Provision for Taxes (Narratives) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2018	Mar. 31, 2019
Components of Deferred Tax Assets and Liabilities [Abstract]
NOL and credit carryforwards, federal amount	$ 146,000
Federal statutory rate, blended rate for fiscal year	31.55%
Provisional benefit amount	$ 356,600
Deferred tax assets, effect of Tax Cuts and Jobs Act, tax expense (benefit)	371,500
Reclassified amount from accumulated other comprehensive income to retained earnings	8,700	$ 0
Provisional tax expense for foreign tax credits	10,700
Phase three tax, increase in income tax expense	4,200
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Unrecognized tax benefits, income tax penalties and interest accrued	12,800		$ 9,500
Unrecognized tax benefits, income tax penalties and interest expense	3,300
Amerco [Member]
Components of Deferred Tax Assets and Liabilities [Abstract]
NOL and credit carryfowards, state amount	$ 337,300		$ 172,300