Summary of Available-for-Sale Marketable Securities by Asset Type (Detail) - USD ($) $ in Thousands	Aug. 31, 2019	May 31, 2019
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	$ 25,254	$ 24,905
Available-for-Sale Debt Securities, Gross Unrealized Gains	603	415
Available-for-Sale Debt Securities, Gross Unrealized Losses	(124)	(311)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	25,733	25,009
U.S. Treasury and other government
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	24,832	24,483
Available-for-Sale Debt Securities, Gross Unrealized Gains	546	372
Available-for-Sale Debt Securities, Gross Unrealized Losses	(124)	(308)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	25,254	24,547
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Available-for-Sale Debt Securities, Amortized Cost	422	422
Available-for-Sale Debt Securities, Gross Unrealized Gains	57	43
Available-for-Sale Debt Securities, Gross Unrealized Losses		(3)
Available-for-Sale Debt Securities, Fair Value (Net Carrying Amount)	$ 479	$ 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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-Section 50
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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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