Schedule V - AMERCO and Consolidated Subsidiaries, Supplemental Information (for Property-Casualty Insurance Operations) (Details) - Property Casualty Insurance Operations [Member] - Amerco [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental Information For Property And Casualty Insurance Underwriters [Abstract]
Deferred policy acquisition costs	$ 0	$ 0	$ 0
Reserves for unpaid claims and claims adjustment expense	177,963	209,127	228,970
Discount if any, deducted	(294)	233	239
Unearned premiums	70,283	69,138	60,853
Net earned premiums (1)	16,335	19,926	9,373
Net investment income (2)	20,670	22,137	19,579
Claim and claim adjustment expenses incurred related to current year	(3,865)	(9,535)	(5,365)
Amortization of deferred policy acquisition costs	0	0	0
Paid claims and claim adjustment expense	25,759	24,608	19,228
Net premiums written (1)	$ 69,989	$ 66,277	$ 61,022