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Marketable Securities - Additional Information (Detail) - USD ($) $ in Millions | Aug. 31, 2019 | May 31, 2019
--- | --- | ---
Schedule of Available-for-sale Securities [Line Items] |  |
Available-for-sale securities, current | $ 9.3 | $ 8.6
Available-for-sale securities, long-term | 16.4 | 16.4
Equity securities | $ 97.9 |
Maximum |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments with unrealized loss, percentage of fair values less than original cost | 15.00% |
Trading Securities |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Securities held in relation to deferred compensation plan | $ 12.8 | $ 12.3

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