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Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Jul. 31, 2021 | Jul. 31, 2020 | Apr. 30, 2021
Financial Instrument [Line Items] |  |  |
Sale/maturities of available-for-sale marketable securities | $ 21.7 | $ 11.8 |
Unrealized gains relates to equity securities | 4.1 | 11.4 |
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts |  |  |
Financial Instrument [Line Items] |  |  |
Foreign currency gains (losses) | 0.1 | $ 0.8 |
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts | Income Taxes And Other Receivables | Derivatives Purchased |  |  |
Financial Instrument [Line Items] |  |  |
Derivative notional amount | 79.7 |  | $ 69.4
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts | Income Taxes And Other Receivables | Derivatives Sold |  |  |
Financial Instrument [Line Items] |  |  |
Derivative notional amount | $ 45.4 |  | $ 44.9
Available-for-sale Marketable Securities | Minimum |  |  |
Financial Instrument [Line Items] |  |  |
Marketable securities remaining maturity | 1 month |  |
Available-for-sale Marketable Securities | Maximum |  |  |
Financial Instrument [Line Items] |  |  |
Marketable securities remaining maturity | 22 months |  |

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- Definition Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CC -URI http://asc.fasb.org/extlink&oid=125515794&loc=SL109998890-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959 + Details
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