SCHEDULE II - Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts - USD ($)	12 Months Ended
	May 31, 2022	May 31, 2021	May 31, 2020
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 608,000	$ 1,521,000	$ 1,150,000
Charged to Costs and Expenses	959,000	(254,000)	580,000
Uncollectable Accounts Charged to Allowance	(275,000)	(659,000)	(209,000)
Balance at End of Period	$ 1,292,000	$ 608,000	$ 1,521,000