Debt Securities (Tables)

3 Months Ended

Oct. 31, 2020

Investments, Debt and Equity Securities [Abstract]

Schedule of available-for-sale securities

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
	(in thousands)
October 31, 2020:
Certificates of deposit*	$	7,537	$	30	$	—		$	7,567
U.S. Treasury bills and notes		4,179		—		(8	)		4,171
Corporate bonds		6,238		14		(21	)		6,231
Municipal bonds		5,923		—		(2	)		5,921
Total	$	23,877	$	44	$	(31	)	$	23,890
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	$	12,644
After one year through five years		4,017
After five years through ten years		5,983
After ten years		1,246
Total	$	23,890

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

	Unrealized Losses		Fair Value
	(in thousands)
October 31, 2020:
U.S. Treasury bills and notes	$	8	$	1,673
Corporate bonds		21		3,593
Municipal bonds		2		4,623
Total	$	31	$	9,889
July 31, 2020:
Municipal bonds	$	16	$	1,963