Ciena (CIEN) 10-Q 6 Jun 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Apr. 30, 2018	Jun. 04, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	CIENA CORP
Entity Central Index Key	936,395
Current Fiscal Year End Date	--10-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Apr. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		142,827,652

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Revenue:
Products	$ 604,226	$ 584,630	$ 1,129,835	$ 1,091,623
Services	125,752	122,392	246,278	236,896
Total revenue	729,978	707,022	1,376,113	1,328,519
Cost of goods sold:
Products	372,568	327,295	685,688	614,106
Services	64,103	61,487	125,353	122,388
Total cost of goods sold	436,671	388,782	811,041	736,494
Gross profit	293,307	318,240	565,072	592,025
Operating expenses:
Research and development	116,924	121,623	235,448	238,492
Selling and marketing	97,359	88,551	185,874	173,553
General and administrative	38,976	34,990	77,382	70,854
Amortization of intangible assets	3,623	10,980	7,246	25,531
Significant asset impairments and restructuring costs	4,359	4,276	10,320	6,671
Total operating expenses	261,241	260,420	516,270	515,101
Income from operations	32,066	57,820	48,802	76,924
Interest and other income (loss), net	1,296	(2,918)	2,871	(2,548)
Interest expense	(13,031)	(13,308)	(26,765)	(28,511)
Income before income taxes	20,331	41,594	24,908	45,865
Provision for income taxes	6,475	3,568	484,415	3,978
Net income (loss)	$ 13,856	$ 38,026	$ (459,507)	$ 41,887
Basic net income (loss) per common share (in dollars per share)	$ 0.10	$ 0.27	$ (3.19)	$ 0.30
Diluted net income (loss) per potential common share (in dollars per share)	$ 0.09	$ 0.25	$ (3.19)	$ 0.29
Weighted average basic common shares outstanding (in shares)	143,975	141,743	143,948	141,223
Weighted average dilutive potential common shares outstanding (in shares)	147,973	165,273	143,948	147,842

Condensed Consolidated Stateme3

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Net income (loss)	$ 13,856	$ 38,026	$ (459,507)	$ 41,887
Change in unrealized loss on available-for-sale securities, net of tax	(76)	(278)	(337)	(527)
Change in cumulative translation adjustments	(7,133)	(2,243)	1,069	(1,753)
Other comprehensive income	(7,447)	(3,015)	5,945	3,143
Total comprehensive income (loss)	6,409	35,011	(453,562)	45,030
Change in unrealized gain on foreign currency forward contracts, net of tax
Change in unrealized gain on foreign currency forward contracts and forward starting interest rate swaps, net of tax	(2,537)	(899)	(35)	526
Change in unrealized gain on forward starting interest rate swap, net of tax
Change in unrealized gain on foreign currency forward contracts and forward starting interest rate swaps, net of tax	$ 2,299	$ 405	$ 5,248	$ 4,897

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Current assets:
Cash and cash equivalents	$ 652,096	$ 640,513
Short-term investments	268,584	279,133
Accounts receivable, net of allowance for doubtful accounts of $17.7 million and $17.6 million as of April 30, 2018 and October 31, 2017, respectively.	647,380	622,183
Inventories	231,338	267,143
Prepaid expenses and other	186,024	197,339
Total current assets	1,985,422	2,006,311
Long-term investments	58,895	49,783
Equipment, building, furniture and fixtures, net	298,631	308,465
Goodwill	267,442	267,458
Other intangible assets, net	90,573	100,997
Deferred tax asset, net	734,824	1,155,104
Other long-term assets	70,767	63,593
Total assets	3,506,554	3,951,711
Current liabilities:
Accounts payable	264,398	260,098
Accrued liabilities and other short-term obligations	270,231	322,934
Deferred revenue	101,918	102,418
Current portion of long-term debt	353,208	352,293
Total current liabilities	989,755	1,037,743
Long-term deferred revenue	76,725	82,589
Other long-term obligations	110,417	111,349
Long-term debt, net	585,538	583,688
Total liabilities	1,762,435	1,815,369
Commitments and contingencies (Note 17)
Stockholders’ equity:
Preferred stock – par value $0.01; 20,000,000 shares authorized; zero shares issued and outstanding	0	0
Common stock – par value $0.01; 290,000,000 shares authorized; 143,427,976 and 143,043,227 shares issued and outstanding	1,434	1,430
Additional paid-in capital	6,810,226	6,810,182
Accumulated other comprehensive income (loss)	(5,072)	(11,017)
Accumulated deficit	(5,062,469)	(4,664,253)
Total stockholders’ equity	1,744,119	2,136,342
Total liabilities and stockholders’ equity	$ 3,506,554	$ 3,951,711

Condensed Consolidated Balance5

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Apr. 30, 2018	Oct. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 17.7	$ 17.6
Stockholders’ equity:
Preferred stock par value per share (in dollars per share)	$ 0.01	$ 0.01
Preferred stock shares authorized (in shares)	20,000,000	20,000,000
Preferred stock shares issued (in shares)	0	0
Preferred stock shares outstanding (in shares)	0	0
Common stock par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock shares authorized (in shares)	290,000,000	290,000,000
Common stock shares issued (in shares)	143,427,976	143,043,227
Common stock shares outstanding (in shares)	143,427,976	143,043,227

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Cash flows provided by operating activities:
Net income (loss)	$ (459,507)	$ 41,887
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of equipment, building, furniture and fixtures, and amortization of leasehold improvements	41,400	35,548
Share-based compensation costs	26,559	24,830
Amortization of intangible assets	11,824	33,466
Deferred tax provision	481,401	0
Provision for inventory excess and obsolescence	14,977	19,623
Provision for warranty	10,565	2,347
Other	12,645	10,416
Changes in assets and liabilities:
Accounts receivable	(28,055)	9,381
Inventories	20,420	(95,554)
Prepaid expenses and other	2,623	(15,054)
Accounts payable, accruals and other obligations	(55,986)	(24,974)
Deferred revenue	(5,736)	3,832
Net cash provided by operating activities	73,130	45,748
Cash flows used in investing activities:
Payments for equipment, furniture, fixtures and intellectual property	(31,946)	(60,328)
Restricted cash	54	0
Purchase of available for sale securities	(198,026)	(179,833)
Proceeds from maturities of available for sale securities	200,000	180,000
Settlement of foreign currency forward contracts, net	132	(2,965)
Purchase of cost method investment	(767)	0
Net cash used in investing activities	(30,553)	(63,126)
Cash flows used in financing activities:
Payment of long-term debt	(2,000)	(47,296)
Payment for modification of term loans	0	(93,625)
Payment of capital lease obligations	(1,868)	(1,528)
Repurchases of common stock-repurchase program	(38,036)	0
Proceeds from issuance of common stock	11,804	10,345
Net cash used in financing activities	(30,100)	(132,104)
Effect of exchange rate changes on cash and cash equivalents	(894)	490
Net increase (decrease) in cash and cash equivalents	11,583	(148,992)
Cash and cash equivalents at beginning of period	640,513	777,615
Cash and cash equivalents at end of period	652,096	628,623
Supplemental disclosure of cash flow information
Cash paid during the period for interest	21,843	23,439
Cash paid during the period for income taxes, net	15,136	11,379
Non-cash investing activities
Purchase of equipment in accounts payable	3,226	3,818
Building subject to capital lease	0	20,695
Non-cash financing activities
Repurchase of common stock in accrued liabilities from repurchase program	$ 1,111	$ 0

Condensed Consolidated Stateme7

Condensed Consolidated Statement of Changes in Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in-Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Oct. 31, 2016		139,767,627
Beginning balance at Oct. 31, 2016	$ 766,341	$ 1,398	$ 6,715,478	$ (24,329)	$ (5,926,206)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	41,887				41,887
Other comprehensive income	3,143			3,143
Issuance of shares from employee equity plans (in shares)		2,000,821
Issuance of shares from employee equity plans	10,345	$ 20	10,325
Share-based compensation expense	24,830		24,830
Ending balance (in shares) at Apr. 30, 2017		141,768,448
Ending balance at Apr. 30, 2017	846,546	$ 1,418	6,750,633	(21,186)	(5,884,319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of adoption of new accounting standard	$ 62,123		832		61,291
Beginning balance (in shares) at Oct. 31, 2017	143,043,227	143,043,227
Beginning balance at Oct. 31, 2017	$ 2,136,342	$ 1,430	6,810,182	(11,017)	(4,664,253)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(459,507)				(459,507)
Other comprehensive income	$ 5,945			5,945
Repurchase of common stock (in shares)	(1,627,233)	(1,627,233)
Repurchase of common stock	$ (39,147)	$ (16)	(39,131)
Issuance of shares from employee equity plans (in shares)		2,011,982
Issuance of shares from employee equity plans	11,804	$ 20	11,784
Share-based compensation expense	$ 26,559		26,559
Ending balance (in shares) at Apr. 30, 2018	143,427,976	143,427,976
Ending balance at Apr. 30, 2018	$ 1,744,119	$ 1,434	$ 6,810,226	$ (5,072)	$ (5,062,469)

Interim Financial Statements

Interim Financial Statements	6 Months Ended
	Apr. 30, 2018
Quarterly Financial Data [Abstract]
Interim Financial Statements	INTERIM FINANCIAL STATEMENTS The interim financial statements included herein for Ciena Corporation and its wholly owned subsidiaries (“Ciena”) have been prepared by Ciena, without audit, pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (the "SEC"). In the opinion of management, the financial statements included in this report reflect all normal recurring adjustments that Ciena considers necessary for the fair statement of the results of operations for the interim periods covered and of the financial position of Ciena at the date of the interim balance sheets. Certain information and footnote disclosures normally included in the annual financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") have been condensed or omitted pursuant to such rules and regulations. The Condensed Consolidated Balance Sheet as of October 31, 2017 was derived from audited financial statements, but does not include all disclosures required by GAAP. However, Ciena believes that the disclosures are adequate to understand the information presented herein. The operating results for interim periods are not necessarily indicative of the operating results for the entire year. These financial statements should be read in conjunction with Ciena’s audited consolidated financial statements and the notes thereto included in Ciena’s annual report on Form 10-K for the fiscal year ended October 31, 2017 . Ciena has a 52 or 53-week fiscal year, with quarters ending on the Saturday nearest to the last day of January, April, July and October, respectively, of each year. Fiscal 2018 is a 53-week fiscal year with the additional week occurring in the fourth quarter. Fiscal 2017 was a 52-week fiscal year. For purposes of financial statement presentation, each fiscal year is described as having ended on October 31, and the fiscal quarters are described as having ended on January 31, April 30 and July 31 of each fiscal year.

Significant Accounting Policies

Significant Accounting Policies	6 Months Ended
	Apr. 30, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	SIGNIFICANT ACCOUNTING POLICIES Except for the changes in certain policies described below, there have been no material changes to Ciena's significant accounting policies, compared to the accounting policies described in Note 1, Ciena Corporation and Significant Accounting Policies and Estimates, in Notes to Consolidated Financial Statements in Item 8 of Part II of Ciena's annual report on Form 10-K for the fiscal year ended October 31, 2017. Government Grants Ciena accounts for proceeds from government grants as a reduction of expense when there is reasonable assurance that Ciena has complied with the conditions attached to the grant and that grant proceeds will be received. Grant benefits are recorded to the line item in the Condensed Consolidated Statement of Operations to which the grant activity relates. See Note 17 below. 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. Ciena expects that the adoption of ASU 2014-09 will require that it 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.

Restructuring Costs

Restructuring Costs	6 Months Ended
	Apr. 30, 2018
Restructuring and Related Activities [Abstract]
Restructuring Costs	RESTRUCTURING COSTS Ciena has undertaken a number of restructuring activities intended to reduce expense and to better align its workforce and costs with market opportunities, product development and business strategies. The following table sets forth the restructuring activity and balance of the restructuring liability accounts for the six months ended April 30, 2018 (in thousands): Workforce reduction Consolidation of excess facilities Total Balance at October 31, 2017 $ 1,291 $ 1,648 $ 2,939 Additional liability recorded 8,232 (1) 2,088 (2) 10,320 Cash payments (8,211 ) (1,896 ) (10,107 ) Balance at April 30, 2018 $ 1,312 $ 1,840 $ 3,152 Current restructuring liabilities $ 1,312 $ 865 $ 2,177 Non-current restructuring liabilities $ — $ 975 $ 975 (1) Reflects a global workforce reduction of approximately 150 employees during fiscal 2018 as part of a business optimization strategy to improve gross margin, constrain operating expense and redesign certain business processes. (2) Reflects unfavorable lease commitments in connection with a portion of facilities located in Petaluma, California. The following table sets forth the restructuring activity and balance of the restructuring liability accounts for the six months ended April 30, 2017 (in thousands): Workforce reduction Consolidation of excess facilities Total Balance at October 31, 2016 $ 868 $ 1,970 $ 2,838 Additional liability recorded 2,369 (1) 4,302 (2) 6,671 Cash payments (3,084 ) (1,133 ) (4,217 ) Balance at April 30, 2017 $ 153 $ 5,139 $ 5,292 Current restructuring liabilities $ 153 $ 4,928 $ 5,081 Non-current restructuring liabilities $ — $ 211 $ 211 (1) Reflects a global workforce reduction of approximately 50 employees during the first quarter of fiscal 2017 as part of a business optimization strategy to improve gross margin, constrain operating expense and redesign certain business processes and systems. (2) Reflects unfavorable lease commitments and relocation costs incurred during the second quarter of fiscal 2017 in connection with the facility transition from Ciena's existing research and development center located at Lab 10 on the former Nortel Carling Campus to a new campus facility in Ottawa, Canada.

Interest and Other Income (Loss

Interest and Other Income (Loss), Net	6 Months Ended
	Apr. 30, 2018
Other Income and Expenses [Abstract]
Interest and Other Income (Loss), Net	INTEREST AND OTHER INCOME (LOSS), NET The components of interest and other income (loss), net, are as follows (in thousands): Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Interest income $ 3,212 $ 1,507 $ 5,656 $ 2,789 Gains (losses) on non-hedge designated foreign currency forward contracts 2,868 (2,749 ) 2,169 (1,725 ) Foreign currency exchange gain (loss) (4,804 ) 1,292 (4,791 ) (1,125 ) Modification of term loan — (2,924 ) — (2,924 ) Other 20 (44 ) (163 ) 437 Interest and other income (loss), net $ 1,296 $ (2,918 ) $ 2,871 $ (2,548 ) Ciena Corporation, as the U.S. parent entity, uses the U.S. Dollar as its functional currency; however, some of its foreign branch offices and subsidiaries use local currencies as their functional currencies. Ciena recorded $4.8 million and $1.1 million in foreign currency exchange rate losses during the first six months of fiscal 2018 and fiscal 2017 , respectively, as a result of monetary assets and liabilities that were transacted in a currency other than the entity's functional currency, and the remeasurement adjustments were recorded in interest and other income (loss), net on the Condensed Consolidated Statements of Operations. From time to time, Ciena uses foreign currency forwards to hedge these balance sheet exposures. These forwards are not designated as hedges for accounting purposes, and any net gain or loss associated with these derivatives is reported in interest and other income (loss), net on the Condensed Consolidated Statements of Operations. During the first six months of fiscal 2018 , Ciena recorded gains of $2.2 million from non-hedge designated foreign currency forward contracts. During the first six months of fiscal 2017 , Ciena recorded losses of $1.7 million from non-hedge designated foreign currency forward contracts.

Income Taxes

Income Taxes	6 Months Ended
	Apr. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES On December 22, 2017, the Tax Cuts and Jobs Act (the "Tax Act") was enacted. The Tax Act significantly revises the U.S. corporate income tax by, among other things, lowering the statutory corporate income tax rate (“federal tax rate”) from 35% to 21% effective January 1, 2018, implementing a modified territorial tax system, and imposing a mandatory one-time transition tax on accumulated earnings of foreign subsidiaries that were previously tax deferred. As a fiscal-year taxpayer, certain provisions of the Tax Act impact Ciena in fiscal 2018, including the change in the federal tax rate and the one-time transition tax, while other provisions will be effective at the beginning of fiscal 2019, including the implementation of a modified territorial tax system, other changes to how foreign earnings are subject to U.S. tax, and adoption of an alternative tax system. As a result of the decrease in the federal tax rate from 35% to 21% effective January 1, 2018, Ciena has computed its income tax expense for the October 31, 2018 fiscal year using a blended federal tax rate of 23.4% . The 21% federal tax rate is expected to apply to Ciena’s fiscal year ending October 31, 2019 and each year thereafter. Ciena remeasured its deferred tax assets and liabilities ("DTA") using the federal tax rate that will apply when the related temporary differences are expected to reverse. During the six months ended April 30, 2018 , Ciena recorded a provisional tax expense of $484.4 million , primarily related to the Tax Act and consisted of the following: a $431.3 million charge related to the remeasurement of U.S. net deferred tax assets at the lower statutory rate under the Tax Act and a $45.6 million charge related to a transition tax on accumulated historical foreign earnings and its deemed repatriation to the U.S. In December 2017, the SEC issued Staff Accounting Bulletin No. 118, which addresses how a company recognizes provisional amounts when it does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete its accounting for the effect of the changes due to the Tax Act. The measurement period ends when a company has obtained, prepared and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year. The final impact of the Tax Act may differ from the above provisional amounts due to changes in interpretations of the Tax Act, legislative action to address questions that arise because of the Tax Act, changes in accounting standards for income taxes and related interpretations in response to the Tax Act, and any updates or changes to estimates used in the provisional amounts. Ciena has determined that the $45.6 million of tax expense for the U.S. transition tax on accumulated earnings of foreign subsidiaries and the $431.3 million of tax expense for DTA remeasurement were each provisional amounts and reasonable estimates as of April 30, 2018 . Estimates used in the provisional amounts include the anticipated reversal pattern of the gross DTA plus the earnings and profits, cash position at the end of fiscal year 2018, foreign taxes and withholding taxes attributable to foreign subsidiaries. Ciena currently intends to reinvest indefinitely its foreign earnings outside the U.S. However, Ciena intends to further study changes enacted by the Tax Act, costs of repatriation and the current and future cash needs of foreign operations to determine whether there is an opportunity to repatriate these earnings in the future on a tax-efficient basis. If Ciena determines to repatriate these earnings, the provisional amount of unrecognized deferred income tax liability related to these foreign withholding taxes would be approximately $24.0 million . There are no other significant temporary differences for which a deferred tax liability has not been recognized. The significant components of DTA are as follows (in thousands): April 30, October 31, 2018 2017 Deferred tax assets: Reserves and accrued liabilities $ 36,115 $ 56,597 Depreciation and amortization 288,145 451,385 NOL and credit carry forward 538,869 803,622 Other 18,706 29,398 Gross deferred tax assets 881,835 1,341,002 Valuation allowance (147,011 ) (185,898 ) Deferred tax asset, net of valuation allowance $ 734,824 $ 1,155,104 In connection with the adoption of ASU 2016-09, 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. See Note 2 above and Note 14 below. As of April 30, 2018 , Ciena continues to maintain a valuation allowance of $147.0 million . This valuation allowance is primarily related to state and foreign net operating losses and credits that Ciena estimates it will not be able to use.

Short-Term and Long-Term Invest

Short-Term and Long-Term Investments	6 Months Ended
	Apr. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Short-Term and Long-Term Investments	SHORT-TERM AND LONG-TERM INVESTMENTS As of the dates indicated, investments are comprised of the following (in thousands): April 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. government obligations: Included in short-term investments $ 239,291 $ — (601 ) $ 238,690 Included in long-term investments 59,066 — (171 ) 58,895 $ 298,357 $ — $ (772 ) $ 297,585 Commercial paper: Included in short-term investments $ 29,892 2 — $ 29,894 $ 29,892 $ 2 $ — $ 29,894 October 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. government obligations: Included in short-term investments $ 249,498 $ — $ (305 ) $ 249,193 Included in long-term investments 49,910 — (127 ) 49,783 $ 299,408 $ — $ (432 ) $ 298,976 Commercial paper: Included in short-term investments $ 29,939 1 — $ 29,940 $ 29,939 $ 1 $ — $ 29,940 The following table summarizes the final legal maturities of debt investments at April 30, 2018 (in thousands): Amortized Cost Estimated Fair Value Less than one year $ 269,183 $ 268,584 Due in 1-2 years 59,066 58,895 $ 328,249 $ 327,479

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Apr. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS As of the date indicated, the following table summarizes the assets and liabilities that are recorded at fair value on a recurring basis (in thousands): April 30, 2018 Level 1 Level 2 Total Assets: Money market funds $ 476,187 $ — $ 476,187 U.S. government obligations — 297,585 297,585 Commercial paper — 99,745 99,745 Foreign currency forward contracts — 97 97 Forward starting interest rate swaps — 6,333 6,333 Total assets measured at fair value $ 476,187 $ 403,760 $ 879,947 Liabilities: Foreign currency forward contracts $ — $ 1,317 $ 1,317 Total liabilities measured at fair value $ — $ 1,317 $ 1,317 October 31, 2017 Level 1 Level 2 Total Assets: Money market funds $ 511,355 $ — $ 511,355 U.S. government obligations — 298,976 298,976 Commercial paper — 89,865 89,865 Foreign currency forward contracts — 227 227 Forward starting interest rate swaps — 218 218 Total assets measured at fair value $ 511,355 $ 389,286 $ 900,641 Liabilities: Foreign currency forward contracts $ — $ 2,129 $ 2,129 Total liabilities measured at fair value $ — $ 2,129 $ 2,129 As of the date indicated, the assets and liabilities above are presented on Ciena’s Condensed Consolidated Balance Sheet as follows (in thousands): April 30, 2018 Level 1 Level 2 Total Assets: Cash equivalents $ 476,187 $ 69,851 $ 546,038 Short-term investments — 268,584 268,584 Prepaid expenses and other — 97 97 Long-term investments — 58,895 58,895 Other long-term assets — 6,333 6,333 Total assets measured at fair value $ 476,187 $ 403,760 $ 879,947 Liabilities: Accrued liabilities $ — $ 1,317 $ 1,317 Total liabilities measured at fair value $ — $ 1,317 $ 1,317 October 31, 2017 Level 1 Level 2 Total Assets: Cash equivalents $ 511,355 $ 59,925 $ 571,280 Short-term investments — 279,133 279,133 Prepaid expenses and other — 227 227 Long-term investments — 49,783 49,783 Other long-term assets — 218 218 Total assets measured at fair value $ 511,355 $ 389,286 $ 900,641 Liabilities: Accrued liabilities $ — $ 2,129 $ 2,129 Total liabilities measured at fair value $ — $ 2,129 $ 2,129 Ciena did not have any transfers between Level 1 and Level 2 fair value measurements during the periods presented.

Inventories

Inventories	6 Months Ended
	Apr. 30, 2018
Inventory Disclosure [Abstract]
Inventories	INVENTORIES As of the dates indicated, inventories are comprised of the following (in thousands): April 30, October 31, Raw materials $ 48,356 $ 52,898 Work-in-process 13,253 18,623 Finished goods 165,733 185,488 Deferred cost of goods sold 55,161 61,340 282,503 318,349 Provision for excess and obsolescence (51,165 ) (51,206 ) $ 231,338 $ 267,143 Ciena writes down its inventory for estimated obsolescence or unmarketable inventory by an amount equal to the difference between the cost of inventory and the estimated net realizable value based on assumptions about future demand and market conditions. During the first six months of fiscal 2018 , Ciena recorded a provision for excess and obsolescence of $15.0 million , primarily related to a decrease in the forecasted demand for certain Networking Platforms products. Deductions from the provision for excess and obsolete inventory relate primarily to disposal activities.

Accrued Liabilities and Other S

Accrued Liabilities and Other Short-Term Obligations	6 Months Ended
	Apr. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Accrued Liabilities and Other Short-Term Obligations	ACCRUED LIABILITIES AND OTHER SHORT-TERM OBLIGATIONS As of the dates indicated, accrued liabilities and other short-term obligations are comprised of the following (in thousands): April 30, October 31, Compensation, payroll related tax and benefits (1) $ 78,744 $ 113,272 Warranty 43,392 42,456 Vacation 42,744 39,778 Capital lease obligations 3,828 3,772 Interest payable 3,602 3,612 Other 97,921 120,044 $ 270,231 $ 322,934 (1) Reduction is primarily due to the timing of bonus payments to employees under Ciena's annual cash incentive compensation plan. The following table summarizes the activity in Ciena’s accrued warranty for the fiscal periods indicated (in thousands): Six Months Ended April 30, Beginning Balance Current Period Provisions (1) Settlements Ending Balance 2017 $ 52,324 2,347 (8,646 ) $ 46,025 2018 $ 42,456 10,565 (9,629 ) $ 43,392 (1) As a result of lower than expected actual failure rates, Ciena adjusted its fiscal 2017 provision for warranty. This adjustment had the effect of reducing warranty provision by $6.3 million for the six months ended April 30, 2017 .

Derivative Instruments

Derivative Instruments	6 Months Ended
	Apr. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS Foreign Currency Derivatives As of April 30, 2018 and October 31, 2017 , Ciena had forward contracts to hedge its foreign exchange exposure in order to reduce the variability in its Canadian Dollar and Indian Rupee denominated expense, which principally relates to research and development activities, and its Euro denominated revenue. The notional amount of these contracts was approximately $114.2 million and $86.1 million as of April 30, 2018 and October 31, 2017 , respectively. These foreign exchange contracts have maturities of 12 months or less and have been designated as cash flow hedges. During the first six months of fiscal 2018 and fiscal 2017 , in order to hedge certain balance sheet exposures, Ciena entered into forward contracts to mitigate risk due to volatility in the Brazilian Real, Canadian Dollar and Mexican Peso. The notional amount of these contracts was approximately $92.5 million and $83.4 million as of April 30, 2018 and October 31, 2017 , respectively. These foreign exchange contracts have maturities of 12 months or less and have not been designated as hedges for accounting purposes. Interest Rate Derivatives Ciena is exposed to floating rates of LIBOR interest on its term loan borrowings (see Note 12 below) and has hedged such risk by entering into floating to fixed interest rate swap arrangements ("interest rate swaps"). The interest rate swaps fix 98% , 82% , and 77% of the principal value of the 2022 Term Loan from February 2017 through July 2018, July 2018 through June 2020, and June 2020 through January 2021, respectively. The fixed rate on the amounts hedged during these periods will be 4.25% , 4.25% and 4.75% , respectively. The total notional amount of these interest rate swaps in effect as of April 30, 2018 was $387.6 million . The total notional amount of these interest rate swaps in effect as of October 31, 2017 was $389.6 million . Ciena expects the variable rate payments to be received under the terms of the interest rate swaps to offset exactly the forecasted variable rate payments on the equivalent notional amounts of the term loans. These derivative contracts have been designated as cash flow hedges. Other information regarding Ciena's derivatives is immaterial for separate financial statement presentation. See Note 4 and Note 7 above.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	6 Months Ended
	Apr. 30, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income	ACCUMULATED OTHER COMPREHENSIVE INCOME The following table summarizes the changes in accumulated balances of other comprehensive income ("AOCI") for the six months ended April 30, 2018 : Unrealized Loss on Unrealized Gain (Loss) on Unrealized Gain on Forward Cumulative Foreign Currency Marketable Securities Foreign Currency Contracts Starting Interest Rate Swap Translation Adjustment Total Balance at October 31, 2017 $ (451 ) $ (1,386 ) $ 218 $ (9,398 ) $ (11,017 ) Other comprehensive income (loss) before reclassifications (337 ) (440 ) 4,725 1,069 5,017 Amounts reclassified from AOCI — 405 523 — 928 Balance at April 30, 2018 $ (788 ) $ (1,421 ) $ 5,466 $ (8,329 ) $ (5,072 ) The following table summarizes the changes in AOCI for the six months ended April 30, 2017 : Unrealized Gain/(Loss) on Unrealized Gain (Loss) on Unrealized Gain (Loss) on Forward Cumulative Foreign Currency Marketable Securities Foreign Currency Contracts Starting Interest Rate Swap Translation Adjustment Total Balance at October 31, 2016 $ 139 $ (1,091 ) $ (5,967 ) $ (17,410 ) $ (24,329 ) Other comprehensive income (loss) before reclassifications (527 ) 52 3,556 (1,753 ) 1,328 Amounts reclassified from AOCI — 474 1,341 — 1,815 Balance at April 30, 2017 $ (388 ) $ (565 ) $ (1,070 ) $ (19,163 ) $ (21,186 ) All amounts reclassified from AOCI related to settlement (gains) losses on foreign currency forward contracts designated as cash flow hedges impacted revenue or research and development expense on the Condensed Consolidated Statements of Operations. All amounts reclassified from AOCI related to settlement (gains) losses on forward starting interest rate swaps designated as cash flow hedges impacted interest and other income (loss), net on the Condensed Consolidated Statements of Operations.

Short-Term and Long-Term Debt

Short-Term and Long-Term Debt	6 Months Ended
	Apr. 30, 2018
Debt Disclosure [Abstract]
Short-Term and Long-Term Debt	SHORT-TERM AND LONG-TERM DEBT Outstanding Term Loan Payable 2022 Term Loan The net carrying value of Ciena's Term Loan due January 30, 2022 (the "2022 Term Loan") was comprised of the following for the fiscal periods indicated (in thousands): April 30, 2018 October 31, 2017 Term Loan Payable due January 30, 2022 $ 391,566 $ 392,972 Deferred debt issuance costs that were deducted from the carrying amounts of the 2022 Term Loan totaled $2.7 million at April 30, 2018 and $3.1 million at October 31, 2017 . Deferred debt issuance costs are amortized using the straight-line method, which approximates the effect of the effective interest rate method, through the maturity of the 2022 Term Loan. The amortization of deferred debt issuance costs for the 2022 Term Loan is included in interest expense, and was $0.4 million and $0.2 million during the first six months of fiscal 2018 and 2017 , respectively. The carrying values of the 2022 Term Loan listed above are also net of any unamortized debt discounts. The principal balance, unamortized debt discount, deferred debt issuance costs and net carrying value of the liability components of Ciena's 2022 Term Loan were as follows as of April 30, 2018 (in thousands): Principal Balance Unamortized Debt Discount Deferred Debt Issuance Costs Net Carrying Value Term Loan Payable due January 30, 2022 $ 396,000 $ (1,694 ) $ (2,740 ) $391,566 The following table sets forth the carrying value and the estimated fair value of Ciena's 2022 Term Loan (in thousands): April 30, 2018 Carrying Value Fair Value (1) Term Loan Payable due January 30, 2022 $ 391,566 $ 397,980 (1) Ciena's term loan is categorized as Level 2 in the fair value hierarchy. Ciena estimated the fair value of its 2022 Term Loan using a market approach based upon observable inputs, such as current market transactions involving comparable securities. Outstanding Convertible Notes Payable The net carrying values of Ciena's outstanding convertible notes payable was comprised of the following for the fiscal periods indicated (in thousands): April 30, 2018 October 31, 2017 3.75% Convertible Senior Notes due October 15, 2018 (Original) $ 61,180 $ 61,071 3.75% Convertible Senior Notes due October 15, 2018 (New) 288,028 287,221 4.0% Convertible Senior Notes due December 15, 2020 197,972 194,717 $ 547,180 $ 543,009 Deferred debt issuance costs that were deducted from the carrying amounts of the convertible notes payable totaled $1.3 million at April 30, 2018 and $2.1 million at October 31, 2017 . Deferred debt issuance costs are amortized using the straight-line method, which approximates the effect of the effective interest rate method, through the maturity of the convertible notes payable. The amortization of deferred debt issuance costs is included in interest expense, and was $0.8 million and $1.0 million during the first six months of fiscal 2018 and 2017 , respectively. The carrying values of the convertible notes payable listed above also include accretion of principal and are net of any unamortized debt discounts. The principal balance, unamortized debt discount, deferred debt issuance costs and net carrying value of the liability and equity components of Ciena's outstanding issues of convertible notes were as follows as of April 30, 2018 (in thousands): Liability Component Equity Component Principal Balance Unamortized Debt Discount Deferred Debt Issuance Costs Net Carrying Value Net Carrying Value 3.75% Convertible Senior Notes, due October 15, 2018 (Original) $ 61,270 $ — $ (90 ) $ 61,180 $ — 3.75% Convertible Senior Notes, due October 15, 2018 (New) $ 288,730 $ (277 ) $ (425 ) $ 288,028 $ — 4.0% Convertible Senior Notes due December 15, 2020 (1) $ 206,857 $ (8,079 ) $ (806 ) $ 197,972 $ 43,131 (1) Includes accretion of principal at a rate of 1.85% per year The following table sets forth, in thousands, the net carrying value and the estimated fair value of Ciena’s outstanding issues of convertible notes as of April 30, 2018 : April 30, 2018 Net Carrying Value Fair Value (1) 3.75% Convertible Senior Notes, due October 15, 2018 (Original) $ 61,180 $ 80,907 3.75% Convertible Senior Notes, due October 15, 2018 (New) 288,028 381,268 4.0% Convertible Senior Notes due December 15, 2020 197,972 265,125 $ 547,180 $ 727,300 (1) The convertible notes were categorized as Level 2 in the fair value hierarchy. Ciena estimates the fair value of its outstanding convertible notes using a market approach based on observable inputs, such as current market transactions involving comparable securities.

Earnings Per Share Calculation

Earnings Per Share Calculation	6 Months Ended
	Apr. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share Calculation	EARNINGS PER SHARE CALCULATION The following table (in thousands except per share amounts) is a reconciliation of the numerator and denominator of the basic net income (loss) per common share (“Basic EPS”) and the diluted net income (loss) per potential common share (“Diluted EPS”). Basic EPS is computed using the weighted average number of common shares outstanding. Diluted EPS is computed using the weighted average number of the following, in each case, to the extent the effect is not anti-dilutive: (i) common shares outstanding; (ii) shares issuable upon vesting of restricted stock units; (iii) shares issuable under Ciena’s employee stock purchase plan and upon exercise of outstanding stock options, using the treasury stock method; (iv) shares underlying Ciena’s outstanding convertible notes for which Ciena uses the treasury stock method (the New Notes); and (v) shares underlying Ciena’s outstanding convertible notes for which Ciena uses the if-converted method. Quarter Ended April 30, Six Months Ended April 30, Numerator 2018 2017 2018 2017 Net income (loss) $ 13,856 $ 38,026 $ (459,507 ) $ 41,887 Add: Interest expense associated with 0.875% Convertible Senior Notes due 2017 (1) — 495 — 1,097 Add: Interest expense associated with 3.75% Convertible Senior Notes due 2018 (Original) — 3,588 — — Net income (loss) used to calculate Diluted EPS $ 13,856 $ 42,109 $ (459,507 ) $ 42,984 Quarter Ended April 30, Six Months Ended April 30, Denominator 2018 2017 2018 2017 Basic weighted average shares outstanding 143,975 141,743 143,948 141,223 Add: Shares underlying outstanding stock options and restricted stock units and issuable under employee stock purchase plan 1,345 1,317 — 1,409 Add: Shares underlying 0.875% Convertible Senior Notes due 2017 (1) — 4,857 — 5,210 Add: Shares underlying 3.75% Convertible Senior Notes due 2018 (New) (2) 2,653 — — — Add: Shares underlying 3.75% Convertible Senior Notes due 2018 (Original) — 17,356 — — Dilutive weighted average shares outstanding 147,973 165,273 143,948 147,842 Quarter Ended April 30, Six Months Ended April 30, EPS 2018 2017 2018 2017 Basic EPS $ 0.10 $ 0.27 $ (3.19 ) $ 0.30 Diluted EPS $ 0.09 $ 0.25 $ (3.19 ) $ 0.29 The following table summarizes the weighted average shares excluded from the calculation of the denominator for Diluted EPS due to their anti-dilutive effect for the periods indicated (in thousands): Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Shares underlying stock options and restricted stock units 304 725 2,496 1,141 3.75% Convertible Senior Notes due October 15, 2018 (Original) 3,038 — 3,038 17,356 3.75% Convertible Senior Notes due October 15, 2018 (New) (2) — — 1,672 — 4.0% Convertible Senior Notes due December 15, 2020 9,198 9,198 9,198 9,198 Total shares excluded due to anti-dilutive effect 12,540 9,923 16,404 27,695 (1) Ciena's 0.875% convertible senior notes were paid at maturity during the third quarter of fiscal 2017. (2) Upon any conversion of the outstanding 3.75% Convertible Senior Notes due 2018 ("New Notes"), Ciena intends to settle the principal amount thereof in cash. Accordingly, Ciena uses the treasury stock method for calculating any potential dilutive effect of the conversion spread on diluted net income per share, if applicable. The 14.3 million shares underlying the New Notes will have a dilutive impact on diluted net income per share of common stock when the average market price of Ciena common stock for a given period exceeds the conversion price of $ 20.17 per share for the New Notes. During the second quarter of fiscal 2018 , the average market price of Ciena common stock was $ 24.76 . As a result, for the quarter ended April 30 , 2018 , the conversion spread for the New Notes is 2.7 million shares and included in the calculation of the denominator. For the six months ended April 30, 2018 , the conversion spread for the New Notes is 1.7 million shares; however, these shares were excluded from the calculation of the denominator as their inclusion would have had an anti-dilutive effect.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Apr. 30, 2018
Equity [Abstract]
Stockholders' Equity	STOCKHOLDERS' EQUITY Adoption of ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting In connection with the adoption of ASU 2016-09, 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. Ciena also elected to recognize forfeitures of stock awards when they occur, rather than 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 period of adoption. Stock Repurchase Program On December 7, 2017, Ciena announced that its Board of Directors authorized a program to repurchase up to $300 million of Ciena’s common stock through the end of fiscal 2020. Ciena may purchase shares at management’s discretion in the open market, in privately negotiated transactions, in transactions structured through investment banking institutions, or a combination of the foregoing. Ciena may also, from time to time, enter into Rule 10b5-1 plans to facilitate repurchases of its shares under this authorization. The amount and timing of repurchases are subject to a variety of factors, including liquidity, cash flow, stock price, and general business and market conditions. The program may be modified, suspended, or discontinued at any time. A summary of the stock repurchase program, reported based on trade date, is summarized as follows: Shares Repurchased Weighted-Average Price per Share Amount Repurchased (in thousands) Cumulative balance at October 31, 2017 — $ — $ — Repurchase of common stock under the stock repurchase program 1,627,233 24.06 39,147 Cumulative balance at April 30, 2018 1,627,233 $ 24.06 $ 39,147 The purchase price for the shares of Ciena's stock repurchased is reflected as a reduction to stockholders' equity. Ciena is required to allocate the purchase price of the repurchased shares as a reduction of common stock and additional paid-in capital.

Share-Based Compensation Expens

Share-Based Compensation Expense	6 Months Ended
	Apr. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation Expense	SHARE-BASED COMPENSATION EXPENSE The following table summarizes share-based compensation expense for the periods indicated (in thousands): Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Product costs $ 824 $ 708 $ 1,496 $ 1,269 Service costs 722 679 1,346 1,307 Share-based compensation expense included in cost of sales 1,546 1,387 2,842 2,576 Research and development 3,796 3,653 7,052 6,862 Sales and marketing 3,760 3,513 7,088 6,386 General and administrative 5,109 3,417 9,583 8,870 Share-based compensation expense included in operating expense 12,665 10,583 23,723 22,118 Share-based compensation expense capitalized in inventory, net (45 ) 35 (6 ) 136 Total share-based compensation $ 14,166 $ 12,005 $ 26,559 $ 24,830 As of April 30, 2018 , total unrecognized share-based compensation expense was approximately $93.0 million which relates to unvested restricted stock units and is expected to be recognized over a weighted-average period of 1.6 years.

Segments and Entity-Wide Disclo

Segments and Entity-Wide Disclosures	6 Months Ended
	Apr. 30, 2018
Segment Reporting [Abstract]
Segments and Entity-Wide Disclosures	SEGMENTS AND ENTITY-WIDE DISCLOSURES Segment Reporting Ciena manages its business, measures its performance and allocates its resources based on the following operating segments: • Networking Platforms reflects sales of Ciena’s Converged Packet Optical and Packet Networking product lines . ◦ Converged Packet Optical — includes the 6500 Packet-Optical Platform, the 5430 Reconfigurable Switching System, Waveserver stackable interconnect system, the family of CoreDirector® Multiservice Optical Switches and the OTN configuration for the 5410 Reconfigurable Switching System. This product line also includes sales of the Z-Series Packet-Optical Platform. As of the first quarter of fiscal 2018, sales of Optical Transport products are also reflected within the Converged Packet Optical product line for all periods presented. ◦ Packet Networking — includes the 3000 family of service delivery switches and service aggregation switches and the 5000 family of service aggregation switches. This product line also includes the 8700 Packetwave Platform and the Ethernet packet configuration for the 5410 Service Aggregation Switch. The Networking Platforms segment also includes sales of operating system software and enhanced software features embedded in each of the product lines above. Revenue from this segment is included in product revenue on the Condensed Consolidated Statements of Operations. • Software and Software-Related Services reflects sales of Ciena’s network virtualization, management, control and orchestration software solutions and software-related services, including subscription, installation, support, and consulting services. ◦ This segment includes Ciena’s Blue Planet network virtualization, service orchestration and network management software platform. Ciena's Blue Planet platform includes multi-domain service orchestration (MDSO), network function virtualization (NFV), management and orchestration (NFV MANO), and Ciena's manage, control and plan (MCP) domain controller solution, SDN Multilayer Controller and V-WAN application. ◦ This segment includes Ciena’s element and network management solutions and planning tools, including the OneControl Unified Management System, ON-Center® Network & Service Management Suite, Ethernet Services Manager, Optical Suite Release and Planet Operate. As Ciena seeks adoption of its Blue Planet software platform and transitions features, functionality and customers to this platform, Ciena expects revenue declines for its other element and network management solutions. Revenue from the software platforms portion of this segment is included in product revenue on the Condensed Consolidated Statements of Operations. Revenue from software-related services is included in services revenue on the Condensed Consolidated Statements of Operations. • Global Services reflects sales of a broad range of Ciena’s services for consulting and network design, installation and deployment, maintenance support and training activities. Revenue from this segment is included in services revenue on the Condensed Consolidated Statements of Operations. Ciena's long-lived assets, including equipment, building, furniture and fixtures, finite-lived intangible assets and maintenance spares, are not reviewed by Ciena's chief operating decision maker for purposes of evaluating performance and allocating resources. As of April 30, 2018 , equipment, building, furniture and fixtures, net totaled $298.6 million primarily supporting asset groups within Ciena's Networking Platforms and Software and Software-Related Services segments and supporting Ciena's unallocated selling and general and administrative activities. As of April 30, 2018 , $34.5 million of Ciena's intangible assets, net were assigned to asset groups within Ciena's Networking Platforms segment and $56.1 million of Ciena's intangible assets, net were assigned to asset groups within Ciena's Software and Software-Related Services segment. As of April 30, 2018 , all of the maintenance spares, net, totaling $43.2 million , were assigned to asset groups within Ciena's Global Services segment. Segment Revenue The table below (in thousands) sets forth Ciena’s segment revenue for the respective periods: Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Revenue: Networking Platforms Converged Packet Optical $ 527,867 $ 505,161 $ 955,297 $ 922,911 Packet Networking 63,815 66,326 132,418 138,520 Total Networking Platforms 591,682 571,487 1,087,715 1,061,431 Software and Software-Related Services Software Platforms 12,544 13,143 42,120 30,192 Software-Related Services 26,201 24,573 50,112 46,904 Total Software and Software-Related Services 38,745 37,716 92,232 77,096 Global Services Maintenance Support and Training 60,904 58,241 116,862 113,231 Installation and Deployment 28,209 28,695 58,225 56,614 Consulting and Network Design 10,438 10,883 21,079 20,147 Total Global Services 99,551 97,819 196,166 189,992 Consolidated revenue $ 729,978 $ 707,022 $ 1,376,113 $ 1,328,519 Segment Profit Segment profit is determined based on internal performance measures used by Ciena's chief executive officer to assess the performance of each operating segment in a given period. In connection with that assessment, the chief executive officer excludes the following items: selling and marketing costs; general and administrative costs; amortization of intangible assets; significant asset impairments and restructuring costs; interest and other income (loss), net; interest expense; and provision for income taxes. The table below (in thousands) sets forth Ciena’s segment profit and the reconciliation to consolidated net income (loss) during the respective periods indicated: Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Segment profit: Networking Platforms $ 126,823 $ 150,464 $ 215,392 $ 264,210 Software and Software-Related Services 8,276 4,551 31,911 12,252 Global Services 41,284 41,602 82,321 77,071 Total segment profit 176,383 196,617 329,624 353,533 Less: Non-performance operating expenses Selling and marketing 97,359 88,551 185,874 173,553 General and administrative 38,976 34,990 77,382 70,854 Amortization of intangible assets 3,623 10,980 7,246 25,531 Significant asset impairments and restructuring costs 4,359 4,276 10,320 6,671 Add: Other non-performance financial items Interest expense and other income (loss), net (11,735 ) (16,226 ) (23,894 ) (31,059 ) Less: Provision for income taxes 6,475 3,568 484,415 3,978 Consolidated net income (loss) $ 13,856 $ 38,026 $ (459,507 ) $ 41,887 Entity-Wide Reporting Ciena's revenue includes $392.8 million and $392.0 million of United States revenue for the second quarter of fiscal 2018 and 2017 , respectively. Ciena's revenue includes $79.4 million of India revenue for the second quarter of fiscal 2018 . For the six months ended April 30, 2018 and 2017 , United States revenue was $776.1 million and $771.7 million , respectively. No other country accounted for 10% or more of total revenue for the periods presented above. The following table reflects Ciena's geographic distribution of equipment, building, furniture and fixtures, net, with any country accounting for at least 10% of total equipment, building, furniture and fixtures, net, specifically identified. Equipment, building, furniture and fixtures, net, attributable to geographic regions outside of the U.S. and Canada are reflected as “Other International.” For the periods below, Ciena's geographic distribution of equipment, building, furniture and fixtures was as follows (in thousands): April 30, October 31, Canada $ 197,632 $ 203,491 United States 81,051 90,482 Other International 19,948 14,492 Total $ 298,631 $ 308,465 For the periods below, AT&T was the only customer that accounted for at least 10% of Ciena’s revenue as follows (in thousands): Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 AT&T $ 85,419 $ 107,532 $ 176,065 $ 203,969 AT&T purchased products and services from each of Ciena's operating segments.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Apr. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Canadian Grant During the second quarter of fiscal 2018, Ciena entered into agreements related to the Evolution of Networking Services through a Corridor in Quebec and Ontario for Research and Innovation ("ENCQOR") project with the Canadian federal government, the government of the province of Ontario and the government of the province of Quebec to develop a 5G technology corridor between Quebec and Ontario to promote research and development, small business enterprises and entrepreneurs in Canada. Under these agreements, Ciena can receive up to an aggregate CAD$ 57.6 million (approximately $45.0 million ) in reimbursement by the three Canadian government entities for eligible costs over a period commencing on February 20, 2017 and ending on March 31, 2022. Ciena anticipates receiving recurring disbursements over this period. Amounts received under the agreements are subject to recoupment in the event that Ciena fails to achieve certain minimum investment, employment and project milestones. During the second quarter of fiscal 2018, Ciena recorded a CAD $10.3 million (approximately $8.1 million ) benefit as a reduction in research and development expense, related to eligible costs that it incurred from the commencement date of February 20, 2017 to April 30, 2018, because it believes it has complied with the conditions of the agreements entitling it to this amount. In future periods, through the term of these agreements, Ciena expects to record a quarterly benefit to operating expense of approximately CAD$ 2.95 million (approximately $2.3 million ) related to these grants. Foreign Tax Contingencies Ciena is subject to various tax liabilities arising in the ordinary course of business. Ciena does not expect that the ultimate settlement of these tax liabilities will have a material effect on its results of operations, financial position or cash flows. Litigation As a result of the acquisition of Cyan in August 2015, Ciena became a defendant in a securities class action lawsuit. On April 1, 2014, a purported stockholder class action lawsuit was filed in the Superior Court of California, County of San Francisco, against Cyan, the members of Cyan’s board of directors, Cyan’s former Chief Financial Officer, and the underwriters of Cyan’s initial public offering. On April 30, 2014, a substantially similar lawsuit was filed in the same court against the same defendants. The two cases were consolidated as Beaver County Employees Retirement Fund, et al. v. Cyan, Inc. et al., Case No. CGC-14-538355. The consolidated complaint alleges violations of federal securities laws on behalf of a purported class consisting of purchasers of Cyan’s common stock pursuant or traceable to the registration statement and prospectus for Cyan’s initial public offering in April 2013, and seeks unspecified compensatory damages and other relief. On May 19, 2015, the proposed class was certified. On August 25, 2015, the defendants filed a motion for judgment on the pleadings based on an alleged lack of subject matter jurisdiction over the case, which motion was denied on October 23, 2015. On May 24, 2016, the defendants filed a petition for a writ of certiorari on the jurisdiction issue with the U.S. Supreme Court, which petition was granted on June 27, 2017. The matter was stayed by the Superior Court pending the outcome of the Supreme Court’s decision. On March 20, 2018, the Supreme Court held that the Superior Court had subject matter jurisdiction over the case. A case management conference is scheduled before the Superior Court during the third quarter of fiscal 2018. Ciena believes that the consolidated lawsuit is without merit and intends to defend it vigorously. Internal Investigations During fiscal 2017, one of Ciena’s third-party vendors raised allegations about certain questionable payments to one or more individuals employed by a customer in a country in the ASEAN region. Ciena promptly initiated an internal investigation into the matter, with the assistance of outside counsel, which investigation corroborated direct and indirect payments to one such individual and sought to determine whether the payments may have violated applicable laws and regulations, including the U.S. Foreign Corrupt Practices Act (“FCPA”). In September 2017, Ciena voluntarily contacted the SEC and the U.S. Department of Justice (“DOJ”) to advise them of the relevant events and the findings of Ciena’s internal investigation. With the direct oversight of Ciena's Board of Directors, Ciena continues to cooperate fully with the SEC and DOJ in their review of the investigation. Ciena’s operations in the relevant country have constituted less than 1.5% of consolidated revenues as reported by Ciena in each fiscal year since 2012. Ciena does not currently anticipate that this matter will have a material adverse effect on its business, financial condition or results of operations. However, as discussions with the SEC and DOJ are ongoing, the ultimate outcome of this matter cannot be predicted at this time. As of the filing of this Report, no provision with respect to this matter has been made in Ciena’s consolidated financial statements. Any determination that Ciena’s operations or activities are not in compliance with the FCPA or other applicable laws or regulations could result in the imposition of fines, civil and criminal penalties, and equitable remedies, including disgorgement or injunctive relief. In addition to the matters described in “Litigation” and “Internal Investigations” above, Ciena is subject to various legal proceedings, claims and other matters arising in the ordinary course of business, including those that relate to employment, commercial, tax and other regulatory matters. Ciena is also subject to intellectual property related claims, including claims against third parties that may involve contractual indemnification obligations on the part of Ciena. Ciena does not expect that the ultimate costs to resolve such matters will have a material effect on its results of operations, financial position or cash flows.

Subsequent Events

Subsequent Events	6 Months Ended
	Apr. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS Stock Repurchase Program From the end of the second quarter of fiscal 2018 through June 4, 2018, Ciena repurchased an additional 611,942 shares of its common stock, for an aggregate purchase price of $15.4 million at an average price of $25.15 per share, inclusive of repurchases pending settlement. As of June 4, 2018 , Ciena has an aggregate of $245.5 million of authorized funds remaining under its Stock Repurchase Program. Packet Design Acquisition On May 30, 2018, Ciena entered into a definitive agreement to acquire privately-held Packet Design, LLC, a provider of network performance management software focused on Layer 3 network optimization, topology and route analytics. The transaction is expected to close during Ciena’s fiscal third quarter 2018 and is subject to customary closing conditions.

Significant Accounting Polici26

Significant Accounting Policies (Policies)	6 Months Ended
	Apr. 30, 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 complied with the conditions attached to the grant and that grant proceeds will be received. Grant benefits are recorded to the line item in 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. Ciena expects that the adoption of ASU 2014-09 will require that it 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.

Restructuring Costs (Tables)

Restructuring Costs (Tables)	6 Months Ended
	Apr. 30, 2018
Restructuring and Related Activities [Abstract]
Schedule of Activity and Balance of the Restructuring Liability Accounts	The following table sets forth the restructuring activity and balance of the restructuring liability accounts for the six months ended April 30, 2018 (in thousands): Workforce reduction Consolidation of excess facilities Total Balance at October 31, 2017 $ 1,291 $ 1,648 $ 2,939 Additional liability recorded 8,232 (1) 2,088 (2) 10,320 Cash payments (8,211 ) (1,896 ) (10,107 ) Balance at April 30, 2018 $ 1,312 $ 1,840 $ 3,152 Current restructuring liabilities $ 1,312 $ 865 $ 2,177 Non-current restructuring liabilities $ — $ 975 $ 975 (1) Reflects a global workforce reduction of approximately 150 employees during fiscal 2018 as part of a business optimization strategy to improve gross margin, constrain operating expense and redesign certain business processes. (2) Reflects unfavorable lease commitments in connection with a portion of facilities located in Petaluma, California. The following table sets forth the restructuring activity and balance of the restructuring liability accounts for the six months ended April 30, 2017 (in thousands): Workforce reduction Consolidation of excess facilities Total Balance at October 31, 2016 $ 868 $ 1,970 $ 2,838 Additional liability recorded 2,369 (1) 4,302 (2) 6,671 Cash payments (3,084 ) (1,133 ) (4,217 ) Balance at April 30, 2017 $ 153 $ 5,139 $ 5,292 Current restructuring liabilities $ 153 $ 4,928 $ 5,081 Non-current restructuring liabilities $ — $ 211 $ 211 (1) Reflects a global workforce reduction of approximately 50 employees during the first quarter of fiscal 2017 as part of a business optimization strategy to improve gross margin, constrain operating expense and redesign certain business processes and systems. (2) Reflects unfavorable lease commitments and relocation costs incurred during the second quarter of fiscal 2017 in connection with the facility transition from Ciena's existing research and development center located at Lab 10 on the former Nortel Carling Campus to a new campus facility in Ottawa, Canada.

Interest and Other Income (Lo28

Interest and Other Income (Loss), Net (Tables)	6 Months Ended
	Apr. 30, 2018
Other Income and Expenses [Abstract]
Schedule of Interest and Other Income (Loss), Net	The components of interest and other income (loss), net, are as follows (in thousands): Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Interest income $ 3,212 $ 1,507 $ 5,656 $ 2,789 Gains (losses) on non-hedge designated foreign currency forward contracts 2,868 (2,749 ) 2,169 (1,725 ) Foreign currency exchange gain (loss) (4,804 ) 1,292 (4,791 ) (1,125 ) Modification of term loan — (2,924 ) — (2,924 ) Other 20 (44 ) (163 ) 437 Interest and other income (loss), net $ 1,296 $ (2,918 ) $ 2,871 $ (2,548 )

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Apr. 30, 2018
Income Tax Disclosure [Abstract]
Schedule of Significant Components of Deferred Tax Assets and Liabilities	The significant components of DTA are as follows (in thousands): April 30, October 31, 2018 2017 Deferred tax assets: Reserves and accrued liabilities $ 36,115 $ 56,597 Depreciation and amortization 288,145 451,385 NOL and credit carry forward 538,869 803,622 Other 18,706 29,398 Gross deferred tax assets 881,835 1,341,002 Valuation allowance (147,011 ) (185,898 ) Deferred tax asset, net of valuation allowance $ 734,824 $ 1,155,104

Short-Term and Long-Term Inve30

Short-Term and Long-Term Investments (Tables)	6 Months Ended
	Apr. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Schedule of Short-Term and Long-Term Investments	As of the dates indicated, investments are comprised of the following (in thousands): April 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. government obligations: Included in short-term investments $ 239,291 $ — (601 ) $ 238,690 Included in long-term investments 59,066 — (171 ) 58,895 $ 298,357 $ — $ (772 ) $ 297,585 Commercial paper: Included in short-term investments $ 29,892 2 — $ 29,894 $ 29,892 $ 2 $ — $ 29,894 October 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. government obligations: Included in short-term investments $ 249,498 $ — $ (305 ) $ 249,193 Included in long-term investments 49,910 — (127 ) 49,783 $ 299,408 $ — $ (432 ) $ 298,976 Commercial paper: Included in short-term investments $ 29,939 1 — $ 29,940 $ 29,939 $ 1 $ — $ 29,940
Schedule of Legal Maturities of Debt Investments	The following table summarizes the final legal maturities of debt investments at April 30, 2018 (in thousands): Amortized Cost Estimated Fair Value Less than one year $ 269,183 $ 268,584 Due in 1-2 years 59,066 58,895 $ 328,249 $ 327,479

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Apr. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of the Fair Value of Assets and Liabilities Recorded on a Recurring Basis	As of the date indicated, the following table summarizes the assets and liabilities that are recorded at fair value on a recurring basis (in thousands): April 30, 2018 Level 1 Level 2 Total Assets: Money market funds $ 476,187 $ — $ 476,187 U.S. government obligations — 297,585 297,585 Commercial paper — 99,745 99,745 Foreign currency forward contracts — 97 97 Forward starting interest rate swaps — 6,333 6,333 Total assets measured at fair value $ 476,187 $ 403,760 $ 879,947 Liabilities: Foreign currency forward contracts $ — $ 1,317 $ 1,317 Total liabilities measured at fair value $ — $ 1,317 $ 1,317 October 31, 2017 Level 1 Level 2 Total Assets: Money market funds $ 511,355 $ — $ 511,355 U.S. government obligations — 298,976 298,976 Commercial paper — 89,865 89,865 Foreign currency forward contracts — 227 227 Forward starting interest rate swaps — 218 218 Total assets measured at fair value $ 511,355 $ 389,286 $ 900,641 Liabilities: Foreign currency forward contracts $ — $ 2,129 $ 2,129 Total liabilities measured at fair value $ — $ 2,129 $ 2,129
Schedule of Assets and Liabilities as Presented on Ciena's Condensed Consolidated Balance Sheets	As of the date indicated, the assets and liabilities above are presented on Ciena’s Condensed Consolidated Balance Sheet as follows (in thousands): April 30, 2018 Level 1 Level 2 Total Assets: Cash equivalents $ 476,187 $ 69,851 $ 546,038 Short-term investments — 268,584 268,584 Prepaid expenses and other — 97 97 Long-term investments — 58,895 58,895 Other long-term assets — 6,333 6,333 Total assets measured at fair value $ 476,187 $ 403,760 $ 879,947 Liabilities: Accrued liabilities $ — $ 1,317 $ 1,317 Total liabilities measured at fair value $ — $ 1,317 $ 1,317 October 31, 2017 Level 1 Level 2 Total Assets: Cash equivalents $ 511,355 $ 59,925 $ 571,280 Short-term investments — 279,133 279,133 Prepaid expenses and other — 227 227 Long-term investments — 49,783 49,783 Other long-term assets — 218 218 Total assets measured at fair value $ 511,355 $ 389,286 $ 900,641 Liabilities: Accrued liabilities $ — $ 2,129 $ 2,129 Total liabilities measured at fair value $ — $ 2,129 $ 2,129

Inventories (Tables)

Inventories (Tables)	6 Months Ended
	Apr. 30, 2018
Inventory Disclosure [Abstract]
Schedule of Inventories	As of the dates indicated, inventories are comprised of the following (in thousands): April 30, October 31, Raw materials $ 48,356 $ 52,898 Work-in-process 13,253 18,623 Finished goods 165,733 185,488 Deferred cost of goods sold 55,161 61,340 282,503 318,349 Provision for excess and obsolescence (51,165 ) (51,206 ) $ 231,338 $ 267,143

Accrued Liabilities and Other33

Accrued Liabilities and Other Short-Term Obligations (Tables)	6 Months Ended
	Apr. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Schedule of Accrued Liabilities	As of the dates indicated, accrued liabilities and other short-term obligations are comprised of the following (in thousands): April 30, October 31, Compensation, payroll related tax and benefits (1) $ 78,744 $ 113,272 Warranty 43,392 42,456 Vacation 42,744 39,778 Capital lease obligations 3,828 3,772 Interest payable 3,602 3,612 Other 97,921 120,044 $ 270,231 $ 322,934 (1) Reduction is primarily due to the timing of bonus payments to employees under Ciena's annual cash incentive compensation plan.
Schedule of Accrued Warranties	The following table summarizes the activity in Ciena’s accrued warranty for the fiscal periods indicated (in thousands): Six Months Ended April 30, Beginning Balance Current Period Provisions (1) Settlements Ending Balance 2017 $ 52,324 2,347 (8,646 ) $ 46,025 2018 $ 42,456 10,565 (9,629 ) $ 43,392 (1) As a result of lower than expected actual failure rates, Ciena adjusted its fiscal 2017 provision for warranty. This adjustment had the effect of reducing warranty provision by $6.3 million for the six months ended April 30, 2017 .

Accumulated Other Comprehensi34

Accumulated Other Comprehensive Income (Tables)	6 Months Ended
	Apr. 30, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income	The following table summarizes the changes in accumulated balances of other comprehensive income ("AOCI") for the six months ended April 30, 2018 : Unrealized Loss on Unrealized Gain (Loss) on Unrealized Gain on Forward Cumulative Foreign Currency Marketable Securities Foreign Currency Contracts Starting Interest Rate Swap Translation Adjustment Total Balance at October 31, 2017 $ (451 ) $ (1,386 ) $ 218 $ (9,398 ) $ (11,017 ) Other comprehensive income (loss) before reclassifications (337 ) (440 ) 4,725 1,069 5,017 Amounts reclassified from AOCI — 405 523 — 928 Balance at April 30, 2018 $ (788 ) $ (1,421 ) $ 5,466 $ (8,329 ) $ (5,072 ) The following table summarizes the changes in AOCI for the six months ended April 30, 2017 : Unrealized Gain/(Loss) on Unrealized Gain (Loss) on Unrealized Gain (Loss) on Forward Cumulative Foreign Currency Marketable Securities Foreign Currency Contracts Starting Interest Rate Swap Translation Adjustment Total Balance at October 31, 2016 $ 139 $ (1,091 ) $ (5,967 ) $ (17,410 ) $ (24,329 ) Other comprehensive income (loss) before reclassifications (527 ) 52 3,556 (1,753 ) 1,328 Amounts reclassified from AOCI — 474 1,341 — 1,815 Balance at April 30, 2017 $ (388 ) $ (565 ) $ (1,070 ) $ (19,163 ) $ (21,186 )

Short-Term and Long-Term Debt (

Short-Term and Long-Term Debt (Tables)	6 Months Ended
	Apr. 30, 2018
Debt Disclosure [Abstract]
Schedule of Carrying Values and Estimated Fair Values of Convertible Notes	The following table sets forth, in thousands, the net carrying value and the estimated fair value of Ciena’s outstanding issues of convertible notes as of April 30, 2018 : April 30, 2018 Net Carrying Value Fair Value (1) 3.75% Convertible Senior Notes, due October 15, 2018 (Original) $ 61,180 $ 80,907 3.75% Convertible Senior Notes, due October 15, 2018 (New) 288,028 381,268 4.0% Convertible Senior Notes due December 15, 2020 197,972 265,125 $ 547,180 $ 727,300 (1) The convertible notes were categorized as Level 2 in the fair value hierarchy. Ciena estimates the fair value of its outstanding convertible notes using a market approach based on observable inputs, such as current market transactions involving comparable securities. The net carrying value of Ciena's Term Loan due January 30, 2022 (the "2022 Term Loan") was comprised of the following for the fiscal periods indicated (in thousands): April 30, 2018 October 31, 2017 Term Loan Payable due January 30, 2022 $ 391,566 $ 392,972 The following table sets forth the carrying value and the estimated fair value of Ciena's 2022 Term Loan (in thousands): April 30, 2018 Carrying Value Fair Value (1) Term Loan Payable due January 30, 2022 $ 391,566 $ 397,980 (1) Ciena's term loan is categorized as Level 2 in the fair value hierarchy. Ciena estimated the fair value of its 2022 Term Loan using a market approach based upon observable inputs, such as current market transactions involving comparable securities. The net carrying values of Ciena's outstanding convertible notes payable was comprised of the following for the fiscal periods indicated (in thousands): April 30, 2018 October 31, 2017 3.75% Convertible Senior Notes due October 15, 2018 (Original) $ 61,180 $ 61,071 3.75% Convertible Senior Notes due October 15, 2018 (New) 288,028 287,221 4.0% Convertible Senior Notes due December 15, 2020 197,972 194,717 $ 547,180 $ 543,009
Schedule of Debt Details	The principal balance, unamortized debt discount, deferred debt issuance costs and net carrying value of the liability components of Ciena's 2022 Term Loan were as follows as of April 30, 2018 (in thousands): Principal Balance Unamortized Debt Discount Deferred Debt Issuance Costs Net Carrying Value Term Loan Payable due January 30, 2022 $ 396,000 $ (1,694 ) $ (2,740 ) $391,566 The principal balance, unamortized debt discount, deferred debt issuance costs and net carrying value of the liability and equity components of Ciena's outstanding issues of convertible notes were as follows as of April 30, 2018 (in thousands): Liability Component Equity Component Principal Balance Unamortized Debt Discount Deferred Debt Issuance Costs Net Carrying Value Net Carrying Value 3.75% Convertible Senior Notes, due October 15, 2018 (Original) $ 61,270 $ — $ (90 ) $ 61,180 $ — 3.75% Convertible Senior Notes, due October 15, 2018 (New) $ 288,730 $ (277 ) $ (425 ) $ 288,028 $ — 4.0% Convertible Senior Notes due December 15, 2020 (1) $ 206,857 $ (8,079 ) $ (806 ) $ 197,972 $ 43,131 (1) Includes accretion of principal at a rate of 1.85% per year

Earnings Per Share Calculation

Earnings Per Share Calculation (Tables)	6 Months Ended
	Apr. 30, 2018
Earnings Per Share [Abstract]
Schedule of Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share	The following table (in thousands except per share amounts) is a reconciliation of the numerator and denominator of the basic net income (loss) per common share (“Basic EPS”) and the diluted net income (loss) per potential common share (“Diluted EPS”). Basic EPS is computed using the weighted average number of common shares outstanding. Diluted EPS is computed using the weighted average number of the following, in each case, to the extent the effect is not anti-dilutive: (i) common shares outstanding; (ii) shares issuable upon vesting of restricted stock units; (iii) shares issuable under Ciena’s employee stock purchase plan and upon exercise of outstanding stock options, using the treasury stock method; (iv) shares underlying Ciena’s outstanding convertible notes for which Ciena uses the treasury stock method (the New Notes); and (v) shares underlying Ciena’s outstanding convertible notes for which Ciena uses the if-converted method. Quarter Ended April 30, Six Months Ended April 30, Numerator 2018 2017 2018 2017 Net income (loss) $ 13,856 $ 38,026 $ (459,507 ) $ 41,887 Add: Interest expense associated with 0.875% Convertible Senior Notes due 2017 (1) — 495 — 1,097 Add: Interest expense associated with 3.75% Convertible Senior Notes due 2018 (Original) — 3,588 — — Net income (loss) used to calculate Diluted EPS $ 13,856 $ 42,109 $ (459,507 ) $ 42,984 Quarter Ended April 30, Six Months Ended April 30, Denominator 2018 2017 2018 2017 Basic weighted average shares outstanding 143,975 141,743 143,948 141,223 Add: Shares underlying outstanding stock options and restricted stock units and issuable under employee stock purchase plan 1,345 1,317 — 1,409 Add: Shares underlying 0.875% Convertible Senior Notes due 2017 (1) — 4,857 — 5,210 Add: Shares underlying 3.75% Convertible Senior Notes due 2018 (New) (2) 2,653 — — — Add: Shares underlying 3.75% Convertible Senior Notes due 2018 (Original) — 17,356 — — Dilutive weighted average shares outstanding 147,973 165,273 143,948 147,842 Quarter Ended April 30, Six Months Ended April 30, EPS 2018 2017 2018 2017 Basic EPS $ 0.10 $ 0.27 $ (3.19 ) $ 0.30 Diluted EPS $ 0.09 $ 0.25 $ (3.19 ) $ 0.29
Schedule of Weighted Average Shares Excluded From Calculation of Denominator for Basic and Diluted EPS	The following table summarizes the weighted average shares excluded from the calculation of the denominator for Diluted EPS due to their anti-dilutive effect for the periods indicated (in thousands): Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Shares underlying stock options and restricted stock units 304 725 2,496 1,141 3.75% Convertible Senior Notes due October 15, 2018 (Original) 3,038 — 3,038 17,356 3.75% Convertible Senior Notes due October 15, 2018 (New) (2) — — 1,672 — 4.0% Convertible Senior Notes due December 15, 2020 9,198 9,198 9,198 9,198 Total shares excluded due to anti-dilutive effect 12,540 9,923 16,404 27,695 (1) Ciena's 0.875% convertible senior notes were paid at maturity during the third quarter of fiscal 2017. (2) Upon any conversion of the outstanding 3.75% Convertible Senior Notes due 2018 ("New Notes"), Ciena intends to settle the principal amount thereof in cash. Accordingly, Ciena uses the treasury stock method for calculating any potential dilutive effect of the conversion spread on diluted net income per share, if applicable. The 14.3 million shares underlying the New Notes will have a dilutive impact on diluted net income per share of common stock when the average market price of Ciena common stock for a given period exceeds the conversion price of $ 20.17 per share for the New Notes. During the second quarter of fiscal 2018 , the average market price of Ciena common stock was $ 24.76 . As a result, for the quarter ended April 30 , 2018 , the conversion spread for the New Notes is 2.7 million shares and included in the calculation of the denominator. For the six months ended April 30, 2018 , the conversion spread for the New Notes is 1.7 million shares; however, these shares were excluded from the calculation of the denominator as their inclusion would have had an anti-dilutive effect.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Apr. 30, 2018
Equity [Abstract]
Schedule of Stock Repurchase Program	A summary of the stock repurchase program, reported based on trade date, is summarized as follows: Shares Repurchased Weighted-Average Price per Share Amount Repurchased (in thousands) Cumulative balance at October 31, 2017 — $ — $ — Repurchase of common stock under the stock repurchase program 1,627,233 24.06 39,147 Cumulative balance at April 30, 2018 1,627,233 $ 24.06 $ 39,147

Share-Based Compensation Expe38

Share-Based Compensation Expense (Tables)	6 Months Ended
	Apr. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-Based Compensation Expense	The following table summarizes share-based compensation expense for the periods indicated (in thousands): Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Product costs $ 824 $ 708 $ 1,496 $ 1,269 Service costs 722 679 1,346 1,307 Share-based compensation expense included in cost of sales 1,546 1,387 2,842 2,576 Research and development 3,796 3,653 7,052 6,862 Sales and marketing 3,760 3,513 7,088 6,386 General and administrative 5,109 3,417 9,583 8,870 Share-based compensation expense included in operating expense 12,665 10,583 23,723 22,118 Share-based compensation expense capitalized in inventory, net (45 ) 35 (6 ) 136 Total share-based compensation $ 14,166 $ 12,005 $ 26,559 $ 24,830

Segments and Entity-Wide Disc39

Segments and Entity-Wide Disclosures (Tables)	6 Months Ended
	Apr. 30, 2018
Segment Reporting [Abstract]
Schedule of Segment Revenue	The table below (in thousands) sets forth Ciena’s segment revenue for the respective periods: Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Revenue: Networking Platforms Converged Packet Optical $ 527,867 $ 505,161 $ 955,297 $ 922,911 Packet Networking 63,815 66,326 132,418 138,520 Total Networking Platforms 591,682 571,487 1,087,715 1,061,431 Software and Software-Related Services Software Platforms 12,544 13,143 42,120 30,192 Software-Related Services 26,201 24,573 50,112 46,904 Total Software and Software-Related Services 38,745 37,716 92,232 77,096 Global Services Maintenance Support and Training 60,904 58,241 116,862 113,231 Installation and Deployment 28,209 28,695 58,225 56,614 Consulting and Network Design 10,438 10,883 21,079 20,147 Total Global Services 99,551 97,819 196,166 189,992 Consolidated revenue $ 729,978 $ 707,022 $ 1,376,113 $ 1,328,519
Schedule of Segment Profit (Loss) and the Reconciliation to Consolidated Net Income (Loss)	The table below (in thousands) sets forth Ciena’s segment profit and the reconciliation to consolidated net income (loss) during the respective periods indicated: Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 Segment profit: Networking Platforms $ 126,823 $ 150,464 $ 215,392 $ 264,210 Software and Software-Related Services 8,276 4,551 31,911 12,252 Global Services 41,284 41,602 82,321 77,071 Total segment profit 176,383 196,617 329,624 353,533 Less: Non-performance operating expenses Selling and marketing 97,359 88,551 185,874 173,553 General and administrative 38,976 34,990 77,382 70,854 Amortization of intangible assets 3,623 10,980 7,246 25,531 Significant asset impairments and restructuring costs 4,359 4,276 10,320 6,671 Add: Other non-performance financial items Interest expense and other income (loss), net (11,735 ) (16,226 ) (23,894 ) (31,059 ) Less: Provision for income taxes 6,475 3,568 484,415 3,978 Consolidated net income (loss) $ 13,856 $ 38,026 $ (459,507 ) $ 41,887
Schedule of Ciena's Geographic Distribution of Revenue and Long-Lived Assets	For the periods below, Ciena's geographic distribution of equipment, building, furniture and fixtures was as follows (in thousands): April 30, October 31, Canada $ 197,632 $ 203,491 United States 81,051 90,482 Other International 19,948 14,492 Total $ 298,631 $ 308,465
Schedule of Revenue by Major Customers by Reporting Segments	For the periods below, AT&T was the only customer that accounted for at least 10% of Ciena’s revenue as follows (in thousands): Quarter Ended April 30, Six Months Ended April 30, 2018 2017 2018 2017 AT&T $ 85,419 $ 107,532 $ 176,065 $ 203,969

Significant Accounting Polici40

Significant Accounting Policies (Details) $ in Thousands	Oct. 31, 2017USD ($)
Significant Accounting Policies [Line Items]
Cumulative adjustment	$ 62,123
Retained earnings
Significant Accounting Policies [Line Items]
Cumulative adjustment	61,291
Retained earnings | ASU 2016-09, Excess tax benefit component
Significant Accounting Policies [Line Items]
Cumulative adjustment	62,100
Retained earnings | ASU 2016-09, Forfeiture rate component
Significant Accounting Policies [Line Items]
Cumulative adjustment	$ 800

Restructuring Costs (Details)

Restructuring Costs (Details) $ in Thousands	6 Months Ended
	Apr. 30, 2018USD ($)employee	Apr. 30, 2017USD ($)employee
Activity and balance of the restructuring liability accounts
Balance at beginning of period	$ 2,939	$ 2,838
Additional liability recorded	10,320	6,671
Cash payments	(10,107)	(4,217)
Balance at end of period	3,152	5,292
Current restructuring liabilities	2,177	5,081
Non-current restructuring liabilities	$ 975	$ 211
Workforce reduction
Restructuring Cost and Reserve [Line Items]
Number of employee reduction | employee	150	50
Activity and balance of the restructuring liability accounts
Balance at beginning of period	$ 1,291	$ 868
Additional liability recorded	8,232	2,369
Cash payments	(8,211)	(3,084)
Balance at end of period	1,312	153
Current restructuring liabilities	1,312	153
Non-current restructuring liabilities	0	0
Consolidation of excess facilities
Activity and balance of the restructuring liability accounts
Balance at beginning of period	1,648	1,970
Additional liability recorded	2,088	4,302
Cash payments	(1,896)	(1,133)
Balance at end of period	1,840	5,139
Current restructuring liabilities	865	4,928
Non-current restructuring liabilities	$ 975	$ 211

Interest and Other Income (Lo42

Interest and Other Income (Loss), Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Other Income and Expenses [Abstract]
Interest income	$ 3,212	$ 1,507	$ 5,656	$ 2,789
Gains (losses) on non-hedge designated foreign currency forward contracts	2,868	(2,749)	2,169	(1,725)
Foreign currency exchange gain (loss)	(4,804)	1,292	(4,791)	(1,125)
Modification of term loan	0	(2,924)	0	(2,924)
Other	20	(44)	(163)	437
Interest and other income (loss), net	$ 1,296	$ (2,918)	$ 2,871	$ (2,548)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Apr. 30, 2018	Oct. 31, 2018	Oct. 31, 2017
Income Tax Contingency [Line Items]
Provisional tax expense	$ 484,400
Remeasurement of net DTA	431,300
U.S. transition tax	45,600
Unrecognized deferred income tax liability	24,000
Cumulative adjustment			$ 62,123
Deferred tax asset, net	734,824		1,155,104
Valuation allowance	$ 147,011		185,898
Scenario, Forecast
Income Tax Contingency [Line Items]
Blended federal tax rate		23.40%
Retained earnings
Income Tax Contingency [Line Items]
Cumulative adjustment			61,291
ASU 2016-09, Excess tax benefit component
Income Tax Contingency [Line Items]
Deferred tax asset, net			62,100
ASU 2016-09, Excess tax benefit component | Retained earnings
Income Tax Contingency [Line Items]
Cumulative adjustment			$ 62,100

Income Taxes - Significant Comp

Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Deferred tax assets:
Reserves and accrued liabilities	$ 36,115	$ 56,597
Depreciation and amortization	288,145	451,385
NOL and credit carry forward	538,869	803,622
Other	18,706	29,398
Gross deferred tax assets	881,835	1,341,002
Valuation allowance	(147,011)	(185,898)
Deferred tax asset, net of valuation allowance	$ 734,824	$ 1,155,104

Short-Term and Long-Term Inve45

Short-Term and Long-Term Investments (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 328,249
Estimated Fair Value	327,479
U.S. government obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	298,357	$ 299,408
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(772)	(432)
Estimated Fair Value	297,585	298,976
U.S. government obligations | Included in short-term investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	239,291	249,498
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(601)	(305)
Estimated Fair Value	238,690	249,193
U.S. government obligations | Included in long-term investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	59,066	49,910
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(171)	(127)
Estimated Fair Value	58,895	49,783
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	29,892	29,939
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	0
Estimated Fair Value	29,894	29,940
Commercial paper | Included in short-term investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	29,892	29,939
Gross Unrealized Gains	2	1
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 29,894	$ 29,940

Short-Term and Long-Term Inve46

Short-Term and Long-Term Investments - Legal Maturities of Debt Investments (Details) $ in Thousands	Apr. 30, 2018USD ($)
Amortized Cost
Less than one year	$ 269,183
Due in 1-2 years	59,066
Amortized Cost	328,249
Estimated Fair Value
Less than one year	268,584
Due in 1-2 years	58,895
Estimated Fair Value	$ 327,479

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Assets:
U.S. government obligations	$ 327,479
Fair value, Measurements, Recurring
Assets:
Money market funds	476,187	$ 511,355
U.S. government obligations	297,585	298,976
Commercial paper	99,745	89,865
Foreign currency forward contracts	97	227
Forward starting interest rate swaps	6,333	218
Total assets measured at fair value	879,947	900,641
Liabilities:
Foreign currency forward contracts	1,317	2,129
Total liabilities measured at fair value	1,317	2,129
Fair value, Measurements, Recurring | Level 1
Assets:
Money market funds	476,187	511,355
U.S. government obligations	0	0
Commercial paper	0	0
Foreign currency forward contracts	0	0
Forward starting interest rate swaps	0	0
Total assets measured at fair value	476,187	511,355
Liabilities:
Foreign currency forward contracts	0	0
Total liabilities measured at fair value	0	0
Fair value, Measurements, Recurring | Level 2
Assets:
Money market funds	0	0
U.S. government obligations	297,585	298,976
Commercial paper	99,745	89,865
Foreign currency forward contracts	97	227
Forward starting interest rate swaps	6,333	218
Total assets measured at fair value	403,760	389,286
Liabilities:
Foreign currency forward contracts	1,317	2,129
Total liabilities measured at fair value	$ 1,317	$ 2,129

Fair Value Measurements - Conde

Fair Value Measurements - Condensed Consolidated Balance Sheet (Details) - Fair value, Measurements, Recurring - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Assets:
Total assets measured at fair value	$ 879,947	$ 900,641
Liabilities:
Total liabilities measured at fair value	1,317	2,129
Cash equivalents
Assets:
Cash equivalents	546,038	571,280
Short-term investments
Assets:
Short-term investments	268,584	279,133
Prepaid expenses and other
Assets:
Prepaid expenses and other	97	227
Long-term investments
Assets:
Long-term investments	58,895	49,783
Other long-term assets
Assets:
Other long-term assets	6,333	218
Accrued liabilities
Liabilities:
Accrued liabilities	1,317	2,129
Level 1
Assets:
Total assets measured at fair value	476,187	511,355
Liabilities:
Total liabilities measured at fair value	0	0
Level 1 | Cash equivalents
Assets:
Cash equivalents	476,187	511,355
Level 1 | Short-term investments
Assets:
Short-term investments	0	0
Level 1 | Prepaid expenses and other
Assets:
Prepaid expenses and other	0	0
Level 1 | Long-term investments
Assets:
Long-term investments	0	0
Level 1 | Other long-term assets
Assets:
Other long-term assets	0	0
Level 1 | Accrued liabilities
Liabilities:
Accrued liabilities	0	0
Level 2
Assets:
Total assets measured at fair value	403,760	389,286
Liabilities:
Total liabilities measured at fair value	1,317	2,129
Level 2 | Cash equivalents
Assets:
Cash equivalents	69,851	59,925
Level 2 | Short-term investments
Assets:
Short-term investments	268,584	279,133
Level 2 | Prepaid expenses and other
Assets:
Prepaid expenses and other	97	227
Level 2 | Long-term investments
Assets:
Long-term investments	58,895	49,783
Level 2 | Other long-term assets
Assets:
Other long-term assets	6,333	218
Level 2 | Accrued liabilities
Liabilities:
Accrued liabilities	$ 1,317	$ 2,129

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Oct. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 48,356		$ 52,898
Work-in-process	13,253		18,623
Finished goods	165,733		185,488
Deferred cost of goods sold	55,161		61,340
Inventories before provision	282,503		318,349
Provision for excess and obsolescence	(51,165)		(51,206)
Total inventories	231,338		$ 267,143
Provisions	$ 14,977	$ 19,623

Accrued Liabilities and Other50

Accrued Liabilities and Other Short-Term Obligations (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017	Apr. 30, 2017	Oct. 31, 2016
Balance Sheet Related Disclosures [Abstract]
Compensation, payroll related tax and benefits	$ 78,744	$ 113,272
Warranty	43,392	42,456	$ 46,025	$ 52,324
Vacation	42,744	39,778
Capital lease obligations	3,828	3,772
Interest payable	3,602	3,612
Other	97,921	120,044
Total accrued liabilities and other short-term obligations	$ 270,231	$ 322,934

Accrued Liabilities and Other51

Accrued Liabilities and Other Short-Term Obligations - Accrued Warranty (Details) - USD ($) $ in Thousands	6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Movement in Standard Product Warranty Accrual [Roll Forward]
Beginning Balance	$ 42,456	$ 52,324
Current Period Provisions	10,565	2,347
Settlements	(9,629)	(8,646)
Ending Balance	$ 43,392	46,025
Adjustment on prior year provisions		$ (6,300)

Derivative Instruments (Details

Derivative Instruments (Details) - USD ($) $ in Millions	6 Months Ended
	Apr. 30, 2018	Oct. 31, 2017
Foreign Currency Contracts | Designated as hedging instrument | Cash flow hedging
Derivative [Line Items]
Derivative asset, notional amount	$ 114.2	$ 86.1
Derivative maturity (in months)	12 months
Foreign Currency Contracts | Not designated as hedging instrument
Derivative [Line Items]
Derivative asset, notional amount	$ 92.5	83.4
Derivative maturity (in months)	12 months
Interest Rate Swap One | Designated as hedging instrument | Cash flow hedging | Secured debt | Term Loan 2022
Derivative [Line Items]
Interest rate swap fix	98.00%
Derivative, swaption interest rate	4.25%
Interest Rate Swap Two | Designated as hedging instrument | Cash flow hedging | Secured debt | Term Loan 2022
Derivative [Line Items]
Interest rate swap fix	82.00%
Derivative, swaption interest rate	4.25%
Interest Rate Swap Three | Designated as hedging instrument | Cash flow hedging | Secured debt | Term Loan 2022
Derivative [Line Items]
Interest rate swap fix	77.00%
Derivative, swaption interest rate	4.75%
Starting Interest Rate Swap | Designated as hedging instrument | Cash flow hedging | Secured debt | Term Loan 2022
Derivative [Line Items]
Derivative asset, notional amount	$ 387.6	$ 389.6

Accumulated Other Comprehensi53

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income - beginning balance	$ 2,136,342
Accumulated other comprehensive income - ending balance	1,744,119
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income - beginning balance	(11,017)	$ (24,329)
Other comprehensive income (loss) before reclassifications	5,017	1,328
Amounts reclassified from AOCI	928	1,815
Accumulated other comprehensive income - ending balance	(5,072)	(21,186)
Unrealized Gain/(Loss) on Marketable Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income - beginning balance	(451)	139
Other comprehensive income (loss) before reclassifications	(337)	(527)
Amounts reclassified from AOCI	0	0
Accumulated other comprehensive income - ending balance	(788)	(388)
Unrealized Gain (Loss) Derivatives | Foreign Currency Contracts
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income - beginning balance	(1,386)	(1,091)
Other comprehensive income (loss) before reclassifications	4,725	52
Amounts reclassified from AOCI	523	474
Accumulated other comprehensive income - ending balance	(1,421)	(565)
Unrealized Gain (Loss) Derivatives | Starting Interest Rate Swap
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income - beginning balance	218	(5,967)
Other comprehensive income (loss) before reclassifications	(440)	3,556
Amounts reclassified from AOCI	405	1,341
Accumulated other comprehensive income - ending balance	5,466	(1,070)
Cumulative Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income - beginning balance	(9,398)	(17,410)
Other comprehensive income (loss) before reclassifications	1,069	(1,753)
Amounts reclassified from AOCI	0	0
Accumulated other comprehensive income - ending balance	$ (8,329)	$ (19,163)

Short-Term and Long-Term Debt -

Short-Term and Long-Term Debt - 2022 Term Loan Net Carry Value and Estimated Fair Value (Details) - Secured debt - Term Loan Payable due Jan 30, 2022 - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Debt Instrument [Line Items]
Carrying Value	$ 391,566	$ 392,972
Fair Value	$ 397,980

Short-Term and Long-Term Debt55

Short-Term and Long-Term Debt (Details) - USD ($) $ in Thousands	6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Oct. 31, 2017
Secured debt | Term Loan 2022
Debt Instrument [Line Items]
Debt issuance costs, net	$ 2,740		$ 3,100
Amortization of debt issuance costs included in interest expense	400	$ 200
Convertible notes payable | Convertible senior notes due 2018 and 2020
Debt Instrument [Line Items]
Debt issuance costs, net	1,300		$ 2,100
Amortization of debt issuance costs included in interest expense	$ 800	$ 1,000

Short-Term and Long-Term Debt56

Short-Term and Long-Term Debt - 2022 Term Loan Debt Components (Details) - Secured debt - Term Loan 2022 - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Debt Instrument [Line Items]
Principal Balance	$ 396,000
Unamortized Debt Discount	(1,694)
Deferred Debt Issuance Costs	(2,740)	$ (3,100)
Net Carrying Value	$ 391,566	$ 392,972

Short-Term and Long-Term Debt57

Short-Term and Long-Term Debt - Outstanding Convertible Notes Payable Net Carry Value and Estimated Fair Value (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Convertible notes payable
Debt Instrument [Line Items]
Net Carrying Value	$ 547,180	$ 543,009
Fair Value	$ 727,300
3.75% Convertible Senior Notes due October 15, 2018 (Original)
Debt Instrument [Line Items]
Interest rate on convertible notes (as a percent)	3.75%
3.75% Convertible Senior Notes due October 15, 2018 (Original) | Convertible notes payable
Debt Instrument [Line Items]
Net Carrying Value	$ 61,180	61,071
Fair Value	$ 80,907
3.75% Convertible Senior Notes due October 15, 2018 (New)
Debt Instrument [Line Items]
Interest rate on convertible notes (as a percent)	3.75%
3.75% Convertible Senior Notes due October 15, 2018 (New) | Convertible notes payable
Debt Instrument [Line Items]
Net Carrying Value	$ 288,028	287,221
Fair Value	$ 381,268
4.0% Convertible Senior Notes due December 15, 2020
Debt Instrument [Line Items]
Interest rate on convertible notes (as a percent)	4.00%
4.0% Convertible Senior Notes due December 15, 2020 | Convertible notes payable
Debt Instrument [Line Items]
Net Carrying Value	$ 197,972	$ 194,717
Fair Value	$ 265,125

Short-Term and Long-Term Debt58

Short-Term and Long-Term Debt - Outstanding Convertible Notes Payable Debt Components (Details) $ in Thousands	6 Months Ended
	Apr. 30, 2018USD ($)
3.75% Convertible Senior Notes due October 15, 2018 (Original)
Debt Instrument [Line Items]
Interest rate on convertible notes (as a percent)	3.75%
3.75% Convertible Senior Notes due October 15, 2018 (New)
Debt Instrument [Line Items]
Interest rate on convertible notes (as a percent)	3.75%
4.0% Convertible Senior Notes due December 15, 2020
Debt Instrument [Line Items]
Interest rate on convertible notes (as a percent)	4.00%
Convertible notes payable | 3.75% Convertible Senior Notes due October 15, 2018 (Original)
Debt Instrument [Line Items]
Principal Balance	$ 61,270
Unamortized Debt Discount	0
Deferred Debt Issuance Costs	(90)
Net Carrying Value	61,180
Equity component, Net carrying value	0
Convertible notes payable | 3.75% Convertible Senior Notes due October 15, 2018 (New)
Debt Instrument [Line Items]
Principal Balance	288,730
Unamortized Debt Discount	(277)
Deferred Debt Issuance Costs	(425)
Net Carrying Value	288,028
Equity component, Net carrying value	0
Convertible notes payable | 4.0% Convertible Senior Notes due December 15, 2020
Debt Instrument [Line Items]
Principal Balance	206,857
Unamortized Debt Discount	(8,079)
Deferred Debt Issuance Costs	(806)
Net Carrying Value	197,972
Equity component, Net carrying value	$ 43,131
Accretion rate of principal amount	1.85%

Earnings Per Share Calculatio59

Earnings Per Share Calculation - Earnings Per Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017	Oct. 31, 2017	Jul. 31, 2017
Numerator
Net income (loss)	$ 13,856	$ 38,026	$ (459,507)	$ 41,887
Net income (loss) used to calculate Diluted EPS	$ 13,856	$ 42,109	$ (459,507)	$ 42,984
Denominator
Basic weighted average shares outstanding (in shares)	143,975	141,743	143,948	141,223
Add: Shares underlying outstanding stock options and restricted stock units and issuable under employee stock purchase plan (in shares)	1,345	1,317	0	1,409
Dilutive weighted average shares outstanding (in shares)	147,973	165,273	143,948	147,842
EPS
Basic EPS (in dollars per share)	$ 0.10	$ 0.27	$ (3.19)	$ 0.30
Diluted EPS (in dollars per share)	$ 0.09	$ 0.25	$ (3.19)	$ 0.29
0.875% Convertible Senior Notes due June 15, 2017
Numerator
Add: Interest expense associated with convertible senior notes	$ 0	$ 495	$ 0	$ 1,097
Denominator
Add: Shares underlying convertible senior notes (in shares)	0	4,857	0	5,210
EPS
Interest rate on convertible notes (as a percent)					0.875%	0.875%
3.75% Convertible Senior Notes due October 15, 2018 (New)
Denominator
Add: Shares underlying convertible senior notes (in shares)	2,653	0	0	0
EPS
Interest rate on convertible notes (as a percent)	3.75%		3.75%
3.75% Convertible Senior Notes due October 15, 2018 (Original)
Numerator
Add: Interest expense associated with convertible senior notes	$ 0	$ 3,588	$ 0	$ 0
Denominator
Add: Shares underlying convertible senior notes (in shares)	0	17,356	0	0
EPS
Interest rate on convertible notes (as a percent)	3.75%		3.75%

Earnings Per Share Calculatio60

Earnings Per Share Calculation - Antidilutive Securities Excluded (Details) - $ / shares shares in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017	Oct. 31, 2017	Jul. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock average market price (in dollars per share)	$ 24.76		$ 24.76
Total excluded due to anti-dilutive effect (in shares)	12,540	9,923	16,404	27,695
0.875% Convertible Senior Notes due June 15, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Interest rate on convertible notes (as a percent)					0.875%	0.875%
Dilutive conversion spread (in shares)	0	4,857	0	5,210
3.75% Convertible Senior Notes due October 15, 2018 (Original)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Interest rate on convertible notes (as a percent)	3.75%		3.75%
Dilutive conversion spread (in shares)	0	17,356	0	0
3.75% Convertible Senior Notes due October 15, 2018 (New)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Interest rate on convertible notes (as a percent)	3.75%		3.75%
Shares of underlying convertible senior notes due (in shares)			14,300
Dilutive conversion spread (in shares)	2,653	0	0	0
Initial conversion price per share equivalent (in dollars per share)	$ 20.17		$ 20.17
4.0% Convertible Senior Notes due December 15, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Interest rate on convertible notes (as a percent)	4.00%		4.00%
Shares underlying stock options and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total excluded due to anti-dilutive effect (in shares)	304	725	2,496	1,141
Convertible Senior Notes | 3.75% Convertible Senior Notes due October 15, 2018 (Original)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total excluded due to anti-dilutive effect (in shares)	3,038	0	3,038	17,356
Convertible Senior Notes | 3.75% Convertible Senior Notes due October 15, 2018 (New)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive conversion spread (in shares)	2,700
Total excluded due to anti-dilutive effect (in shares)	0	0	1,672	0
Convertible Senior Notes | 4.0% Convertible Senior Notes due December 15, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total excluded due to anti-dilutive effect (in shares)	9,198	9,198	9,198	9,198

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($)	Apr. 30, 2018	Dec. 07, 2017	Oct. 31, 2017
Class of Stock [Line Items]
Effect of adoption of new accounting standard			$ 62,123,000
Deferred tax asset, net	$ 734,824,000		1,155,104,000
Stock repurchase program authorized amount		$ 300,000,000
ASU 2016-09, Excess tax benefit component
Class of Stock [Line Items]
Deferred tax asset, net			62,100,000
Retained earnings
Class of Stock [Line Items]
Effect of adoption of new accounting standard			61,291,000
Retained earnings | ASU 2016-09, Excess tax benefit component
Class of Stock [Line Items]
Effect of adoption of new accounting standard			62,100,000
Retained earnings | ASU 2016-09, Forfeiture rate component
Class of Stock [Line Items]
Effect of adoption of new accounting standard			$ 800,000

Stockholders' Equity - Summary

Stockholders' Equity - Summary of the Stock Repurchase Program (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Apr. 30, 2018USD ($)$ / sharesshares
Shares Repurchased
Cumulative balance at October 31, 2017 (in shares) | shares	0
Repurchase of common stock under the stock repurchase program (in shares) | shares	1,627,233
Cumulative balance at April 30, 2018 (in shares) | shares	1,627,233
Weighted-Average Price per Share
Cumulative balance at October 31, 2017 (in dollars per share) | $ / shares	$ 0
Repurchase of common stock under the stock repurchase program (in dollars per share) | $ / shares	24.06
Cumulative balance at April 30, 2018 (in dollars per share) | $ / shares	$ 24.06
Amount Repurchased (in thousands)
Cumulative balance at October 31, 2017 | $	$ 0
Repurchase of common stock under the stock repurchase program | $	39,147
Cumulative balance at April 30, 2018 | $	$ 39,147

Share-Based Compensation Expe63

Share-Based Compensation Expense - Expense in Period (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense capitalized in inventory, net	$ (45)	$ 35	$ (6)	$ 136
Total share-based compensation	14,166	12,005	26,559	24,830
Cost of Sales
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	1,546	1,387	2,842	2,576
Product costs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	824	708	1,496	1,269
Service costs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	722	679	1,346	1,307
Operating Expense
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	12,665	10,583	23,723	22,118
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	3,796	3,653	7,052	6,862
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	3,760	3,513	7,088	6,386
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 5,109	$ 3,417	$ 9,583	$ 8,870

Share-Based Compensation Expe64

Share-Based Compensation Expense (Details) $ in Millions	6 Months Ended
	Apr. 30, 2018USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized share-based compensation	$ 93
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average period for recognition of share-based compensation (in years)	1 year 7 months 6 days

Segments and Entity-Wide Disc65

Segments and Entity-Wide Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017	Oct. 31, 2017
Segment Reporting Information [Line Items]
Equipment, building, furniture and fixtures, net	$ 298,631		$ 298,631		$ 308,465
Maintenance spares, net	43,200		43,200
Net revenue	729,978	$ 707,022	1,376,113	$ 1,328,519
United States
Segment Reporting Information [Line Items]
Equipment, building, furniture and fixtures, net	81,051		81,051		$ 90,482
Net revenue	392,800	$ 392,000	776,100	$ 771,700
India
Segment Reporting Information [Line Items]
Net revenue	79,400
Networking Platforms
Segment Reporting Information [Line Items]
Other intangible assets, net	34,500		34,500
Software and Software-Related Services
Segment Reporting Information [Line Items]
Other intangible assets, net	$ 56,100		$ 56,100

Segments and Entity-Wide Disc66

Segments and Entity-Wide Disclosures - Revenue, Profit (Loss) and Net Income (Loss) Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Revenue:
Revenue	$ 729,978	$ 707,022	$ 1,376,113	$ 1,328,519
Segment profit:
Operating income (loss)	32,066	57,820	48,802	76,924
Less: Non-performance operating expenses
Selling and marketing	97,359	88,551	185,874	173,553
General and administrative	38,976	34,990	77,382	70,854
Amortization of intangible assets	3,623	10,980	7,246	25,531
Significant asset impairments and restructuring costs	4,359	4,276	10,320	6,671
Add: Other non-performance financial items
Interest expense and other income (loss), net	(11,735)	(16,226)	(23,894)	(31,059)
Less: Provision for income taxes	6,475	3,568	484,415	3,978
Net income (loss)	13,856	38,026	(459,507)	41,887
Operating Segments
Segment profit:
Operating income (loss)	176,383	196,617	329,624	353,533
Operating Segments | Networking Platforms
Revenue:
Revenue	591,682	571,487	1,087,715	1,061,431
Segment profit:
Operating income (loss)	126,823	150,464	215,392	264,210
Operating Segments | Networking Platforms | Converged Packet Optical
Revenue:
Revenue	527,867	505,161	955,297	922,911
Operating Segments | Networking Platforms | Packet Networking
Revenue:
Revenue	63,815	66,326	132,418	138,520
Operating Segments | Software and Software-Related Services
Revenue:
Revenue	38,745	37,716	92,232	77,096
Segment profit:
Operating income (loss)	8,276	4,551	31,911	77,071
Operating Segments | Software and Software-Related Services | Software Platforms
Revenue:
Revenue	12,544	13,143	42,120	30,192
Operating Segments | Software and Software-Related Services | Software-Related Services
Revenue:
Revenue	26,201	24,573	50,112	46,904
Operating Segments | Global Services
Revenue:
Revenue	99,551	97,819	196,166	189,992
Segment profit:
Operating income (loss)	41,284	41,602	82,321	12,252
Operating Segments | Global Services | Maintenance Support and Training
Revenue:
Revenue	60,904	58,241	116,862	113,231
Operating Segments | Global Services | Installation and Deployment
Revenue:
Revenue	28,209	28,695	58,225	56,614
Operating Segments | Global Services | Consulting and Network Design
Revenue:
Revenue	$ 10,438	$ 10,883	$ 21,079	$ 20,147

Segments and Entity-Wide Disc67

Segments and Entity-Wide Disclosures - Geographic Distribution of Equipment, Building, Furniture and Fixtures (Details) - USD ($) $ in Thousands	Apr. 30, 2018	Oct. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Equipment, building, furniture and fixtures, net	$ 298,631	$ 308,465
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Equipment, building, furniture and fixtures, net	197,632	203,491
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Equipment, building, furniture and fixtures, net	81,051	90,482
Other International
Revenues from External Customers and Long-Lived Assets [Line Items]
Equipment, building, furniture and fixtures, net	$ 19,948	$ 14,492

Segments and Entity-Wide Disc68

Segments and Entity-Wide Disclosures - Revenue by Major Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
AT&T | Customer concentration risk | Sales revenue, net
Revenue, Major Customer [Line Items]
Revenue	$ 85,419	$ 107,532	$ 176,065	$ 203,969

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Thousands, $ in Millions	3 Months Ended		6 Months Ended	47 Months Ended
	Apr. 30, 2018USD ($)government_entity	Apr. 30, 2018CAD ($)government_entity	Apr. 30, 2018USD ($)	Mar. 31, 2022USD ($)	Mar. 31, 2022CAD ($)	Apr. 30, 2018CAD ($)
Loss Contingencies [Line Items]
Maximum amount of Canadian grant	$ 45		$ 45			$ 57,600
Number of Canadian government entities	3	3
Benefit from Canadian grant	$ 8.1	$ 10,300
ASEAN country | Customer concentration risk | Sales Revenue, Net
Loss Contingencies [Line Items]
Concentration risk, percentage			1.50%
Scenario, Forecast
Loss Contingencies [Line Items]
Benefit from Canadian grant				$ 2.3	$ 2,950

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Jun. 04, 2018	Apr. 30, 2018
Subsequent Event [Line Items]
Stock repurchases (in shares)		1,627,233
Stock repurchases		$ 39,147
Average price of shares repurchased (in dollars per share)		$ 24.06
Subsequent event
Subsequent Event [Line Items]
Stock repurchases (in shares)	611,942
Stock repurchases	$ 15,400
Average price of shares repurchased (in dollars per share)	$ 25.15
Authorized funds remaining under stock repurchase program	$ 245,500