Summary of Available-for-Sale Debt Securities by Asset Type (Detail) - USD ($) $ in Thousands	May 31, 2020	May 31, 2019
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	$ 25,605	$ 24,905
Available-for-Sale Debt Securities, Gross Unrealized Gains	1,357	415
Available-for-Sale Debt Securities, Gross Unrealized Losses	(40)	(311)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	26,922	25,009
U.S. Treasury and other government
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	25,462	24,483
Available-for-Sale Debt Securities, Gross Unrealized Gains	1,314	372
Available-for-Sale Debt Securities, Gross Unrealized Losses	(40)	(308)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	26,736	24,547
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	143	422
Available-for-Sale Debt Securities, Gross Unrealized Gains	43	43
Available-for-Sale Debt Securities, Gross Unrealized Losses		(3)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	$ 186	$ 462

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).

+ References

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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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-Publisher FASB
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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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