loss on sales of investments	924	0	0
Deferred income taxes	72,407	323,980	112,434
Net change in other operating assets and liabilities:
Prepaid expenses	88,898	(381,190)	(6,289)
Other assets	0	22	(40)
Related party assets	(12,000)	0	0
Accounts payable and accrued expenses	(4,019)	1,935	2,260
Net cash provided by operating activities	248,435	180,856	199,634
Cash flow from investing activities:
Purchases of property, plant and equipment	(3)	0	(1)
Proceeds of equity securities	0	0	0
Net cash used by investing activities	(3)	0	(1)
Cash flow from financing activities:
Borrowings from credit facilities	200,000	0	0
Principal repayments on credit facilities	(200,000)	0	0
Debt issuance costs	(924)	0	0
Proceeds from (repayments) of intercompany loans	211,064	(311,534)	(196,382)
Common stock dividends paid	(49,019)	(29,404)	(39,179)
Net contribution from (to) related party	41,199	21,600	0
Net Cash Provided by (Used in) Financing Activities	202,320	(319,338)	(235,561)
Effects of exchange rate on cash	5,773	4,060	(4,331)
Increase (decrease) in cash and cash equivalents	456,525	(134,422)	(40,259)
Cash and cash equivalents at the beginning of period	294,528	428,950	469,209
Cash and cash equivalents at the end of the period	$ 751,053	$ 294,528	$ 428,950