Significant Accounting Policies (Policies)	9 Months Ended
Jul. 31, 2018
Accounting Policies [Abstract]
Government Grants	Government Grants Ciena accounts for proceeds from government grants as a reduction of expense when there is reasonable assurance that Ciena has met the required conditions associated with the grant and that grant proceeds will be received. Grant benefits are recorded to the particular line item of the Condensed Consolidated Statement of Operations to which the grant activity relates.
Newly Issued Accounting Standards - Effective and Not Yet Effective	Newly Issued Accounting Standards - Effective In January 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2017-01 (“ASU 2017-01”), Business Combinations: Clarifying the Definition of a Business, which clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisition or disposal of assets or businesses. The amendments in this update provide a screen to determine when a set of assets is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set of assets is not a business. Ciena will evaluate the effect of the update at the time of any future acquisition or disposal. Ciena adopted ASU 2017-01 during the first quarter of fiscal 2018. In August 2017, the FASB issued ASU No. 2017-12 (“ASU 2017-12”), Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities, which improves the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements and make certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP. The amendments in this update better align an entity’s risk management activities and financial reporting for hedging relationships, through changes to both the designation and measurement guidance for qualifying hedging relationships and presentation of hedge results. Ciena adopted ASU 2017-12 during the first quarter of fiscal 2018. For hedges for which Ciena has elected to exclude the spot-forward difference from assessment of effectiveness, Ciena has elected to amortize the difference on a straight-line basis. Ciena will record amortization in earnings each period with an offsetting entry to other comprehensive income, and all changes in fair value over the term of the derivative in other comprehensive income. The application of this accounting standard did not have a material impact on Ciena’s Condensed Consolidated Financial Statements. In March 2016, the FASB issued ASU No. 2016-09 (“ASU 2016-09”), Improvements to Employee Share-Based Payment Accounting, which provides guidance on several aspects of accounting for share-based payment transactions, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification on the statement of cash flows. Ciena adopted ASU 2016-09 during the first quarter of fiscal 2018. In connection with the adoption of this guidance, Ciena recognized approximately $62.1 million of deferred tax assets related to previously unrecognized tax benefits. This was recorded as a cumulative-effect adjustment to retained earnings as of the beginning of the first quarter of fiscal 2018. Additionally, the consolidated statements of cash flows will include excess tax benefits as an operating activity, on a prospective basis as a result of the adoption. Finally, Ciena has elected to recognize forfeitures when they occur, rather than to estimate the impact of forfeitures when the award is granted. Accordingly, Ciena recognized approximately $0.8 million for this change through a cumulative effect adjustment recorded to opening retained earnings in the first quarter of fiscal 2018. Newly Issued Accounting Standards - Not Yet Effective In May 2014, the FASB issued ASU No. 2014-09 (“ASU 2014-09”), Revenue from Contracts with Customers (Topic 606), which provides guidance for revenue recognition. ASU 2014-09 affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets. ASU 2014-09 will supersede the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific guidance. ASU 2014-09 also supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition-Construction-Type and Production-Type Contracts. For multiple element software arrangements where vendor-specific objective evidence (“VSOE”) of undelivered maintenance does not exist, Ciena currently recognizes revenue for the entire arrangement over the maintenance term. The adoption of ASU 2014-09 will require Ciena to determine the stand alone selling price for each of the software and software-related deliverables at contract inception, and Ciena consequently expects certain software deliverables will be recognized at a point in time rather than over a period of time. Ciena also expects certain installation and deployment, and consulting and network design services, will be recognized over a period of time rather than at a point in time. Ciena has considered the impact of the guidance in Accounting Standards Codification (“ASC”) 340-40, Other Assets and Deferred Costs; Contracts with Customers, and the interpretations of the FASB Transition Resource Group for Revenue Recognition (TRG) with respect to capitalization and amortization of incremental costs of obtaining a contract. In conjunction with this interpretation, Ciena has elected to implement the practical expedient clause allowing for incremental costs to be recognized as an expense when incurred if the period of the asset recognition is one year or less, and amortized over the period of performance, if the period of the asset recognition is greater than one year. Ciena expects to implement ASU 2014-09 using the modified retrospective approach whereby the cumulative effect at adoption will be presented as an adjustment to the opening balance of retained earnings. The comparative information will not be restated and will continue to be reported under the accounting standards in effect for those periods. ASU 2014-09 will be effective for Ciena beginning in the first quarter of fiscal 2019. Ciena is continuing to evaluate other possible impacts of the adoption of this ASU on its Consolidated Financial Statements and disclosures. In February 2016, the FASB issued ASU No. 2016-02 (“ASU 2016-02”), Leases, which requires an entity to recognize assets and liabilities on the balance sheet for the rights and obligations created by leased assets and to provide additional disclosures. ASU 2016-02 is effective for Ciena beginning in the first quarter of fiscal 2020. Under current GAAP, the majority of Ciena’s leases for its properties are considered operating leases, and Ciena expects that the adoption of this ASU will require these leases to be classified as financing leases and to be recognized as assets and liabilities on Ciena’s balance sheet. Ciena is continuing to evaluate other possible impacts of the adoption of ASU 2016-02 on its Consolidated Financial Statements and disclosures. In August 2018, the FASB issued ASU No. 2018-09 (“ASU 2018-09”), Codification Improvements which does not prescribe any new accounting guidance, but instead makes minor improvements and clarifications of several different FASB Accounting Standards Codification areas based on comments and suggestions made by various stakeholders. Certain updates are applicable immediately while others provide for a transition period to adopt as part of the next fiscal year beginning after December 15, 2018. Ciena is currently evaluating this guidance to determine the impact it may have on the consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13 (“ASU 2018-13”), Fair Value Measurement (Topic 820): Disclosure Framework which modifies the disclosure requirements on fair value measurements. ASU 2018-13 is effective for Ciena beginning in the first quarter of fiscal year 2020, early adoption is permitted. Ciena is currently evaluating this guidance to determine the impact on its disclosures. In August 2018, the FASB issued ASU No. 2018-14 (“ASU 2018-14”), Compensation -Retirement Benefits - Defined Benefit Plans which modifies the disclosure requirements on company-sponsored defined benefit plans. ASU 2018-14 is effective for Ciena beginning in the first quarter of fiscal year 2021, early adoption is permitted. Ciena is currently evaluating this guidance to determine the impact on its disclosures. In August 2018, the FASB issued ASU No. 2018-15 (“ASU 2018-15”), Intangibles - Goodwill and Other-Internal-Use Software which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 is effective for Ciena beginning in the first quarter of fiscal year 2020, early adoption is permitted. Ciena is currently evaluating this guidance to determine the impact on its disclosures.

Newly Issued Accounting Standards - Effective

In January 2017, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2017-01 (“ASU 2017-01”), Business Combinations: Clarifying the Definition of a Business, which clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisition or disposal of assets or businesses. The amendments in this update provide a screen to determine when a set of assets is not a business. The screen requires that when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, the set of assets is not a business. Ciena will evaluate the effect of the update at the time of any future acquisition or disposal. Ciena adopted ASU 2017-01 during the first quarter of fiscal 2018.

In August 2017, the FASB issued ASU No. 2017-12 (“ASU 2017-12”), Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities, which improves the financial reporting of hedging relationships to better portray the economic results of an entity’s risk management activities in its financial statements and make certain targeted improvements to simplify the application of the hedge accounting guidance in current GAAP. The amendments in this update better align an entity’s risk management activities and financial reporting for hedging relationships, through changes to both the designation and measurement guidance for qualifying hedging relationships and presentation of hedge results. Ciena adopted ASU 2017-12 during the first quarter of fiscal 2018. For hedges for which Ciena has elected to exclude the spot-forward difference from assessment of effectiveness, Ciena has elected to amortize the difference on a straight-line basis. Ciena will record amortization in earnings each period with an offsetting entry to other comprehensive income, and all changes in fair value over the term of the derivative in other comprehensive income. The application of this accounting standard did not have a material impact on Ciena’s Condensed Consolidated Financial Statements.

In March 2016, the FASB issued ASU No. 2016-09 (“ASU 2016-09”), Improvements to Employee Share-Based Payment Accounting, which provides guidance on several aspects of accounting for share-based payment transactions, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification on the statement of cash flows. Ciena adopted ASU 2016-09 during the first quarter of fiscal 2018. In connection with the adoption of this guidance, Ciena recognized approximately $62.1 million of deferred tax assets related to previously unrecognized tax benefits. This was recorded as a cumulative-effect adjustment to retained earnings as of the beginning of the first quarter of fiscal 2018. Additionally, the consolidated statements of cash flows will include excess tax benefits as an operating activity, on a prospective basis as a result of the adoption. Finally, Ciena has elected to recognize forfeitures when they occur, rather than to estimate the impact of forfeitures when the award is granted. Accordingly, Ciena recognized approximately $0.8 million for this change through a cumulative effect adjustment recorded to opening retained earnings in the first quarter of fiscal 2018.

Newly Issued Accounting Standards - Not Yet Effective

In May 2014, the FASB issued ASU No. 2014-09 (“ASU 2014-09”), Revenue from Contracts with Customers (Topic 606), which provides guidance for revenue recognition. ASU 2014-09 affects any entity that either enters into contracts with customers to transfer goods or services or enters into contracts for the transfer of non-financial assets. ASU 2014-09 will supersede the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific guidance. ASU 2014-09 also supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition-Construction-Type and Production-Type Contracts.

For multiple element software arrangements where vendor-specific objective evidence (“VSOE”) of undelivered maintenance does not exist, Ciena currently recognizes revenue for the entire arrangement over the maintenance term. The adoption of ASU 2014-09 will require Ciena to determine the stand alone selling price for each of the software and software-related deliverables at contract inception, and Ciena consequently expects certain software deliverables will be recognized at a point in time rather than over a period of time.

Ciena also expects certain installation and deployment, and consulting and network design services, will be recognized over a period of time rather than at a point in time.

Ciena has considered the impact of the guidance in Accounting Standards Codification (“ASC”) 340-40, Other Assets and Deferred Costs; Contracts with Customers, and the interpretations of the FASB Transition Resource Group for Revenue Recognition (TRG) with respect to capitalization and amortization of incremental costs of obtaining a contract. In conjunction with this interpretation, Ciena has elected to implement the practical expedient clause allowing for incremental costs to be recognized as an expense when incurred if the period of the asset recognition is one year or less, and amortized over the period of performance, if the period of the asset recognition is greater than one year.

Ciena expects to implement ASU 2014-09 using the modified retrospective approach whereby the cumulative effect at adoption will be presented as an adjustment to the opening balance of retained earnings. The comparative information will not be restated and will continue to be reported under the accounting standards in effect for those periods. ASU 2014-09 will be effective for Ciena beginning in the first quarter of fiscal 2019. Ciena is continuing to evaluate other possible impacts of the adoption of this ASU on its Consolidated Financial Statements and disclosures.

In February 2016, the FASB issued ASU No. 2016-02 (“ASU 2016-02”), Leases, which requires an entity to recognize assets and liabilities on the balance sheet for the rights and obligations created by leased assets and to provide additional disclosures. ASU 2016-02 is effective for Ciena beginning in the first quarter of fiscal 2020. Under current GAAP, the majority of Ciena’s leases for its properties are considered operating leases, and Ciena expects that the adoption of this ASU will require these leases to be classified as financing leases and to be recognized as assets and liabilities on Ciena’s balance sheet. Ciena is continuing to evaluate other possible impacts of the adoption of ASU 2016-02 on its Consolidated Financial Statements and disclosures.

In August 2018, the FASB issued ASU No. 2018-09 (“ASU 2018-09”), Codification Improvements which does not prescribe any new accounting guidance, but instead makes minor improvements and clarifications of several different FASB Accounting Standards Codification areas based on comments and suggestions made by various stakeholders. Certain updates are applicable immediately while others provide for a transition period to adopt as part of the next fiscal year beginning after December 15, 2018. Ciena is currently evaluating this guidance to determine the impact it may have on the consolidated financial statements.

In August 2018, the FASB issued ASU No. 2018-13 (“ASU 2018-13”), Fair Value Measurement (Topic 820): Disclosure Framework which modifies the disclosure requirements on fair value measurements. ASU 2018-13 is effective for Ciena beginning in the first quarter of fiscal year 2020, early adoption is permitted. Ciena is currently evaluating this guidance to determine the impact on its disclosures.

In August 2018, the FASB issued ASU No. 2018-14 (“ASU 2018-14”), Compensation -Retirement Benefits - Defined Benefit Plans which modifies the disclosure requirements on company-sponsored defined benefit plans. ASU 2018-14 is effective for Ciena beginning in the first quarter of fiscal year 2021, early adoption is permitted. Ciena is currently evaluating this guidance to determine the impact on its disclosures.

In August 2018, the FASB issued ASU No. 2018-15 (“ASU 2018-15”), Intangibles - Goodwill and Other-Internal-Use Software which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. ASU 2018-15 is effective for Ciena beginning in the first quarter of fiscal year 2020, early adoption is permitted. Ciena is currently evaluating this guidance to determine the impact on its disclosures.