Debt Securities (Tables)

6 Months Ended

Jan. 31, 2021

Investments, Debt and Equity Securities [Abstract]

Schedule of available-for-sale securities

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(in thousands)
January 31, 2021:
Certificates of deposit*	$	4,608	$	15	$	—		$	4,623
U.S. Treasury bills and notes		3,676		—		(9	)		3,667
Corporate bonds		6,233		68		(17	)		6,284
Municipal bonds		6,925		2		—			6,927
Total	$	21,442	$	85	$	(26	)	$	21,501
July 31, 2020:
Certificates of deposit*	$	13,844	$	58	$	—		$	13,902
U.S. Treasury bills		2,498		—		—			2,498
Municipal bonds		1,979		—		(16	)		1,963
Total	$	18,321	$	58	$	(16	)	$	18,363

Schedule of contractual maturities of available-for-sale debt securities

	Fair Value
	(in thousands)
Within one year	$	9,688
After one year through five years		6,447
After five years through ten years		4,611
After ten years		755
Total	$	21,501

Schedule of available-for-sale securities, unrealized loss position

	Unrealized Losses		Fair Value
	(in thousands)
January 31, 2021:
U.S. Treasury bills and notes	$	9	$	1,667
Corporate bonds		17		1,690
Total	$	26	$	3,357
July 31, 2020:
Municipal bonds	$	16	$	1,963