Schedule of Available-for-sale Securities, Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jul. 31, 2021	Jul. 31, 2020
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 50
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4,945
US Treasury Bill Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	17
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,652
Corporate Bond Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	33
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 3,293
Municipal Bonds [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 16
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 1,963