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, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Information For Property And Casualty Insurance Underwriters [Abstract]
Deferred policy acquisition costs	$ 0	$ 0	$ 0
Reserves for unpaid claims and claims adjustment expense	209,127	228,970	233,554
Unearned premiums	69,138	60,853	57,100
Net earned premiums (1)	19,926	9,373	14,079
Net investment income (2)	22,137	19,579	15,749
Claim and claim adjustment expenses incurred related to current year	(9,535)	(5,365)	233
Amortization of deferred policy acquisition costs	0	0	0
Paid claims and claim adjustment expense	24,608	19,228	17,366
Net premiums written (1)	$ 66,277	$ 61,022	$ 57,123