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Components of marketable securities (Details) $ in Thousands | 12 Months Ended
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May 31, 2020 USD ($)
Marketable Securities [Line Items] |
Amortized Cost | $ 276,850
Unrealized gains | 577
Unrealized Losses | (23)
Fair Value | 277,404
US Treasury Securities [Member] |
Marketable Securities [Line Items] |
Amortized Cost | 2,502
Unrealized gains | 30
Fair Value | 2,532
Commercial PaperAnd Corporate Bonds [Member] |
Marketable Securities [Line Items] |
Amortized Cost | 257,700
Unrealized gains | 347
Unrealized Losses | (23)
Fair Value | 258,024
Certificates of Deposit [Member] |
Marketable Securities [Line Items] |
Amortized Cost | 16,648
Unrealized gains | 200
Fair Value | $ 16,848

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