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Summary of Available-for-Sale Marketable Securities by Asset Type (Detail) - USD ($) $ in Thousands | Aug. 31, 2019 | May 31, 2019
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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

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- Definition 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). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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- Definition 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 Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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- Definition 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 -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 + Details
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