Schedule I - Condensed Financial Information of AMERCO (Statements of Cash Flow) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Cash flow from operating activities:
Net earnings	$ 790,583	$ 398,424	$ 489,001
Earnings from consolidated subsidiaries
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	555,069	481,520	389,393
Net gains on sales of investments	(6,269)	(5,284)	(4,491)
Deferred income taxes	(193,434)	173,112	138,075
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(15,329)	(2,890)	14,765
Prepaid expenses	(40,765)	9,386	(10,338)
Other assets	(165,968)	(2,488)	16,261
Related party assets	53,408	343	56,644
Accounts payable and accrued expenses	(25,546)	(5,056)	37,312
Net cash provided by operating activities	936,328	1,058,119	1,045,346
Cash flow from investing activities:
Purchases of property, plant and equipment	(1,363,745)	(1,419,505)	(1,509,154)
Proceeds of equity securities			2,044
Net cash used by investing activities	(896,948)	(1,182,572)	(1,259,682)
Cash flow from financing activities:
Common stock dividends paid	(29,380)	(58,757)	(78,374)
Net Cash Provided by (Used in) Financing Activities	16,604	223,753	388,872
Effects of exchange rate on cash	5,598	(2,140)	(15,740)
Increase (decrease) in cash and cash equivalents	61,582	97,160	158,796
Cash and cash equivalents at the beginning of period	697,806	600,646	441,850
Cash and cash equivalents at the end of the period	759,388	697,806	600,646
Amerco [Member]
Cash flow from operating activities:
Net earnings	790,583	398,424	489,001
Earnings from consolidated subsidiaries	(681,786)	(327,773)	(417,087)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	3	10	6
Net gains on sales of investments		13
Deferred income taxes	(182,358)	173,059	124,838
Net change in other operating assets and liabilities:
Prepaid expenses	(36,516)	16,021	(8,723)
Other assets	65	(20)	6
Related party assets		1	56,849
Accounts payable and accrued expenses	278	(297)	(14)
Net cash provided by operating activities	(109,731)	259,438	244,876
Cash flow from investing activities:
Purchases of property, plant and equipment	(1)	(55)	(8)
Proceeds of equity securities		39
Net cash used by investing activities	(1)	(16)	(8)
Cash flow from financing activities:
Proceeds from (repayments) of intercompany loans	250,214	(221,124)	(76,354)
Common stock dividends paid	(29,380)	(58,757)	(78,374)
Net Cash Provided by (Used in) Financing Activities	220,834	(279,881)	(154,728)
Effects of exchange rate on cash	(3,124)
Increase (decrease) in cash and cash equivalents	107,978	(20,459)	90,140
Cash and cash equivalents at the beginning of period	361,231	381,690	291,550
Cash and cash equivalents at the end of the period	$ 469,209	$ 361,231	$ 381,690