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Financial Instruments - Additional Information (Detail) - USD ($) | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Oct. 31, 2020 | Oct. 31, 2019 | Oct. 31, 2020 | Oct. 31, 2019 | Apr. 30, 2020
Financial Instrument [Line Items] |  |  |  |  |
Sale/maturities of available-for-sale marketable securities | $ 16,700,000 | $ 0 | $ 28,400,000 | $ 0 |
Unrealized loss relates to equity securities |  |  |  |  | $ 8,200,000
Unrealized gains relates to equity securities |  |  | 11,200,000 |  |
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts |  |  |  |  |
Financial Instrument [Line Items] |  |  |  |  |
Foreign currency gains (losses) | (500,000) | $ 2,100,000 | 300,000 | $ 500,000 |
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts | Income Taxes And Other Receivables | Derivatives Purchased |  |  |  |  |
Financial Instrument [Line Items] |  |  |  |  |
Derivative notional amount | 85,100,000 |  | 85,100,000 |  | 91,200,000
Not Designated as Hedge Instrument | Foreign Exchange Forward Contracts | Income Taxes And Other Receivables | Derivatives Sold |  |  |  |  |
Financial Instrument [Line Items] |  |  |  |  |
Derivative notional amount | $ 49,200,000 |  | $ 49,200,000 |  | $ 41,800,000
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 |  |  | 12 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=121590274&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=121590274&loc=SL5624171-113959 + Details
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- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959 + Details
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- Definition Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117546-209714 + Details
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- Definition Amount of cash inflow from sale, maturity, prepayment and call 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 230 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3151-108585 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3179-108585 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26853-111562 + Details
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