Summary of Available-for-Sale Debt Securities by Asset Type (Detail) - USD ($) $ in Thousands	May 31, 2022	May 31, 2021
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	$ 26,669	$ 26,297
Available-for-Sale Debt Securities, Gross Unrealized Gains	67	632
Available-for-Sale Debt Securities, Gross Unrealized Losses	(1,342)	(184)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	25,394	26,745
U.S. Treasury and other government
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	26,522	26,154
Available-for-Sale Debt Securities, Gross Unrealized Gains	55	593
Available-for-Sale Debt Securities, Gross Unrealized Losses	(1,338)	(184)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	25,239	26,563
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	147	143
Available-for-Sale Debt Securities, Gross Unrealized Gains	12	39
Available-for-Sale Debt Securities, Gross Unrealized Losses	(4)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	$ 155	$ 182

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
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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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