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INCOME TAXES (Details) $ in Millions | 3 Months Ended
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Jul. 31, 2021 USD ($)
Income Tax Disclosure [Abstract] |
Intra-entity transfer of non-US intellectual property rights, income tax benefit | $ (124.2)

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- Definition Effective Income Tax Rate Reconciliation, Intra-Entity Transfer Of Foreign Intellectual Property Rights, Amount + References No definition available. + Details
Name: | cien_EffectiveIncomeTaxRateReconciliationIntraEntityTransferOfForeignIntellectualPropertyRightsAmount
Namespace Prefix: | cien_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration