Summary of Available-for-Sale Debt Securities by Asset Type (Detail) - USD ($) $ in Thousands	May 31, 2023	May 31, 2022
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	$ 28,988	$ 26,669
Available-for-Sale Debt Securities, Gross Unrealized Gains	29	67
Available-for-Sale Debt Securities, Gross Unrealized Losses	(1,855)	(1,342)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	27,162	25,394
U.S. Treasury and other government
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	28,841	26,522
Available-for-Sale Debt Securities, Gross Unrealized Gains	23	55
Available-for-Sale Debt Securities, Gross Unrealized Losses	(1,843)	(1,338)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	27,021	25,239
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	147	147
Available-for-Sale Debt Securities, Gross Unrealized Gains	6	12
Available-for-Sale Debt Securities, Gross Unrealized Losses	(12)	(4)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	$ 141	$ 155

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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