Schedule of Available-for-sale Securities (Details) - USD ($) $ in Thousands		Apr. 30, 2021	Jul. 31, 2020
Marketable Securities [Line Items]
Amortized Cost		$ 16,973	$ 18,321
Gross Unrealized Gains		21	58
Gross Unrealized Losses		(142)	(16)
Fair Value		16,852	18,363
Certificates of Deposit [Member]
Marketable Securities [Line Items]
Amortized Cost	[1]	1,927	13,844
Gross Unrealized Gains	[1]		58
Gross Unrealized Losses	[1]
Fair Value	[1]	1,927	13,902
US Treasury Bill Securities [Member]
Marketable Securities [Line Items]
Amortized Cost		1,672	2,498
Gross Unrealized Gains
Gross Unrealized Losses		(28)
Fair Value		1,644	2,498
Corporate Bond Securities [Member]
Marketable Securities [Line Items]
Amortized Cost		6,283
Gross Unrealized Gains		21
Gross Unrealized Losses		(112)
Fair Value		6,192
Municipal Bonds [Member]
Marketable Securities [Line Items]
Amortized Cost		7,091	1,979
Gross Unrealized Gains
Gross Unrealized Losses		(2)	(16)
Fair Value		$ 7,089	$ 1,963

[1] Each of the Company’s certificates of deposit has a CUSIP, was purchased in the secondary market through a broker and may be sold in the secondary market.