Juniper Networks (JNPR) 10-Q 7 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Nov. 03, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	JUNIPER NETWORKS INC
Entity Central Index Key	1,043,604
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		374,928,303

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net revenues:
Product	$ 869.7	$ 928.2	$ 2,615.8	$ 2,543.3
Service	388.1	357.1	1,171.9	1,061.2
Total net revenues	1,257.8	1,285.3	3,787.7	3,604.5
Cost of revenues:
Product	336	349.6	1,026.4	955.8
Service	149.4	136.2	440.4	401.9
Total cost of revenues	485.4	485.8	1,466.8	1,357.7
Gross margin	772.4	799.5	2,320.9	2,246.8
Operating expenses:
Research and development	236.4	251.8	752.8	750.7
Sales and marketing	232.5	242.9	716.6	718.4
General and administrative	70.6	54	176.7	172
Restructuring charges	2	0.8	29.4	3.2
Total operating expenses	541.5	549.5	1,675.5	1,644.3
Operating income	230.9	250	645.4	602.5
Other expense, net	(5.1)	(13.4)	(33.8)	(47.2)
Income before income taxes	225.8	236.6	611.6	555.3
Income tax provision	60.1	64.2	157.3	151.5
Net income	$ 165.7	$ 172.4	$ 454.3	$ 403.8
Net income per share:
Basic (in dollars per share)	$ 0.44	$ 0.45	$ 1.20	$ 1.06
Diluted, (in dollars per share)	$ 0.43	$ 0.45	$ 1.18	$ 1.04
Shares used in computing net income per share:
Basic (in shares)	378.3	381	380	382.3
Diluted (in shares)	382.7	384.5	386.5	387.9
Cash dividends declared per common stock (in dollars per share)	$ 0.10	$ 0.10	$ 0.30	$ 0.30

Condensed Consolidated Stateme3

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 165.7	$ 172.4	$ 454.3	$ 403.8
Available-for-sale securities:
Unrealized (losses) gains net of tax benefits of $0.5 and $0.2 during the three and nine months ended September 30, 2017, respectively, and tax provision of $0.3 and benefit of $0.4 for the corresponding periods of the fiscal year ended December 31, 2016 (fiscal 2016), respectively	(0.2)	(0.6)	1.4	5.4
Reclassification adjustment for realized net gains included in net income, net of tax provision of $0.9 during both the three and nine months ended September 2017, respectively, and net of tax provisions of zero and $0.5 for the corresponding periods of fiscal 2016, respectively	(1.9)	(0.3)	(2)	(1.1)
Net change on available-for-sale securities, net of taxes	(2.1)	(0.9)	(0.6)	4.3
Cash flow hedges:
Unrealized gains (loss) net of tax provisions of $0.5 and $3.0, for the three and nine months ended September 30, 2017, respectively, and tax provisions of $0.6 and $1.2 for the corresponding periods of fiscal 2016, respectively	6.3	(0.3)	14.6	3.6
Reclassification adjustment for realized net gains included in net income, net of tax provisions of $0.8 and $1.7 during the three and nine months ended September 30, 2017, respectively, and tax provisions of $0.3 and $0.4 for the corresponding periods of fiscal 2016, respectively	(2.5)	(0.9)	(2.4)	(1)
Net change on cash flow hedges, net of taxes	3.8	(1.2)	12.2	2.6
Change in foreign currency translation adjustments	8.4	(6.9)	19.3	(1.1)
Other comprehensive income (loss), net of taxes	10.1	(9)	30.9	5.8
Comprehensive income	$ 175.8	$ 163.4	$ 485.2	$ 409.6

Condensed Consolidated Stateme4

Condensed Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Unrealized (losses) gains net of tax benefits of $0.5 and $0.2 during the three and nine months ended September 30, 2017, respectively, and tax provision of $0.3 and benefit of $0.4 for the corresponding periods of the fiscal year ended December 31, 2016 (fiscal 2016), respectively	$ 0.5	$ (0.3)	$ 0.2	$ 0.4
Reclassification adjustment for realized net gains included in net income, net of tax provision of $0.9 during both the three and nine months ended September 2017, respectively, and net of tax provisions of zero and $0.5 for the corresponding periods of fiscal 2016, respectively	0.9	0	0.9	0.5
Unrealized gains (loss) net of tax provisions of $0.5 and $3.0, for the three and nine months ended September 30, 2017, respectively, and tax provisions of $0.6 and $1.2 for the corresponding periods of fiscal 2016, respectively	(0.5)	(0.6)	(3)	(1.2)
Reclassification adjustment for realized net gains included in net income, net of tax provisions of $0.8 and $1.7 during the three and nine months ended September 30, 2017, respectively, and tax provisions of $0.3 and $0.4 for the corresponding periods of fiscal 2016, respectively	$ 0.8	$ 0.3	$ 1.7	$ 0.4

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 2,363.7	$ 1,833.2
Short-term investments	922	752.3
Accounts receivable, net of allowances	724.3	1,054.1
Prepaid expenses and other current assets	273.3	332.3
Total current assets	4,283.3	3,971.9
Property and equipment, net	1,007.5	1,063.8
Long-term investments	913.6	1,071.8
Restricted cash and investments	64.9	99.9
Purchased intangible assets, net	133	130.2
Goodwill	3,096.2	3,081.7
Other long-term assets	245.8	237.2
Total assets	9,744.3	9,656.5
Current liabilities:
Accounts payable	205.4	221
Accrued compensation	166.2	233.6
Deferred revenue	977.4	1,032
Other accrued liabilities	236.3	249.3
Total current liabilities	1,585.3	1,735.9
Long-term debt	2,135.7	2,133.7
Long-term deferred revenue	485.5	449.1
Long-term income taxes payable	224	209.2
Other long-term liabilities	155.7	166.1
Total liabilities	4,586.2	4,694
Commitments and contingencies (Note 16)
Stockholders' equity:
Convertible preferred stock, $0.00001 par value; 10.0 shares authorized; none issued and outstanding	0	0
Common stock, $0.00001 par value; 1,000.0 shares authorized; 377.2 shares and 381.1 shares issued and outstanding as of September 30, 2017 and December 31, 2016, respectively	0	0
Additional paid-in capital	8,211	8,281.6
Accumulated other comprehensive loss	(6.4)	(37.3)
Accumulated deficit	(3,046.5)	(3,281.8)
Total stockholders' equity	5,158.1	4,962.5
Total liabilities and stockholders' equity	$ 9,744.3	$ 9,656.5

Condensed Consolidated Balance6

Condensed Consolidated Balance Sheets (Parentheticals) (Unaudited) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Convertible preferred stock - par value (in dollars per share)	$ 0.00001	$ 0.00001
Convertible preferred stock - shares authorized (shares)	10,000,000	10,000,000
Convertible preferred stock - issued (shares)	0	0
Convertible preferred stock - outstanding (shares)	0	0
Common stock - par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock - shares authorized (shares)	1,000,000,000	1,000,000,000
Common stock - issued (shares)	377,200,000	381,100,000
Common stock - outstanding (shares)	377,200,000	381,100,000

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 454.3	$ 403.8
Adjustments to reconcile net income to net cash provided by operating activities:
Share-based compensation expense	151.1	162.1
Depreciation, amortization, and accretion	169.7	151.9
(Gain) loss on investments and disposal of fixed assets, net	(6.7)	1.6
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, net	331.9	36.6
Prepaid expenses and other assets	51.2	(22.2)
Accounts payable	(11.5)	52.1
Accrued compensation	(60.6)	(77)
Income taxes payable	8.8	(7.5)
Other accrued liabilities	(21.1)	(49.8)
Deferred revenue	(21.2)	124.7
Net cash provided by operating activities	1,045.9	776.3
Cash flows from investing activities:
Purchases of property and equipment	(97.6)	(162.9)
Purchases of available-for-sale investments	(1,298.6)	(1,251.9)
Proceeds from sales of available-for-sale investments	761.2	985.1
Proceeds from maturities and redemptions of available-for-sale investments	521.3	232.4
Proceeds from Pulse note receivable	75	0
Purchases of privately-held investments	(9.8)	(17.1)
Proceeds from sales of privately-held investments	1.3	9.5
Purchases of trading investments	(3.9)	(4.3)
Payments for business acquisitions, net of cash and cash equivalents acquired	(33)	(96.7)
Changes in restricted cash	0	(2.4)
Net cash used in investing activities	(84.1)	(308.3)
Cash flows from financing activities:
Purchases and retirement of common stock	(395.5)	(323.9)
Proceeds from issuance of common stock	64.4	59.7
Payment of cash dividends	(113.5)	(114.4)
Payment of debt	0	(300)
Issuance of debt, net	0	494
Payment of financing obligations	0	15.5
Net cash used in financing activities	(444.6)	(200.1)
Effect of foreign currency exchange rates on cash and cash equivalents	13.3	0.2
Net increase in cash and cash equivalents	530.5	268.1
Cash and cash equivalents at beginning of period	1,833.2	1,420.9
Cash and cash equivalents at end of period	$ 2,363.7	$ 1,689

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Basis of Presentation The unaudited Condensed Consolidated Financial Statements of Juniper Networks, Inc. (the “Company” or “Juniper”) have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The Condensed Consolidated Balance Sheet as of December 31, 2016 , has been derived from the audited Consolidated Financial Statements at that date. In the opinion of management, all adjustments, including normal recurring accruals, considered necessary for a fair presentation have been included. The results of operations for the three and nine months ended September 30, 2017 , are not necessarily indicative of the results that may be expected for the year ending December 31, 2017 , or any future period. The information included in this Quarterly Report on Form 10-Q (“Report”) should be read in conjunction with “Management's Discussion and Analysis of Financial Condition and Results of Operations,” “Risk Factors,” “Quantitative and Qualitative Disclosures About Market Risk,” and the Consolidated Financial Statements and footnotes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2016 (the "Form 10-K"). Excess tax benefits from share-based compensation in prior periods have been reclassified to conform to the current-period presentation in the Condensed Consolidated Statements of Cash Flows upon adoption of the accounting standard described in Note 2, Summary of Significant Accounting Policies . In addition, certain other amounts in the Condensed Consolidated Statements of Cash Flows have been reclassified to conform to the current-period presentation. The preparation of the financial statements and related disclosures in accordance with U.S. GAAP requires the Company to make judgments, assumptions, and estimates that affect the amounts reported in the Condensed Consolidated Financial Statements and the accompanying notes. Actual results could differ materially from those estimates under different assumptions or conditions.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Except for the change in certain policies related to share-based compensation upon adoption of the accounting standard described below, there have been no material changes to the Company's significant accounting policies, compared to the accounting policies described in Note 2, Significant Accounting Policies , in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K. Recently Adopted Accounting Standard On January 1, 2017, the Company adopted Financial Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") No. 2016-09 (Topic 718) Compensation—Stock Compensation: Improvements to Employee Share-Based Payment Accounting , which simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, forfeiture, statutory tax withholding requirements, and classification on the statement of cash flows. The impact of the adoption on the Company's Condensed Consolidated Financial Statements was as follows: • Forfeitures: The Company elected to account for forfeitures as they occur using a modified retrospective transition method, rather than estimating forfeitures, resulting in a cumulative-effect adjustment of $9.0 million , which increased the January 1, 2017 opening accumulated deficit balance on the Condensed Consolidated Balance Sheets. • Income tax accounting: The Company is also required to record excess tax benefits and tax deficiencies related to stock- based compensation as income tax benefit or expense in the statement of operations prospectively when share-based awards vest or are settled. Upon adoption, the Company recognized the previously unrecognized excess tax benefits using the modified retrospective transition method, which resulted in no impact to the January 1, 2017 opening accumulated deficit balance as previously unrecognized excess tax effects were fully offset by a valuation allowance. • Cash flow presentation of excess tax benefits: The Company is required to classify excess tax benefits along with other income tax cash flows as an operating activity either prospectively or retrospectively. The Company elected to apply the change in presentation to the statements of cash flows retrospectively and no longer classify the excess tax benefits from share-based compensation as a financing activity. For the nine months ended September 30, 2016, the Company reclassified $5.8 million of excess tax benefits from share-based compensation to operating activities from financing activities. Recent Accounting Standards Not Yet Effective In August 2017, the FASB issued ASU No. 2017-12 (Topic 815) Derivatives and Hedging — Targeted Improvements to Accounting for Hedging Activities, which expands an entity's ability to hedge financial and nonfinancial risk components and amends how companies assess effectiveness as well as changes the presentation and disclosure requirements. The new standard is to be applied on a modified retrospective basis and is effective for interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the impact of adoption on the Consolidated Financial Statements. In May 2017, the FASB issued ASU No. 2017-09 (Topic 718) Compensation—Stock Compensation: Scope of Modification Accounting, which provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting. The new standard is effective on a prospective basis for interim and annual periods beginning after December 15, 2017, with early adoption permitted. In March 2017, the FASB issued ASU No. 2017-08 Receivables—Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities which shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. The ASU will not impact debt securities held at a discount. This standard is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within those annual reporting periods, and is to be applied on a modified retrospective basis with early adoption permitted. The Company is currently evaluating the impact of adoption on the Consolidated Financial Statements. In February 2017, the FASB issued ASU No. 2017-05 Other Income—Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets, which amends guidance on how entities account for the derecognition of a nonfinancial asset or an in substance nonfinancial asset that is not a business. This standard is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within those annual reporting periods, and is to be applied on either a retrospective or modified retrospective basis with early adoption permitted. The adoption of this standard will not have a material impact on the Consolidated Financial Statements. In January 2017, the FASB issued ASU No. 2017-04 (Topic 350) Intangibles—Goodwill and Other: Simplifying the Test for Goodwill Impairmen t, which removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. Under the amended guidance, a goodwill impairment charge will now be recognized for the amount by which the carrying value of a reporting unit exceeds its fair value, not to exceed the carrying amount of goodwill. This ASU will be applied on a prospective basis and is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted for any impairment tests performed after January 1, 2017. In January 2017, the FASB issued ASU No. 2017-01 (Topic 805) Business Combinations: Clarifying the Definition of a Business , which clarifies the definition of a business and assists entities with evaluating when a set of transferred assets and activities is a business. This ASU is effective for interim and annual periods beginning after December 15, 2017, with early adoption permitted and will be applied on a prospective basis. In November 2016, the FASB issued ASU No. 2016-18 (Topic 230) Statement of Cash Flow: Restricted Cash, which provides guidance on the classification of restricted cash to be included with cash and cash equivalents when reconciling the beginning of period and end of period total amounts on the statement of cash flows. The amendments of this ASU are effective for interim and annual periods beginning after December 15, 2017, with early adoption permitted. The standard must be applied retrospectively to all periods presented. The adoption of this standard will not have a material impact on the cash flow activity presented on the Company's Consolidated Statements of Cash Flows. In October 2016, the FASB issued ASU No. 2016-16 (Topic 740) Income Taxes: Intra-Entity Transfers of Assets Other Than Inventory, which requires the recognition of the income tax consequences of an intra-entity transfer of an asset, other than inventory, when the transfer occurs. This ASU will be effective for annual and interim reporting periods beginning after December 15, 2017 and is to be applied on a modified retrospective basis. Early adoption is permitted. The adoption of this standard will not have a material impact on the Consolidated Financial Statements. In August 2016, the FASB issued ASU No. 2016-15 (Topic 230) Statement of Cash Flow: Classification of Certain Cash Receipts and Cash Payments, which clarifies how companies present and classify certain cash receipts and cash payments in the statement of cash flows. This pronouncement is effective for interim and annual reporting periods beginning after December 15, 2017 and will be applied on a retrospective basis. Early adoption is permitted. The adoption of this standard will not have a material impact on the Company's Consolidated Statements of Cash Flows. In June 2016, the FASB issued ASU No. 2016-13 (Topic 326) Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments , which provides more decision-useful information about the expected credit losses on financial instruments and changes the loss impairment methodology. This pronouncement is effective for reporting periods beginning after December 15, 2019, and interim periods within those fiscal years, using a modified retrospective adoption method. Early adoption is permitted. The Company is currently evaluating the impact that this standard will have on its Consolidated Financial Statements and disclosures. In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases , which requires recognition of lease assets and lease liabilities on the balance sheet by lessees for leases classified as operating leases with a lease term of more than twelve months. This ASU should be applied on a modified retrospective basis and is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact of adoption of this standard and has commenced the assessment phase to determine the approach for implementing this standard. The adoption of this standard is expected to have a material impact on the Company's Consolidated Balance Sheets and disclosures. The Company is still evaluating the impact this standard will have on the Consolidated Statements of Operations. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments—Overall: Recognition and Measurement of Financial Assets and Financial Liabilities , which changes how entities measure equity investments and present changes in the fair value of financial liabilities measured under the fair value option. The guidance also updates certain presentation and disclosure requirements. This ASU is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. This ASU is to be applied on a prospective basis for amendments related to equity securities without readily determinable fair values, and all other amendments in this standard will be applied on a modified retrospective basis. For equity securities without readily determinable fair values, we expect to elect the measurement alternative, defined as cost, less impairments, adjusted by observable price changes. The Company does not anticipate that the adoption of the amendments that will be applied on a modified retrospective basis will have a material impact on the Consolidated Financial Statements. In May 2014, the FASB issued ASU No. 2014-09 (Topic 606) —Revenue from Contracts with Customers and several amendments thereafter (“ASU 2014-09”), which provides guidance for revenue recognition that will supersede the revenue recognition requirements in Topic 605, and most industry specific guidance. The core principle for ASU 2014-09 is that revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2017. The Company intends to adopt ASU 2014-09 on January 1, 2018 retrospectively, applying the amendments to each prior reporting period presented and currently remains on schedule with its implementation and the preparation of its prior-period financial statements . Upon adoption, the Company expects a material impact to the opening balance sheet as of January 1, 2016 related to the cumulative effect of adopting this standard, primarily due to the application of the new guidance in the areas of distributor sales, software revenue, contract acquisition costs, variable consideration, and revenue allocation. The Company continues to assess the impact of ASU 2014-09 including any changes to systems, processes, and the control environment as it works through the adoption in 2017, and there remain areas still to be fully concluded upon. In addition, there are ongoing interpretive reviews, which may alter the Company's conclusions on key accounting assessments and the financial impact of ASU 2014-09 on the Company's Consolidated Financial Statements. For further information, refer to Note 2, Significant Accounting Policies , in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K.

Business Combinations

Business Combinations	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Business Combinations	Business Combinations On September 18, 2017 , the Company acquired 100% of Cyphort, Inc. ("Cyphort") for $33.5 million of cash. The acquisition of Cyphort, a software company providing security analytics for advanced threat defense, is expected to strengthen Juniper's security product portfolio. The following table summarizes the estimated fair value of the assets acquired at the acquisition date (in millions, except years): Amount Net tangible assets $ 1.4 Existing technology intangible asset (*) 15.4 Goodwill 16.7 Total $ 33.5 ________________________________ (*) Weighted average estimated useful life of 5 years . Under the terms of the acquisition agreement with Cyphort, the Company assumed certain share-based awards for continuing employees, which were granted in contemplation of future services. The fair value of these share-based awards was $3.8 million , which will be expensed as share-based compensation over the remaining service period. Acquisition-related costs were not material during the three and nine months ended September 30, 2017 and were expensed in the period incurred within general and administrative expense in the Company's Condensed Consolidated Statements of Operations. The operating results of this business combination from the date of acquisition were not material to the Company's consolidated balance sheets and results of operations. Pro forma results of operations for this acquisition have not been presented, as the financial impact to the Company's consolidated results of operations is not material. The primary areas of the preliminary purchase price allocation that are subject to change relate to certain legal and income tax matters.

Cash Equivalents and Investment

Cash Equivalents and Investments	9 Months Ended
	Sep. 30, 2017
Cash Equivalents and Investments [Abstract]
Cash Equivalents and Investments	Cash Equivalents and Investments Investments in Available-for-Sale and Trading Securities The following table summarizes the Company's unrealized gains and losses and fair value of investments designated as available-for-sale and trading securities as of September 30, 2017 and December 31, 2016 (in millions): As of September 30, 2017 As of December 31, 2016 Amortized Gross Unrealized Gross Unrealized Estimated Fair Amortized Gross Unrealized Gross Unrealized Estimated Fair Fixed income securities: Asset-backed securities $ 288.1 $ — $ (0.3 ) $ 287.8 $ 303.0 $ 0.2 $ (0.2 ) $ 303.0 Certificates of deposit 50.0 — — 50.0 66.1 — — 66.1 Commercial paper 124.0 — — 124.0 147.7 — — 147.7 Corporate debt securities 834.1 0.8 (0.8 ) 834.1 846.5 0.4 (2.0 ) 844.9 Foreign government debt securities 64.8 — (0.1 ) 64.7 34.0 — (0.1 ) 33.9 Time deposits 411.4 — — 411.4 264.6 — — 264.6 U.S. government agency securities 156.9 — (0.4 ) 156.5 127.0 — (0.3 ) 126.7 U.S. government securities 548.3 0.1 (0.4 ) 548.0 390.7 0.1 (0.4 ) 390.4 Total fixed income securities 2,477.6 0.9 (2.0 ) 2,476.5 2,179.6 0.7 (3.0 ) 2,177.3 Money market funds 990.7 — — 990.7 592.2 — — 592.2 Mutual funds 8.2 — — 8.2 8.0 — — 8.0 Publicly-traded equity securities — — — — 5.3 — (0.7 ) 4.6 Total available-for-sale securities 3,476.5 0.9 (2.0 ) 3,475.4 2,785.1 0.7 (3.7 ) 2,782.1 Trading securities in mutual funds 26.1 — — 26.1 21.0 — — 21.0 Total $ 3,502.6 $ 0.9 $ (2.0 ) $ 3,501.5 $ 2,806.1 $ 0.7 $ (3.7 ) $ 2,803.1 Reported as: Cash equivalents $ 1,588.8 $ — $ — $ 1,588.8 $ 907.1 $ — $ — $ 907.1 Restricted investments 77.1 — — 77.1 71.9 — — 71.9 Short-term investments 922.3 0.1 (0.4 ) 922.0 753.4 0.1 (1.2 ) 752.3 Long-term investments 914.4 0.8 (1.6 ) 913.6 1,073.7 0.6 (2.5 ) 1,071.8 Total $ 3,502.6 $ 0.9 $ (2.0 ) $ 3,501.5 $ 2,806.1 $ 0.7 $ (3.7 ) $ 2,803.1 The following table presents the contractual maturities of the Company's total fixed income securities as of September 30, 2017 (in millions): Amortized Cost Estimated Fair Value Due in less than one year $ 1,563.2 $ 1,562.9 Due between one and five years 914.4 913.6 Total $ 2,477.6 $ 2,476.5 The following tables present the Company's available-for-sale securities that were in an unrealized loss position as of September 30, 2017 and December 31, 2016 (in millions): As of September 30, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Fixed income securities: Asset-backed securities $ 224.2 $ (0.3 ) $ — $ — $ 224.2 $ (0.3 ) Corporate debt securities 361.6 (0.5 ) 59.5 (0.3 ) 421.1 (0.8 ) Foreign government debt securities 36.6 (0.1 ) — — 36.6 (0.1 ) U.S. government agency securities 89.0 (0.2 ) 18.0 (0.2 ) 107.0 (0.4 ) U.S. government securities 256.3 (0.4 ) 1.8 — 258.1 (0.4 ) Total available-for-sale securities $ 967.7 $ (1.5 ) $ 79.3 $ (0.5 ) $ 1,047.0 $ (2.0 ) As of December 31, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Fixed income securities: Asset-backed securities $ 122.2 $ (0.2 ) $ — $ — $ 122.2 $ (0.2 ) Corporate debt securities 470.8 (1.9 ) 76.7 (0.1 ) 547.5 (2.0 ) Foreign government debt securities 20.3 (0.1 ) — — 20.3 (0.1 ) U.S. government agency securities 106.7 (0.3 ) — — 106.7 (0.3 ) U.S. government securities 254.1 (0.4 ) — — 254.1 (0.4 ) Total fixed income securities 974.1 (2.9 ) 76.7 (0.1 ) 1,050.8 (3.0 ) Publicly-traded equity securities 4.6 (0.7 ) — — 4.6 (0.7 ) Total available-for-sale securities $ 978.7 $ (3.6 ) $ 76.7 $ (0.1 ) $ 1,055.4 $ (3.7 ) The Company had 582 and 494 investments in unrealized loss positions as of September 30, 2017 and December 31, 2016 , respectively. The gross unrealized losses related to these investments were primarily due to changes in market interest rates and stock prices. For available-for-sale debt securities that have unrealized losses, the Company evaluates whether (i) it has the intention to sell any of these investments and (ii) whether it is more likely than not that it will be required to sell any of these investments before recovery of the entire amortized cost basis. As of September 30, 2017 , the Company anticipates that it will recover the entire amortized cost basis of such available-for-sale debt securities and has determined that no other-than-temporary impairments associated with credit losses were required to be recognized during the three and nine months ended September 30, 2017 . During the three and nine months ended September 30, 2016 , there were no other-than-temporary impairments associated with these investments. During the three and nine months ended September 30, 2017 and September 30, 2016 , there were no material gross realized gains or losses from either available-for-sale securities or from trading securities. Restricted Cash and Investments There have been no material changes to the composition of the Company's restricted cash and investments as described in Note 4, Cash Equivalents and Investments , in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K. The restricted investments are designated as available-for-sale securities except relating to the non-qualified deferred compensation plan which are designated as trading securities. As of September 30, 2017 , total restricted cash and investments was $123.2 million , of which $58.3 million was included in prepaid expenses and other current assets and $64.9 million was included in restricted cash and investments on the Condensed Consolidated Balance Sheets. Investments in Privately-Held Companies As of September 30, 2017 and December 31, 2016 , the carrying values of the Company's investments in privately-held companies of $72.5 million and $62.7 million , respectively, were included in other long-term assets in the Condensed Consolidated Balance Sheets. These investments include debt and redeemable preferred stock securities that are carried at fair value, and non-redeemable preferred stock and common stock securities that are carried at cost. As of September 30, 2017 and December 31, 2016 , the carrying value of the investments accounted for under the cost method were $30.2 million and $19.0 million , respectively. See Note 5, Fair Value Measurements , for the Company's investments in privately-held companies that are carried at fair value. The Company adjusts the carrying value for its investments in privately-held companies that are carried at cost for any impairment if the fair value is less than the carrying value of the respective assets on an other-than-temporary basis. There were no impairment charges for the three and nine months ended September 30, 2017 . During the three and nine months ended September 30, 2016 , the Company determined that certain investments in privately-held companies were other than-temporarily impaired, resulting in impairment charges of $4.5 million and $9.6 million , that were recorded within other expense, net in the Condensed Consolidated Statement of Operations.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Recurring Basis The following table provides a summary of assets and liabilities measured at fair value on a recurring basis and as reported in the Condensed Consolidated Balance Sheets (in millions): Fair Value Measurements at Fair Value Measurements at Quoted Prices in Significant Other Significant Other Total Quoted Prices in Significant Other Significant Other Total Assets: Available-for-sale securities: Asset-backed securities $ — $ 287.8 $ — $ 287.8 $ — $ 303.0 $ — $ 303.0 Certificates of deposit — 50.0 — 50.0 — 66.1 — 66.1 Commercial paper — 124.0 — 124.0 — 147.7 — 147.7 Corporate debt securities — 834.1 — 834.1 — 844.9 — 844.9 Foreign government debt securities — 64.7 — 64.7 — 33.9 — 33.9 Money market funds 990.7 — — 990.7 592.2 — — 592.2 Mutual funds 8.2 — — 8.2 8.0 — — 8.0 Publicly-traded equity securities — — — — 4.6 — — 4.6 Time deposits — 411.4 — 411.4 — 264.6 — 264.6 U.S. government agency securities — 156.5 — 156.5 — 126.7 — 126.7 U.S. government securities 343.7 204.3 — 548.0 345.0 45.4 — 390.4 Total available-for-sale securities 1,342.6 2,132.8 — 3,475.4 949.8 1,832.3 — 2,782.1 Trading securities in mutual funds 26.1 — — 26.1 21.0 — — 21.0 Privately-held debt and redeemable preferred stock securities — — 42.3 42.3 — — 43.7 43.7 Derivative assets: Foreign exchange contracts — 8.5 — 8.5 — 0.9 — 0.9 Total assets measured at fair value $ 1,368.7 $ 2,141.3 $ 42.3 $ 3,552.3 $ 970.8 $ 1,833.2 $ 43.7 $ 2,847.7 Liabilities: Derivative liabilities: Foreign exchange contracts $ — $ (0.6 ) $ — $ (0.6 ) $ — $ (4.9 ) $ — $ (4.9 ) Total liabilities measured at fair value $ — $ (0.6 ) $ — $ (0.6 ) $ — $ (4.9 ) $ — $ (4.9 ) Total assets, reported as: Cash equivalents $ 947.9 $ 640.9 $ — $ 1,588.8 $ 549.4 $ 357.7 $ — $ 907.1 Restricted investments 77.1 — — 77.1 71.9 — — 71.9 Short-term investments 231.9 690.1 — 922.0 178.0 574.3 — 752.3 Long-term investments 111.8 801.8 — 913.6 171.5 900.3 — 1,071.8 Prepaid expenses and other current assets — 8.5 — 8.5 — 0.9 — 0.9 Other long-term assets — — 42.3 42.3 — — 43.7 43.7 Total assets measured at fair value $ 1,368.7 $ 2,141.3 $ 42.3 $ 3,552.3 $ 970.8 $ 1,833.2 $ 43.7 $ 2,847.7 Total liabilities, reported as: Other accrued liabilities $ — $ (0.6 ) $ — $ (0.6 ) $ — $ (4.9 ) $ — $ (4.9 ) Total liabilities measured at fair value $ — $ (0.6 ) $ — $ (0.6 ) $ — $ (4.9 ) $ — $ (4.9 ) The Company's Level 2 available-for-sale fixed income securities are priced using quoted market prices for similar instruments or non-binding market prices that are corroborated by observable market data. The Company uses inputs such as actual trade data, benchmark yields, broker/dealer quotes, or alternative pricing sources with reasonable levels of price transparency which are obtained from quoted market prices, independent pricing vendors, or other sources, to determine the ultimate fair value of these assets. The Company's derivative instruments are classified as Level 2, as they are not actively traded and are valued using pricing models that use observable market inputs. The Company's policy is to recognize asset or liability transfers among Level 1, Level 2, and Level 3 at the beginning of the quarter in which a change in circumstances resulted in a transfer. During the three and nine months ended September 30, 2017 , the Company had no transfers between levels of the fair value hierarchy of its assets or liabilities measured at fair value. All of the Company's privately-held debt and redeemable preferred stock securities are classified as Level 3 assets due to the lack of observable inputs to determine fair value. The Company estimates the fair value of its privately-held debt and redeemable preferred stock securities on a recurring basis using an analysis of the financial condition and near-term prospects of the investee, including recent financing activities and the investee's capital structure. During the three and nine months ended September 30, 2017 , there were no purchases, sales, gains, or losses related to privately-held debt and redeemable preferred stocks securities. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis As of September 30, 2017 , the Company had no assets required to be measured at fair value on a nonrecurring basis. Investments in privately-held companies, which are normally carried at cost, are measured at fair value on a nonrecurring basis due to events and circumstances that the Company identifies as materially impacting the carrying value of the investments. As of December 31, 2016 , certain investments in privately-held companies with a carrying value of $1.6 million were impaired and written-down to their fair value of zero and were classified as Level 3 assets due to lack of observable inputs to determine fair value. The Company estimates the fair value of its investments in privately-held companies using an analysis of the financial condition and near-term prospects of the investee, including recent financing activities and the investee's capital structure. The impairment charge was recorded to other expense, net in the Condensed Consolidated Statements of Operations. As of September 30, 2017 and December 31, 2016 , the Company had no liabilities required to be measured at fair value on a nonrecurring basis. Assets and Liabilities Not Measured at Fair Value The carrying amounts of the Company's accounts receivable, accounts payable, and other accrued liabilities approximate fair value due to their short maturities. As of September 30, 2017 and December 31, 2016 , the estimated fair value of the Company's long-term debt in the Condensed Consolidated Balance Sheets was $2,274.8 million and $2,215.7 million , respectively, based on observable market inputs (Level 2). The carrying value of the promissory note issued to the Company in connection with the previously completed sale of Junos Pulse (the “Pulse Note”), of $58.5 million and $132.9 million approximates its fair value as of September 30, 2017 and December 31, 2016 . The Pulse Note is classified as a Level 3 asset due to the lack of observable inputs to determine fair value. See Note 8, Other Financial Information , for further information on the Pulse Note.

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments The Company uses derivatives to partially offset its market exposure to fluctuations in certain foreign currencies and does not enter into derivatives for speculative or trading purposes. The notional amount of the Company's foreign currency derivatives are summarized as follows (in millions): As of September 30, December 31, Cash flow hedges $ 231.6 $ 172.0 Non-designated derivatives 147.1 — Total $ 378.7 $ 172.0 Cash Flow Hedges The Company uses foreign currency forwards to hedge the Company's planned cost of revenues and operating expenses denominated in foreign currencies. These derivatives are designated as cash flow hedges. Execution of cash flow hedge derivatives typically occurs every month with maturities of eighteen months or less. As of September 30, 2017 , an estimated $8.8 million of existing gains or losses within accumulated other comprehensive loss is expected to be reclassified into earnings within the next 12 months. The Company recognized an unrealized gain of $6.8 million and $17.6 million in accumulated other comprehensive loss for the effective portion of its derivative instruments for the three and nine months ended September 30, 2017 , respectively; and unrealized gains of $0.3 million and $4.8 million for the corresponding periods of the fiscal year ended December 31, 2016, respectively. The amounts reclassified out of accumulated other comprehensive loss to cost of revenues and operating expense in the Condensed Consolidated Statements of Operations was not material during the three and nine months ended September 30, 2017 and September 30, 2016 . The ineffective portion of the Company's derivative instruments recognized in its Condensed Consolidated Statements of Operations was not material during the three and nine months ended September 30, 2017 and September 30, 2016 . See Note 5, Fair Value Measurements , for the fair values of the Company's derivative instruments in the Condensed Consolidated Balance Sheets. Non-Designated Derivatives The Company also uses foreign currency forward contracts to mitigate variability in gains and losses generated from the remeasurement of certain monetary assets and liabilities denominated in foreign currencies. These foreign exchange forward contracts typically have maturities of approximately one month . The outstanding non-designated derivative instruments are carried at fair value. Changes in the fair value of these derivatives recorded in other expense, net within the Condensed Consolidated Statements of Operations were not material during the three and nine months ended September 30, 2017 and September 30, 2016 .

Goodwill and Purchased Intangib

Goodwill and Purchased Intangible Assets	9 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Purchased Intangible Assets	Goodwill and Purchased Intangible Assets Goodwill The following table presents goodwill activity (in millions): Balance as of December 31, 2016 $ 3,081.7 Additions due to business combination 16.7 Other (*) (2.2 ) Balance as of September 30, 2017 $ 3,096.2 ________________________________ (*) Other primarily consists of certain purchase accounting adjustments related to previously completed business combinations. Purchased Intangible Assets The Company’s purchased intangible assets as of September 30, 2017 and December 31, 2016 , were $133.0 million and $130.2 million , respectively. The balance as of September 30, 2017 includes $15.4 million of purchased intangible assets related to the acquisition of Cyphort. See Note 3 , Business Combinations , for further details. Amortization expense was $4.1 million and $12.6 million during the three and nine months ended September 30, 2017 , respectively, and $4.8 million and $12.9 million during the three and nine months ended September 30, 2016 , respectively.

Other Financial Information

Other Financial Information	9 Months Ended
	Sep. 30, 2017
Other Financial Information [Abstract]
Other Financial Information	Other Financial Information Inventory Total inventory consisted of the following (in millions): As of September 30, December 31, Production and service materials $ 72.6 $ 75.6 Finished goods 18.3 19.9 Inventory $ 90.9 $ 95.5 Reported as: Prepaid expenses and other current assets $ 84.9 $ 91.4 Other long-term assets 6.0 4.1 Total $ 90.9 $ 95.5 Note Receivable In October 2014, the Company completed the sale of its Junos Pulse product portfolio. The Company received total consideration of $230.7 million , of which $105.7 million was in cash, net of a $19.3 million working capital adjustment, and $125.0 million was in the form of a non-contingent interest-bearing promissory note due to the Company on April 1, 2016. In October 2015, the Company and the issuer of the Pulse Note mutually agreed to amend the original terms of the Pulse Note to, among other things: • extend the maturity date from April 1, 2016 to December 31, 2018; • provide that interest due on the Pulse Note through December 31, 2015 shall be paid in kind by increasing the outstanding principal amount of the note and increase the interest rate on the Pulse Note; and • require a minimum payment of $75.0 million on or prior to April 1, 2017, less any principal amount previously pre-paid to the Company. In May 2017, the Company received payment of $75.0 million and the outstanding interest due. The Company and the issuer of the Pulse Note further mutually agreed to amend the terms of the Pulse Note to, among other things: • extend the maturity date of the remaining outstanding amount of approximately $58.0 million from December 31, 2018 to September 30, 2022; • provide that interest due after April 1, 2017 can be paid in kind by increasing the outstanding principal amount of the note or paid in cash; • require the promissory note to be subordinated to other debt raised by the issuer; and • entitle the Company to additional financial considerations if the issuer of the note and its affiliates meet certain conditions. The Company considers notes receivable to be impaired when, based on current information and events, it is probable that the Company will not be able to collect the scheduled payments of principal or interest when due. No impairment charge was required for the Pulse Note as of September 30, 2017 . The outstanding balance of the Pulse Note, along with the accumulated interest paid in kind, of $58.5 million as of September 30, 2017 is classified as a long-term asset based on expected collection beyond twelve months from the Condensed Consolidated Balance Sheet date. During the three and nine months ended September 30, 2017 , the interest income on the Pulse Note was $1.6 million and $6.5 million , respectively. During the three and nine months ended and September 30, 2016 , the related amount of interest income recognized was $2.7 million and $8.0 million , respectively. Warranties Changes during the nine months ended September 30, 2017 in the Company’s warranty reserve as reported within other accrued liabilities in the Condensed Consolidated Balance Sheets were as follows (in millions): Balance as of December 31, 2016 $ 41.3 Provisions made during the period 29.6 Actual costs incurred during the period (41.5 ) Balance as of September 30, 2017 $ 29.4 Deferred Revenue Details of the Company's deferred revenue, as reported in the Condensed Consolidated Balance Sheets, were as follows (in millions): As of September 30, December 31, Deferred product revenue: Undelivered product commitments and other product deferrals $ 309.3 $ 302.4 Distributor inventory and other sell-through items 61.9 74.2 Deferred gross product revenue 371.2 376.6 Deferred cost of product revenue (47.5 ) (53.7 ) Deferred product revenue, net 323.7 322.9 Deferred service revenue 1,139.2 1,158.2 Total $ 1,462.9 $ 1,481.1 Reported as: Current $ 977.4 $ 1,032.0 Long-term 485.5 449.1 Total $ 1,462.9 $ 1,481.1 Other Expense, Net Other expense, net, consisted of the following (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Interest income $ 14.7 $ 9.1 $ 37.1 $ 25.5 Interest expense (25.3 ) (25.1 ) (75.6 ) (72.6 ) Gain on investments, net 4.7 1.9 6.7 0.1 Other 0.8 0.7 (2.0 ) (0.2 ) Other expense, net $ (5.1 ) $ (13.4 ) $ (33.8 ) $ (47.2 )

Restructuring Charges

Restructuring Charges	9 Months Ended
	Sep. 30, 2017
Restructuring and Related Activities [Abstract]
Restructuring Charges	Restructuring Charges During the first quarter of 2017, the Company initiated a restructuring plan (the “2017 Restructuring Plan”) to realign its workforce and increase operational efficiencies. During the second quarter of 2017, the Company undertook certain further actions under the 2017 Restructuring Plan, resulting in additional severance and contract termination costs that were recorded to restructuring charges in the Condensed Consolidated Statement of Operations. During the three and nine months ended September 30, 2017 , the Company recorded $0.6 million and $26.0 million of severance costs, and $1.4 million and $3.4 million of contract terminations, respectively, that were recorded to restructuring charges in the Condensed Consolidated Statement of Operations. See Note 17, Subsequent Events, for discussion of the Company's restructuring activity subsequent to September 30, 2017 . Restructuring liabilities are reported within other accrued liabilities in the Condensed Consolidated Balance Sheets. The following table provides a summary of changes in the restructuring liabilities primarily related to the 2017 Restructuring Plan initiated in February 2017 (in millions): December 31, 2016 (*) Charges Cash Payments Other September 30, Severance $ 0.7 $ 26.0 $ (25.5 ) $ (0.1 ) $ 1.1 Contract terminations and other 0.5 3.4 (0.4 ) 0.1 3.6 Total $ 1.2 $ 29.4 $ (25.9 ) $ — $ 4.7 ________________________________ (*) Consists of costs in connection with a prior restructuring plan that is substantially complete.

Debt and Financing

Debt and Financing	9 Months Ended
	Sep. 30, 2017
Debt Instruments [Abstract]
Debt and Financing	Debt and Financing Debt The Company's long-term debt is summarized as follows (in millions, except percentages): As of September 30, 2017 Amount Effective Interest Rates Senior Notes ("Notes"): 3.125% fixed-rate notes, due February 2019 $ 350.0 3.36 % 3.300% fixed-rate notes, due June 2020 300.0 3.47 % 4.600% fixed-rate notes, due March 2021 300.0 4.69 % 4.500% fixed-rate notes, due March 2024, issued March 2014 350.0 4.63 % 4.500% fixed-rate notes, due March 2024, issued February 2016 150.0 4.87 % 4.350% fixed-rate notes, due June 2025 300.0 4.47 % 5.950% fixed-rate notes, due March 2041 400.0 6.03 % Total senior notes 2,150.0 Unaccreted discount and debt issuance costs (14.3 ) Total $ 2,135.7 The Notes above are the Company’s senior unsecured and unsubordinated obligations, ranking equally in right of payment to all of the Company’s existing and future senior unsecured and unsubordinated indebtedness and senior in right of payment to any of the Company’s future indebtedness that is expressly subordinated to the Notes. Interest on the Notes is payable in cash semiannually. The Company may redeem, either in whole or in part, the Senior Notes due 2020 at any time on or after May 15, 2020, the Senior Notes due 2025 at any time on or after March 15, 2025, and the other Notes at any time, in each case, according to the terms of the indentures governing the Notes. In the event of a change of control repurchase event, the holders of the Notes may require the Company to repurchase for cash all or part of the Notes at a purchase price equal to 101% of the aggregate principal amount, plus accrued and unpaid interest, if any. The indentures that govern the Notes also contain various covenants, including limitations on the Company's ability to incur liens or enter into sale-leaseback transactions over certain dollar thresholds. As of September 30, 2017 , the Company was in compliance with all covenants in the indentures governing the Notes. Revolving Credit Facility In June 2014, the Company entered into a Credit Agreement (“Credit Agreement”) with certain institutional lenders that provides for a $500.0 million unsecured revolving credit facility, with an option to increase the amount of the credit facility by up to an additional $200.0 million , subject to certain conditions. Revolving loans may be borrowed, repaid and reborrowed until June 27, 2019, at which time all amounts borrowed must be repaid. Borrowings under the Credit Agreement will bear interest at either i) a floating rate per annum equal to the base rate plus a margin of between 0.00% and 0.50% , depending on the Company's public debt rating or ii) a per annum rate equal to the reserve adjusted Eurocurrency rate , plus a margin of between 0.90% and 1.50% , depending on the Company's public debt rating. As of September 30, 2017 , the Company was in compliance with all covenants in the Credit Agreement, and no amounts were outstanding. Financing Arrangements The Company provides certain customers with access to extended financing arrangements that allow for longer payment terms than those typically provided by the Company by factoring accounts receivable to third-party financing providers (“financing providers”). The program does not and is not intended to affect the timing of the Company's revenue recognition. Under the financing arrangements, proceeds from the financing providers are due to the Company within 1 to 90 days from the sale of the receivable. In these transactions with the financing providers, the Company surrenders control over the transferred assets. Pursuant to the financing arrangements for the sale of receivables, the Company sold net receivables of $77.3 million and $132.6 million during the three and nine months ended September 30, 2017 , respectively, and $59.3 million and $73.4 million during the three and nine months ended September 30, 2016 , respectively. The Company received cash proceeds from financing providers of $57.6 million and $113.3 million during the three and nine months ended September 30, 2017 , respectively, and $30.0 million and $40.8 million during the three and nine months ended September 30, 2016 , respectively. As of September 30, 2017 and December 31, 2016 , the amounts owed by the financing providers were $32.9 million and $13.6 million , respectively, which were recorded in accounts receivable in the Condensed Consolidated Balance Sheets.

Equity

Equity	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Equity	Equity Cash Dividends on Shares of Common Stock During the nine months ended September 30, 2017 , the Company declared a quarterly cash dividend of $0.10 per share of common stock on January 26, 2017, April 25, 2017 and July 25, 2017, which was paid on March 22, 2017, June 22, 2017 and September 22, 2017, respectively, to stockholders of record on March 1, 2017, June 1, 2017, and September 1, 2017, respectively, in the aggregate amount of $113.5 million . Any future dividends, and the establishment of record and payment dates, are subject to approval by the Board of Directors (the “Board”) of the Company or an authorized committee thereof. See Note 17, Subsequent Events, for discussion of the Company's dividend declaration subsequent to September 30, 2017 . Stock Repurchase Activities In 2014 and 2015, the Board approved a stock repurchase program that authorized the Company to repurchase up to $2.1 billion of its common stock, including $1.2 billion pursuant to an accelerated share repurchase program, and subsequent increases to the authorization totaling $1.8 billion (“Stock Repurchase Program”). In February 2017, the Board authorized an additional $500.0 million increase to the Stock Repurchase Program for a total of $4.4 billion . The following table summarizes the Company's repurchases and retirements of its common stock under its Stock Repurchase Program (in millions, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Shares repurchased 5.0 4.9 13.5 13.5 Average price per share $ 28.16 $ 23.04 $ 28.85 $ 23.25 Amount repurchased $ 140.0 $ 112.4 $ 390.0 $ 312.9 As of September 30, 2017 , there was $329.7 million of authorized funds remaining under the Stock Repurchase Program. Future share repurchases under the Stock Repurchase Program will be subject to a review of the circumstances at that time and will be made from time to time in private transactions or open market purchases as permitted by securities laws and other legal requirements. The Stock Repurchase Program may be discontinued at any time. See Note 17, Subsequent Events, for discussion of the Company's stock repurchase activity subsequent to September 30, 2017 . In addition to repurchases under the Stock Repurchase Program, the Company also repurchases common stock from certain employees in connection with the net issuance of shares to satisfy minimum tax withholding obligations upon the vesting of certain stock awards issued to such employees. Repurchases associated with tax withholdings were not material during the three and nine months ended September 30, 2017 . Repurchases associated with tax withholdings were $1.4 million and $11.0 million for the three and nine months ended September 30, 2016 . Accumulated Other Comprehensive Loss, Net of Tax The components of accumulated other comprehensive loss, net of related taxes, for the nine months ended September 30, 2017 were as follows (in millions): Unrealized Gains (Losses) on Available-for- Sale Securities (1) Unrealized (Losses) Gains on Cash Flow Hedges (2) Foreign Currency Translation Adjustments Total Balance as of December 31, 2016 $ 16.6 $ (4.5 ) $ (49.4 ) $ (37.3 ) Other comprehensive gains before reclassifications 1.4 14.6 19.3 35.3 Amount reclassified from accumulated other comprehensive loss (2.0 ) (2.4 ) — (4.4 ) Other comprehensive (loss) gains, net (0.6 ) 12.2 19.3 30.9 Balance as of September 30, 2017 $ 16.0 $ 7.7 $ (30.1 ) $ (6.4 ) ________________________________ (1) The reclassifications out of accumulated other comprehensive loss during the nine months ended September 30, 2017 for realized gains on available-for-sale securities were not material, and were included in other expense, net, in the Condensed Consolidated Statements of Operations. (2) The reclassifications out of accumulated other comprehensive loss during the nine months ended September 30, 2017 for realized gains on cash flow hedges were not material, and were included within cost of revenues, research and development, sales and marketing, and general and administrative in the Condensed Consolidated Statements of Operations.

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Employee Benefit Plans	Employee Benefit Plans Equity Incentive Plans The Company has stock-based compensation plans pursuant to which it has granted stock options, restricted stock units (“RSUs”), and performance share awards (“PSAs”). The Company also maintains the Company's 2008 Employee Stock Purchase Plan (the “ESPP”) for all eligible employees. As of September 30, 2017 , 35.3 million and 11.2 million shares were available for future issuance under the Company's 2015 Equity Incentive Plan (the "2015 Plan") and the ESPP, respectively, which includes an additional 23.0 million shares under the 2015 Plan and 9.0 million shares under the ESPP that were approved by the Company's stockholders in May 2017. Stock Option Activities The following table summarizes the Company’s stock option activity and related information as of and for the nine months ended September 30, 2017 (in millions, except for per share amounts and years): Outstanding Options Number of Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance as of December 31, 2016 2.4 $ 29.20 Exercised (0.5 ) 14.97 Expired/Canceled (0.8 ) 31.09 Balance as of September 30, 2017 1.1 $ 34.31 1.1 $ 3.1 As of September 30, 2017: Vested and expected-to-vest options 1.1 $ 34.31 1.1 $ 3.1 Exercisable options 1.0 $ 35.56 0.8 $ 2.1 Restricted Stock Unit, Restricted Stock Award, and Performance Share Award Activities The Company’s RSU, restricted stock award ("RSA"), and PSA activity and related information as of and for the nine months ended September 30, 2017 were as follows (in millions, except per share amounts and years): Outstanding RSUs, RSAs, and PSAs Number of Shares Weighted Average Grant-Date Fair Value per Share Weighted Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance as of December 31, 2016 20.9 $ 24.05 RSUs granted (1)(3) 6.6 27.56 RSUs assumed in acquisitions 0.1 26.91 PSAs granted (2)(3) 0.6 27.37 RSUs vested (6.0 ) 23.81 RSAs vested (0.4 ) 22.80 PSAs vested (0.5 ) 24.29 RSUs canceled (1.5 ) 24.57 PSAs canceled (0.5 ) 25.11 Balance as of September 30, 2017 19.3 $ 25.23 1.1 $ 537.1 ________________________________ (1) Includes service-based and market-based RSUs. (2) The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee of the Board are achieved at target is 0.4 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 0.6 million shares. (3) The grant date fair value of RSUs and PSAs were reduced by the present value of dividends expected to be paid on the underlying shares of common stock during the requisite and derived service period as these awards are not entitled to receive dividends until vested. During the nine months ended September 30, 2017 , the Company declared a quarterly cash dividend of $0.10 per share of common stock on January 26, 2017, April 25, 2017, and July 25, 2017. Employee Stock Purchase Plan The ESPP is implemented in a series of offering periods, each currently six months in duration, or such other period as determined by the Board. Employees purchased approximately 1.2 million and 2.7 million shares of common stock through the ESPP at an average exercise price of $22.79 and $20.83 per share during the three and nine months ended September 30, 2017 , respectively. Employees purchased approximately 1.4 million and 2.7 million shares of common stock through the ESPP at an average exercise price of $19.29 and $19.66 per share during the three and nine months ended September 30, 2016 , respectively. Share-Based Compensation Expense Share-based compensation expense associated with stock options, RSUs, RSAs, PSAs, and ESPP was recorded in the following cost and expense categories in the Condensed Consolidated Statements of Operations (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cost of revenues - Product $ 1.5 $ 1.5 $ 3.8 $ 4.9 Cost of revenues - Service 3.9 3.5 13.5 11.3 Research and development 18.5 27.2 67.4 89.0 Sales and marketing 13.7 17.5 45.3 40.7 General and administrative 7.4 5.9 21.1 17.1 Total $ 45.0 $ 55.6 $ 151.1 $ 163.0 The following table summarizes share-based compensation expense by award type (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Stock options $ 0.2 $ 1.5 $ 0.5 $ 3.7 RSUs, RSAs, and PSAs 41.0 50.3 138.9 147.6 ESPP 3.8 3.8 11.7 11.7 Total $ 45.0 $ 55.6 $ 151.1 $ 163.0 As of September 30, 2017 , the unrecognized compensation cost related to unvested stock options, RSUs, RSAs, and PSAs was $309.8 million to be recognized over a weighted-average period of 1.6 years.

Segments

Segments	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Segments	Segments The Company operates in one reportable segment. Our chief operating decision maker reviews financial information presented on a consolidated basis for purposes of allocating resources and evaluating financial performance, accompanied by disaggregated information about net revenues by product and service, customer vertical, and geographic region as presented below. The following table presents net revenues by product and service (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Routing $ 585.8 $ 620.2 $ 1,679.9 $ 1,699.0 Switching 212.6 222.5 730.2 607.2 Security 71.3 85.5 205.7 237.1 Total product 869.7 928.2 2,615.8 2,543.3 Total service 388.1 357.1 1,171.9 1,061.2 Total $ 1,257.8 $ 1,285.3 $ 3,787.7 $ 3,604.5 In the first quarter of 2017, the Company began reporting revenue on the following key customer verticals: Cloud, Telecom/Cable, and Strategic Enterprise. A summary of the types of customers included in these verticals is as follows: • Cloud: companies that are heavily reliant on the cloud for their business model’s success. As an example, customers in the cloud vertical can include cloud service providers as well as enterprises that provide software-as-a-service, infrastructure-as-a-service, or platform-as-a-service. • Telecom/Cable: includes wireline and wireless carriers and cable operators. • Strategic Enterprise: generally is comprised of financial services; national, federal, state, and local governments; research and educational institutions, and enterprises not represented in the Cloud vertical. The following table presents net revenues by customer vertical (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cloud $ 344.9 $ 359.4 $ 1,056.1 $ 911.5 Telecom/Cable 576.9 599.4 1,707.8 1,688.5 Strategic Enterprise 336.0 326.5 1,023.8 1,004.5 Total $ 1,257.8 $ 1,285.3 $ 3,787.7 $ 3,604.5 The Company attributes revenues to geographic region based on the customer’s shipping address. The following table presents net revenues by geographic region (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Americas: United States $ 668.8 $ 684.6 $ 2,076.0 $ 1,924.9 Other 60.4 60.4 165.6 168.3 Total Americas 729.2 745.0 2,241.6 2,093.2 Europe, Middle East, and Africa 298.6 338.0 871.3 923.5 Asia Pacific 230.0 202.3 674.8 587.8 Total $ 1,257.8 $ 1,285.3 $ 3,787.7 $ 3,604.5

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table provides details of income taxes (in millions, except percentages): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Income before income taxes $ 225.8 $ 236.6 $ 611.6 $ 555.3 Income tax provision $ 60.1 $ 64.2 $ 157.3 $ 151.5 Effective tax rate 26.6 % 27.1 % 25.7 % 27.3 % The Company's effective tax rates during the three and nine months ended September 30, 2017 and September 30, 2016 , differ from the statutory rate primarily due to the benefit of the Section 199 deduction for U.S. production activities, the federal research and development credit, and earnings in foreign jurisdictions, which are subject to lower tax rates. Additionally, the Company's effective tax rates for the three and nine months ended September 30, 2017 were also impacted by the benefit from restructuring charges and excess tax benefits related to share-based compensation. As of September 30, 2017 , the total amount of gross unrecognized tax benefits was $236.7 million , of which $204.2 million , if recognized, would favorably affect the Company's effective tax rate. T he Company engages in continuous discussions and negotiations with tax authorities regarding tax matters in various jurisdictions. It is reasonably possible that the balance of unrecognized tax benefits could decrease up to $67.0 million within the next twelve months due to lapses of applicable statutes of limitations and the completion of tax review cycles in various tax jurisdictions. The balance primarily relates to matters involving U.S and non-U.S taxation of cross-border transactions and the utilization of losses.

Net Income Per Share

Net Income Per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Net Income Per Share	Net Income per Share The Company computed basic and diluted net income per share as follows (in millions, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Numerator: Net income $ 165.7 $ 172.4 $ 454.3 $ 403.8 Denominator: Weighted-average shares used to compute basic net income per share 378.3 381.0 380.0 382.3 Dilutive effect of employee stock awards 4.4 3.5 6.5 5.6 Weighted-average shares used to compute diluted net income per share 382.7 384.5 386.5 387.9 Net income per share Basic $ 0.44 $ 0.45 $ 1.20 $ 1.06 Diluted $ 0.43 $ 0.45 $ 1.18 $ 1.04 Anti-dilutive shares 1.0 2.7 1.2 2.7

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments Except for the items below, there have been no material changes to the Company's commitments compared to the commitments described in Note 16, Commitments and Contingencies , in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K. Clock-Signal, Supplier Component Remediation Liability As of September 30, 2017 and December 31, 2016, the Company had approximately $0.8 million and $10.8 million , respectively, in other accrued liabilities on the Condensed Consolidated Balance Sheets for the expected remediation costs for certain products containing a defect in a clock-signal component manufactured by a third-party supplier. The Company has been advised by the component supplier that components may begin to fail after the product has been in operation for 18 months. The Company is in the process of implementing the remediation with its customers. Guarantees The Company enters into agreements with customers that contain indemnification provisions relating to potential situations where claims could be alleged that the Company’s products solely, or in combination with other third party products, infringe the intellectual property rights of a third-party. As of September 30, 2017 and December 31, 2016, the Company recorded $20.1 million and $28.9 million , respectively, for such indemnification obligations in other accrued liabilities and other long-term liabilities on the Condensed Consolidated Balance Sheets. During the nine months ended September 30, 2017 , $15.0 million of indemnification obligations expired and were therefore released. Legal Proceedings Investigations The U.S. Securities and Exchange Commission ("SEC") and the U.S. Department of Justice ("DOJ") are conducting investigations into possible violations by the Company of the U.S. Foreign Corrupt Practices Act ("FCPA"). The Company is cooperating with these agencies regarding these matters. The Company’s Audit Committee, with the assistance of independent advisors, has been investigating and conducting a thorough review of possible violations of the FCPA, and has made recommendations for remedial measures, including employee disciplinary actions in foreign jurisdictions, which the Company has implemented and continues to implement. The Company is unable to predict the duration, scope or outcome of the SEC and DOJ investigations, but believes that an adverse outcome is reasonably possible. However, the Company is not able to estimate a reasonable range of possible loss. The SEC and/or DOJ could take action against the Company or the Company could agree to settle. In such event, the Company could be required to pay substantial fines and sanctions and/or implement additional remedial measures; in addition, it may be determined that the Company violated the FCPA. Other Litigations and Investigations In addition to the investigations discussed above, the Company is involved in other investigations, disputes, litigations, and legal proceedings. The Company records an accrual for loss contingencies for legal proceedings when it believes that an unfavorable outcome is both (a) probable and (b) the amount or range of any possible loss is reasonably estimable. The Company intends to aggressively defend itself in these matters, and while there can be no assurances and the outcome of these matters is currently not determinable, the Company currently believes that none of these existing claims or proceedings are likely to have a material adverse effect on its financial position. Notwithstanding the foregoing, there are many uncertainties associated with any litigation and these matters or other third-party claims against the Company may cause the Company to incur costly litigation and/or substantial settlement charges. In addition, the resolution of any intellectual property litigation may require the Company to make royalty payments, which could adversely affect gross margins in future periods. If any of those events were to occur, the Company's business, financial condition, results of operations, and cash flows could be adversely affected. The actual liability in any such matters may be materially different from the Company's estimates, if any, which could result in the need to adjust the liability and record additional expenses.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Restructuring Activities Subsequent to September 30, 2017 , the Company amended the 2017 Restructuring Plan to further realign its workforce. The Company expects to record severance charges of approximately $23.0 million to $27.0 million related to headcount reductions in the fourth quarter of 2017. Dividend Declaration On October 24, 2017, the Company announced that it had declared a cash dividend of $0.10 per share of common stock payable on December 22, 2017 to stockholders of record as of the close of business on December 1, 2017. Stock Repurchase Activities Subsequent to September 30, 2017 , through the filing of this Report, the Company repurchased 4.0 million shares of its common stock, for an aggregate purchase price of $100.0 million at an average price of $24.80 per share, under the Stock Repurchase Program. Repurchases of approximately 3.6 million shares were settled prior to the filing of this Report and the remaining shares will be settled after the filing date. The Company has an aggregate of $229.7 million of authorized funds remaining under the Stock Repurchase Program, as of the filing date.

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited Condensed Consolidated Financial Statements of Juniper Networks, Inc. (the “Company” or “Juniper”) have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The Condensed Consolidated Balance Sheet as of December 31, 2016 , has been derived from the audited Consolidated Financial Statements at that date. In the opinion of management, all adjustments, including normal recurring accruals, considered necessary for a fair presentation have been included. The results of operations for the three and nine months ended September 30, 2017 , are not necessarily indicative of the results that may be expected for the year ending December 31, 2017 , or any future period. The information included in this Quarterly Report on Form 10-Q (“Report”) should be read in conjunction with “Management's Discussion and Analysis of Financial Condition and Results of Operations,” “Risk Factors,” “Quantitative and Qualitative Disclosures About Market Risk,” and the Consolidated Financial Statements and footnotes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2016 (the "Form 10-K"). Excess tax benefits from share-based compensation in prior periods have been reclassified to conform to the current-period presentation in the Condensed Consolidated Statements of Cash Flows upon adoption of the accounting standard described in Note 2, Summary of Significant Accounting Policies . In addition, certain other amounts in the Condensed Consolidated Statements of Cash Flows have been reclassified to conform to the current-period presentation. The preparation of the financial statements and related disclosures in accordance with U.S. GAAP requires the Company to make judgments, assumptions, and estimates that affect the amounts reported in the Condensed Consolidated Financial Statements and the accompanying notes. Actual results could differ materially from those estimates under different assumptions or conditions.
Recent accounting pronouncements	Recently Adopted Accounting Standard On January 1, 2017, the Company adopted Financial Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") No. 2016-09 (Topic 718) Compensation—Stock Compensation: Improvements to Employee Share-Based Payment Accounting , which simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, forfeiture, statutory tax withholding requirements, and classification on the statement of cash flows. The impact of the adoption on the Company's Condensed Consolidated Financial Statements was as follows: • Forfeitures: The Company elected to account for forfeitures as they occur using a modified retrospective transition method, rather than estimating forfeitures, resulting in a cumulative-effect adjustment of $9.0 million , which increased the January 1, 2017 opening accumulated deficit balance on the Condensed Consolidated Balance Sheets. • Income tax accounting: The Company is also required to record excess tax benefits and tax deficiencies related to stock- based compensation as income tax benefit or expense in the statement of operations prospectively when share-based awards vest or are settled. Upon adoption, the Company recognized the previously unrecognized excess tax benefits using the modified retrospective transition method, which resulted in no impact to the January 1, 2017 opening accumulated deficit balance as previously unrecognized excess tax effects were fully offset by a valuation allowance. • Cash flow presentation of excess tax benefits: The Company is required to classify excess tax benefits along with other income tax cash flows as an operating activity either prospectively or retrospectively. The Company elected to apply the change in presentation to the statements of cash flows retrospectively and no longer classify the excess tax benefits from share-based compensation as a financing activity. For the nine months ended September 30, 2016, the Company reclassified $5.8 million of excess tax benefits from share-based compensation to operating activities from financing activities. Recent Accounting Standards Not Yet Effective In August 2017, the FASB issued ASU No. 2017-12 (Topic 815) Derivatives and Hedging — Targeted Improvements to Accounting for Hedging Activities, which expands an entity's ability to hedge financial and nonfinancial risk components and amends how companies assess effectiveness as well as changes the presentation and disclosure requirements. The new standard is to be applied on a modified retrospective basis and is effective for interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the impact of adoption on the Consolidated Financial Statements. In May 2017, the FASB issued ASU No. 2017-09 (Topic 718) Compensation—Stock Compensation: Scope of Modification Accounting, which provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting. The new standard is effective on a prospective basis for interim and annual periods beginning after December 15, 2017, with early adoption permitted. In March 2017, the FASB issued ASU No. 2017-08 Receivables—Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities which shortens the amortization period for the premium on certain purchased callable debt securities to the earliest call date. The ASU will not impact debt securities held at a discount. This standard is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within those annual reporting periods, and is to be applied on a modified retrospective basis with early adoption permitted. The Company is currently evaluating the impact of adoption on the Consolidated Financial Statements. In February 2017, the FASB issued ASU No. 2017-05 Other Income—Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets, which amends guidance on how entities account for the derecognition of a nonfinancial asset or an in substance nonfinancial asset that is not a business. This standard is effective for annual reporting periods beginning after December 15, 2017, including interim reporting periods within those annual reporting periods, and is to be applied on either a retrospective or modified retrospective basis with early adoption permitted. The adoption of this standard will not have a material impact on the Consolidated Financial Statements. In January 2017, the FASB issued ASU No. 2017-04 (Topic 350) Intangibles—Goodwill and Other: Simplifying the Test for Goodwill Impairmen t, which removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. Under the amended guidance, a goodwill impairment charge will now be recognized for the amount by which the carrying value of a reporting unit exceeds its fair value, not to exceed the carrying amount of goodwill. This ASU will be applied on a prospective basis and is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted for any impairment tests performed after January 1, 2017. In January 2017, the FASB issued ASU No. 2017-01 (Topic 805) Business Combinations: Clarifying the Definition of a Business , which clarifies the definition of a business and assists entities with evaluating when a set of transferred assets and activities is a business. This ASU is effective for interim and annual periods beginning after December 15, 2017, with early adoption permitted and will be applied on a prospective basis. In November 2016, the FASB issued ASU No. 2016-18 (Topic 230) Statement of Cash Flow: Restricted Cash, which provides guidance on the classification of restricted cash to be included with cash and cash equivalents when reconciling the beginning of period and end of period total amounts on the statement of cash flows. The amendments of this ASU are effective for interim and annual periods beginning after December 15, 2017, with early adoption permitted. The standard must be applied retrospectively to all periods presented. The adoption of this standard will not have a material impact on the cash flow activity presented on the Company's Consolidated Statements of Cash Flows. In October 2016, the FASB issued ASU No. 2016-16 (Topic 740) Income Taxes: Intra-Entity Transfers of Assets Other Than Inventory, which requires the recognition of the income tax consequences of an intra-entity transfer of an asset, other than inventory, when the transfer occurs. This ASU will be effective for annual and interim reporting periods beginning after December 15, 2017 and is to be applied on a modified retrospective basis. Early adoption is permitted. The adoption of this standard will not have a material impact on the Consolidated Financial Statements. In August 2016, the FASB issued ASU No. 2016-15 (Topic 230) Statement of Cash Flow: Classification of Certain Cash Receipts and Cash Payments, which clarifies how companies present and classify certain cash receipts and cash payments in the statement of cash flows. This pronouncement is effective for interim and annual reporting periods beginning after December 15, 2017 and will be applied on a retrospective basis. Early adoption is permitted. The adoption of this standard will not have a material impact on the Company's Consolidated Statements of Cash Flows. In June 2016, the FASB issued ASU No. 2016-13 (Topic 326) Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments , which provides more decision-useful information about the expected credit losses on financial instruments and changes the loss impairment methodology. This pronouncement is effective for reporting periods beginning after December 15, 2019, and interim periods within those fiscal years, using a modified retrospective adoption method. Early adoption is permitted. The Company is currently evaluating the impact that this standard will have on its Consolidated Financial Statements and disclosures. In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases , which requires recognition of lease assets and lease liabilities on the balance sheet by lessees for leases classified as operating leases with a lease term of more than twelve months. This ASU should be applied on a modified retrospective basis and is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact of adoption of this standard and has commenced the assessment phase to determine the approach for implementing this standard. The adoption of this standard is expected to have a material impact on the Company's Consolidated Balance Sheets and disclosures. The Company is still evaluating the impact this standard will have on the Consolidated Statements of Operations. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments—Overall: Recognition and Measurement of Financial Assets and Financial Liabilities , which changes how entities measure equity investments and present changes in the fair value of financial liabilities measured under the fair value option. The guidance also updates certain presentation and disclosure requirements. This ASU is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. This ASU is to be applied on a prospective basis for amendments related to equity securities without readily determinable fair values, and all other amendments in this standard will be applied on a modified retrospective basis. For equity securities without readily determinable fair values, we expect to elect the measurement alternative, defined as cost, less impairments, adjusted by observable price changes. The Company does not anticipate that the adoption of the amendments that will be applied on a modified retrospective basis will have a material impact on the Consolidated Financial Statements. In May 2014, the FASB issued ASU No. 2014-09 (Topic 606) —Revenue from Contracts with Customers and several amendments thereafter (“ASU 2014-09”), which provides guidance for revenue recognition that will supersede the revenue recognition requirements in Topic 605, and most industry specific guidance. The core principle for ASU 2014-09 is that revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2017. The Company intends to adopt ASU 2014-09 on January 1, 2018 retrospectively, applying the amendments to each prior reporting period presented and currently remains on schedule with its implementation and the preparation of its prior-period financial statements . Upon adoption, the Company expects a material impact to the opening balance sheet as of January 1, 2016 related to the cumulative effect of adopting this standard, primarily due to the application of the new guidance in the areas of distributor sales, software revenue, contract acquisition costs, variable consideration, and revenue allocation. The Company continues to assess the impact of ASU 2014-09 including any changes to systems, processes, and the control environment as it works through the adoption in 2017, and there remain areas still to be fully concluded upon. In addition, there are ongoing interpretive reviews, which may alter the Company's conclusions on key accounting assessments and the financial impact of ASU 2014-09 on the Company's Consolidated Financial Statements. For further information, refer to Note 2, Significant Accounting Policies , in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K.

Business Combinations (Tables)

Business Combinations (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the estimated fair value of the assets acquired at the acquisition date (in millions, except years): Amount Net tangible assets $ 1.4 Existing technology intangible asset (*) 15.4 Goodwill 16.7 Total $ 33.5 ________________________________ (*) Weighted average estimated useful life of 5 years .

Cash Equivalents and Investme27

Cash Equivalents and Investments (Tables)	9 Months Ended
	Sep. 30, 2017
Cash Equivalents and Investments [Abstract]
Unrealized gains and losses and fair value of available-for-sale and trading securities	The following table summarizes the Company's unrealized gains and losses and fair value of investments designated as available-for-sale and trading securities as of September 30, 2017 and December 31, 2016 (in millions): As of September 30, 2017 As of December 31, 2016 Amortized Gross Unrealized Gross Unrealized Estimated Fair Amortized Gross Unrealized Gross Unrealized Estimated Fair Fixed income securities: Asset-backed securities $ 288.1 $ — $ (0.3 ) $ 287.8 $ 303.0 $ 0.2 $ (0.2 ) $ 303.0 Certificates of deposit 50.0 — — 50.0 66.1 — — 66.1 Commercial paper 124.0 — — 124.0 147.7 — — 147.7 Corporate debt securities 834.1 0.8 (0.8 ) 834.1 846.5 0.4 (2.0 ) 844.9 Foreign government debt securities 64.8 — (0.1 ) 64.7 34.0 — (0.1 ) 33.9 Time deposits 411.4 — — 411.4 264.6 — — 264.6 U.S. government agency securities 156.9 — (0.4 ) 156.5 127.0 — (0.3 ) 126.7 U.S. government securities 548.3 0.1 (0.4 ) 548.0 390.7 0.1 (0.4 ) 390.4 Total fixed income securities 2,477.6 0.9 (2.0 ) 2,476.5 2,179.6 0.7 (3.0 ) 2,177.3 Money market funds 990.7 — — 990.7 592.2 — — 592.2 Mutual funds 8.2 — — 8.2 8.0 — — 8.0 Publicly-traded equity securities — — — — 5.3 — (0.7 ) 4.6 Total available-for-sale securities 3,476.5 0.9 (2.0 ) 3,475.4 2,785.1 0.7 (3.7 ) 2,782.1 Trading securities in mutual funds 26.1 — — 26.1 21.0 — — 21.0 Total $ 3,502.6 $ 0.9 $ (2.0 ) $ 3,501.5 $ 2,806.1 $ 0.7 $ (3.7 ) $ 2,803.1 Reported as: Cash equivalents $ 1,588.8 $ — $ — $ 1,588.8 $ 907.1 $ — $ — $ 907.1 Restricted investments 77.1 — — 77.1 71.9 — — 71.9 Short-term investments 922.3 0.1 (0.4 ) 922.0 753.4 0.1 (1.2 ) 752.3 Long-term investments 914.4 0.8 (1.6 ) 913.6 1,073.7 0.6 (2.5 ) 1,071.8 Total $ 3,502.6 $ 0.9 $ (2.0 ) $ 3,501.5 $ 2,806.1 $ 0.7 $ (3.7 ) $ 2,803.1
Maturities of fixed income securities	The following table presents the contractual maturities of the Company's total fixed income securities as of September 30, 2017 (in millions): Amortized Cost Estimated Fair Value Due in less than one year $ 1,563.2 $ 1,562.9 Due between one and five years 914.4 913.6 Total $ 2,477.6 $ 2,476.5
Available-for-sale securities in unrealized loss position	The following tables present the Company's available-for-sale securities that were in an unrealized loss position as of September 30, 2017 and December 31, 2016 (in millions): As of September 30, 2017 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Fixed income securities: Asset-backed securities $ 224.2 $ (0.3 ) $ — $ — $ 224.2 $ (0.3 ) Corporate debt securities 361.6 (0.5 ) 59.5 (0.3 ) 421.1 (0.8 ) Foreign government debt securities 36.6 (0.1 ) — — 36.6 (0.1 ) U.S. government agency securities 89.0 (0.2 ) 18.0 (0.2 ) 107.0 (0.4 ) U.S. government securities 256.3 (0.4 ) 1.8 — 258.1 (0.4 ) Total available-for-sale securities $ 967.7 $ (1.5 ) $ 79.3 $ (0.5 ) $ 1,047.0 $ (2.0 ) As of December 31, 2016 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Fixed income securities: Asset-backed securities $ 122.2 $ (0.2 ) $ — $ — $ 122.2 $ (0.2 ) Corporate debt securities 470.8 (1.9 ) 76.7 (0.1 ) 547.5 (2.0 ) Foreign government debt securities 20.3 (0.1 ) — — 20.3 (0.1 ) U.S. government agency securities 106.7 (0.3 ) — — 106.7 (0.3 ) U.S. government securities 254.1 (0.4 ) — — 254.1 (0.4 ) Total fixed income securities 974.1 (2.9 ) 76.7 (0.1 ) 1,050.8 (3.0 ) Publicly-traded equity securities 4.6 (0.7 ) — — 4.6 (0.7 ) Total available-for-sale securities $ 978.7 $ (3.6 ) $ 76.7 $ (0.1 ) $ 1,055.4 $ (3.7 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Assets and liabilities measured at fair value on a recurring basis	The following table provides a summary of assets and liabilities measured at fair value on a recurring basis and as reported in the Condensed Consolidated Balance Sheets (in millions): Fair Value Measurements at Fair Value Measurements at Quoted Prices in Significant Other Significant Other Total Quoted Prices in Significant Other Significant Other Total Assets: Available-for-sale securities: Asset-backed securities $ — $ 287.8 $ — $ 287.8 $ — $ 303.0 $ — $ 303.0 Certificates of deposit — 50.0 — 50.0 — 66.1 — 66.1 Commercial paper — 124.0 — 124.0 — 147.7 — 147.7 Corporate debt securities — 834.1 — 834.1 — 844.9 — 844.9 Foreign government debt securities — 64.7 — 64.7 — 33.9 — 33.9 Money market funds 990.7 — — 990.7 592.2 — — 592.2 Mutual funds 8.2 — — 8.2 8.0 — — 8.0 Publicly-traded equity securities — — — — 4.6 — — 4.6 Time deposits — 411.4 — 411.4 — 264.6 — 264.6 U.S. government agency securities — 156.5 — 156.5 — 126.7 — 126.7 U.S. government securities 343.7 204.3 — 548.0 345.0 45.4 — 390.4 Total available-for-sale securities 1,342.6 2,132.8 — 3,475.4 949.8 1,832.3 — 2,782.1 Trading securities in mutual funds 26.1 — — 26.1 21.0 — — 21.0 Privately-held debt and redeemable preferred stock securities — — 42.3 42.3 — — 43.7 43.7 Derivative assets: Foreign exchange contracts — 8.5 — 8.5 — 0.9 — 0.9 Total assets measured at fair value $ 1,368.7 $ 2,141.3 $ 42.3 $ 3,552.3 $ 970.8 $ 1,833.2 $ 43.7 $ 2,847.7 Liabilities: Derivative liabilities: Foreign exchange contracts $ — $ (0.6 ) $ — $ (0.6 ) $ — $ (4.9 ) $ — $ (4.9 ) Total liabilities measured at fair value $ — $ (0.6 ) $ — $ (0.6 ) $ — $ (4.9 ) $ — $ (4.9 ) Total assets, reported as: Cash equivalents $ 947.9 $ 640.9 $ — $ 1,588.8 $ 549.4 $ 357.7 $ — $ 907.1 Restricted investments 77.1 — — 77.1 71.9 — — 71.9 Short-term investments 231.9 690.1 — 922.0 178.0 574.3 — 752.3 Long-term investments 111.8 801.8 — 913.6 171.5 900.3 — 1,071.8 Prepaid expenses and other current assets — 8.5 — 8.5 — 0.9 — 0.9 Other long-term assets — — 42.3 42.3 — — 43.7 43.7 Total assets measured at fair value $ 1,368.7 $ 2,141.3 $ 42.3 $ 3,552.3 $ 970.8 $ 1,833.2 $ 43.7 $ 2,847.7 Total liabilities, reported as: Other accrued liabilities $ — $ (0.6 ) $ — $ (0.6 ) $ — $ (4.9 ) $ — $ (4.9 ) Total liabilities measured at fair value $ — $ (0.6 ) $ — $ (0.6 ) $ — $ (4.9 ) $ — $ (4.9 )

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative instruments	The notional amount of the Company's foreign currency derivatives are summarized as follows (in millions): As of September 30, December 31, Cash flow hedges $ 231.6 $ 172.0 Non-designated derivatives 147.1 — Total $ 378.7 $ 172.0

Goodwill and Purchased Intang30

Goodwill and Purchased Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	The following table presents goodwill activity (in millions): Balance as of December 31, 2016 $ 3,081.7 Additions due to business combination 16.7 Other (*) (2.2 ) Balance as of September 30, 2017 $ 3,096.2 ________________________________ (*) Other primarily consists of certain purchase accounting adjustments related to previously completed business combinations.

Other Financial Information (Ta

Other Financial Information (Tables)	9 Months Ended
	Sep. 30, 2017
Other Financial Information [Abstract]
Inventories	Total inventory consisted of the following (in millions): As of September 30, December 31, Production and service materials $ 72.6 $ 75.6 Finished goods 18.3 19.9 Inventory $ 90.9 $ 95.5 Reported as: Prepaid expenses and other current assets $ 84.9 $ 91.4 Other long-term assets 6.0 4.1 Total $ 90.9 $ 95.5
Warranties	Changes during the nine months ended September 30, 2017 in the Company’s warranty reserve as reported within other accrued liabilities in the Condensed Consolidated Balance Sheets were as follows (in millions): Balance as of December 31, 2016 $ 41.3 Provisions made during the period 29.6 Actual costs incurred during the period (41.5 ) Balance as of September 30, 2017 $ 29.4
Deferred revenue	Details of the Company's deferred revenue, as reported in the Condensed Consolidated Balance Sheets, were as follows (in millions): As of September 30, December 31, Deferred product revenue: Undelivered product commitments and other product deferrals $ 309.3 $ 302.4 Distributor inventory and other sell-through items 61.9 74.2 Deferred gross product revenue 371.2 376.6 Deferred cost of product revenue (47.5 ) (53.7 ) Deferred product revenue, net 323.7 322.9 Deferred service revenue 1,139.2 1,158.2 Total $ 1,462.9 $ 1,481.1 Reported as: Current $ 977.4 $ 1,032.0 Long-term 485.5 449.1 Total $ 1,462.9 $ 1,481.1
Other expense, net	Other expense, net, consisted of the following (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Interest income $ 14.7 $ 9.1 $ 37.1 $ 25.5 Interest expense (25.3 ) (25.1 ) (75.6 ) (72.6 ) Gain on investments, net 4.7 1.9 6.7 0.1 Other 0.8 0.7 (2.0 ) (0.2 ) Other expense, net $ (5.1 ) $ (13.4 ) $ (33.8 ) $ (47.2 )

Restructuring Charges (Tables)

Restructuring Charges (Tables)	9 Months Ended
	Sep. 30, 2017
Restructuring and Related Activities [Abstract]
Schedule of restructuring liabilities	Restructuring liabilities are reported within other accrued liabilities in the Condensed Consolidated Balance Sheets. The following table provides a summary of changes in the restructuring liabilities primarily related to the 2017 Restructuring Plan initiated in February 2017 (in millions): December 31, 2016 (*) Charges Cash Payments Other September 30, Severance $ 0.7 $ 26.0 $ (25.5 ) $ (0.1 ) $ 1.1 Contract terminations and other 0.5 3.4 (0.4 ) 0.1 3.6 Total $ 1.2 $ 29.4 $ (25.9 ) $ — $ 4.7 ________________________________ (*) Consists of costs in connection with a prior restructuring plan that is substantially complete.

Debt and Financing (Tables)

Debt and Financing (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Instruments [Abstract]
Long-term debt	The Company's long-term debt is summarized as follows (in millions, except percentages): As of September 30, 2017 Amount Effective Interest Rates Senior Notes ("Notes"): 3.125% fixed-rate notes, due February 2019 $ 350.0 3.36 % 3.300% fixed-rate notes, due June 2020 300.0 3.47 % 4.600% fixed-rate notes, due March 2021 300.0 4.69 % 4.500% fixed-rate notes, due March 2024, issued March 2014 350.0 4.63 % 4.500% fixed-rate notes, due March 2024, issued February 2016 150.0 4.87 % 4.350% fixed-rate notes, due June 2025 300.0 4.47 % 5.950% fixed-rate notes, due March 2041 400.0 6.03 % Total senior notes 2,150.0 Unaccreted discount and debt issuance costs (14.3 ) Total $ 2,135.7

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Schedule of Repurchase Agreements	The following table summarizes the Company's repurchases and retirements of its common stock under its Stock Repurchase Program (in millions, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Shares repurchased 5.0 4.9 13.5 13.5 Average price per share $ 28.16 $ 23.04 $ 28.85 $ 23.25 Amount repurchased $ 140.0 $ 112.4 $ 390.0 $ 312.9
Components of accumulated other comprehensive income, net of taxes	The components of accumulated other comprehensive loss, net of related taxes, for the nine months ended September 30, 2017 were as follows (in millions): Unrealized Gains (Losses) on Available-for- Sale Securities (1) Unrealized (Losses) Gains on Cash Flow Hedges (2) Foreign Currency Translation Adjustments Total Balance as of December 31, 2016 $ 16.6 $ (4.5 ) $ (49.4 ) $ (37.3 ) Other comprehensive gains before reclassifications 1.4 14.6 19.3 35.3 Amount reclassified from accumulated other comprehensive loss (2.0 ) (2.4 ) — (4.4 ) Other comprehensive (loss) gains, net (0.6 ) 12.2 19.3 30.9 Balance as of September 30, 2017 $ 16.0 $ 7.7 $ (30.1 ) $ (6.4 ) ________________________________ (1) The reclassifications out of accumulated other comprehensive loss during the nine months ended September 30, 2017 for realized gains on available-for-sale securities were not material, and were included in other expense, net, in the Condensed Consolidated Statements of Operations. (2) The reclassifications out of accumulated other comprehensive loss during the nine months ended September 30, 2017 for realized gains on cash flow hedges were not material, and were included within cost of revenues, research and development, sales and marketing, and general and administrative in the Condensed Consolidated Statements of Operations.

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of share-based compensation, stock options, activity	The following table summarizes the Company’s stock option activity and related information as of and for the nine months ended September 30, 2017 (in millions, except for per share amounts and years): Outstanding Options Number of Shares Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance as of December 31, 2016 2.4 $ 29.20 Exercised (0.5 ) 14.97 Expired/Canceled (0.8 ) 31.09 Balance as of September 30, 2017 1.1 $ 34.31 1.1 $ 3.1 As of September 30, 2017: Vested and expected-to-vest options 1.1 $ 34.31 1.1 $ 3.1 Exercisable options 1.0 $ 35.56 0.8 $ 2.1
Schedule of nonvested share activity	The Company’s RSU, restricted stock award ("RSA"), and PSA activity and related information as of and for the nine months ended September 30, 2017 were as follows (in millions, except per share amounts and years): Outstanding RSUs, RSAs, and PSAs Number of Shares Weighted Average Grant-Date Fair Value per Share Weighted Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance as of December 31, 2016 20.9 $ 24.05 RSUs granted (1)(3) 6.6 27.56 RSUs assumed in acquisitions 0.1 26.91 PSAs granted (2)(3) 0.6 27.37 RSUs vested (6.0 ) 23.81 RSAs vested (0.4 ) 22.80 PSAs vested (0.5 ) 24.29 RSUs canceled (1.5 ) 24.57 PSAs canceled (0.5 ) 25.11 Balance as of September 30, 2017 19.3 $ 25.23 1.1 $ 537.1 ________________________________ (1) Includes service-based and market-based RSUs. (2) The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee of the Board are achieved at target is 0.4 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 0.6 million shares. (3) The grant date fair value of RSUs and PSAs were reduced by the present value of dividends expected to be paid on the underlying shares of common stock during the requisite and derived service period as these awards are not entitled to receive dividends until vested. During the nine months ended September 30, 2017 , the Company declared a quarterly cash dividend of $0.10 per share of common stock on January 26, 2017, April 25, 2017, and July 25, 2017.
Schedule of employee service share-based compensation, allocation of recognized period costs	Share-based compensation expense associated with stock options, RSUs, RSAs, PSAs, and ESPP was recorded in the following cost and expense categories in the Condensed Consolidated Statements of Operations (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cost of revenues - Product $ 1.5 $ 1.5 $ 3.8 $ 4.9 Cost of revenues - Service 3.9 3.5 13.5 11.3 Research and development 18.5 27.2 67.4 89.0 Sales and marketing 13.7 17.5 45.3 40.7 General and administrative 7.4 5.9 21.1 17.1 Total $ 45.0 $ 55.6 $ 151.1 $ 163.0
Disclosure of share-based compensation arrangements by share-based payment award	The following table summarizes share-based compensation expense by award type (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Stock options $ 0.2 $ 1.5 $ 0.5 $ 3.7 RSUs, RSAs, and PSAs 41.0 50.3 138.9 147.6 ESPP 3.8 3.8 11.7 11.7 Total $ 45.0 $ 55.6 $ 151.1 $ 163.0

Segments (Tables)

Segments (Tables)	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Financial information for each segment	The following table presents net revenues by customer vertical (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cloud $ 344.9 $ 359.4 $ 1,056.1 $ 911.5 Telecom/Cable 576.9 599.4 1,707.8 1,688.5 Strategic Enterprise 336.0 326.5 1,023.8 1,004.5 Total $ 1,257.8 $ 1,285.3 $ 3,787.7 $ 3,604.5 The following table presents net revenues by product and service (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Routing $ 585.8 $ 620.2 $ 1,679.9 $ 1,699.0 Switching 212.6 222.5 730.2 607.2 Security 71.3 85.5 205.7 237.1 Total product 869.7 928.2 2,615.8 2,543.3 Total service 388.1 357.1 1,171.9 1,061.2 Total $ 1,257.8 $ 1,285.3 $ 3,787.7 $ 3,604.5
Net revenues by geographic region	The Company attributes revenues to geographic region based on the customer’s shipping address. The following table presents net revenues by geographic region (in millions): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Americas: United States $ 668.8 $ 684.6 $ 2,076.0 $ 1,924.9 Other 60.4 60.4 165.6 168.3 Total Americas 729.2 745.0 2,241.6 2,093.2 Europe, Middle East, and Africa 298.6 338.0 871.3 923.5 Asia Pacific 230.0 202.3 674.8 587.8 Total $ 1,257.8 $ 1,285.3 $ 3,787.7 $ 3,604.5

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Schedule of effective income tax rate reconciliation	The following table provides details of income taxes (in millions, except percentages): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Income before income taxes $ 225.8 $ 236.6 $ 611.6 $ 555.3 Income tax provision $ 60.1 $ 64.2 $ 157.3 $ 151.5 Effective tax rate 26.6 % 27.1 % 25.7 % 27.3 %

Net Income Per Share (Tables)

Net Income Per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Schedule of earnings per share, basic and diluted	The Company computed basic and diluted net income per share as follows (in millions, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Numerator: Net income $ 165.7 $ 172.4 $ 454.3 $ 403.8 Denominator: Weighted-average shares used to compute basic net income per share 378.3 381.0 380.0 382.3 Dilutive effect of employee stock awards 4.4 3.5 6.5 5.6 Weighted-average shares used to compute diluted net income per share 382.7 384.5 386.5 387.9 Net income per share Basic $ 0.44 $ 0.45 $ 1.20 $ 1.06 Diluted $ 0.43 $ 0.45 $ 1.18 $ 1.04 Anti-dilutive shares 1.0 2.7 1.2 2.7

Summary of Significant Accoun39

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities	$ 1,045.9	$ 776.3
Net cash used in financing activities	$ (444.6)	(200.1)
Accounting Standards Update 2016-09, Excess Tax Benefit Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities		5.8
Net cash used in financing activities		$ (5.8)
Accounting Standards Update 2016-09, Excess Tax Benefit Component | Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment			$ 9

Business Combinations - Narrati

Business Combinations - Narrative (Details) - Cyphort $ in Millions	Sep. 18, 2017USD ($)
Business Acquisition [Line Items]
Voting interests acquired (percentage)	100.00%
Fair value of grants acquired	$ 3.8
Payments to acquire businesses	$ 33.5

Business Combinations - Purchas

Business Combinations - Purchase Price Allocation (Details) - Cyphort $ in Millions	Sep. 18, 2017USD ($)
Business Acquisition [Line Items]
Net tangible assets	$ 1.4
Existing technology intangible asset()	15.4
Goodwill, Gross	16.7
Total	$ 33.5
Weighted Average Estimated Useful Life (in Years)	5 years

Cash Equivalents and Investme42

Cash Equivalents and Investments - Available-For-Sale and Trading Securities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Available-for-sale securities:
Available-for-sale securities, amortized cost	$ 3,476.5	$ 2,785.1
Available-for-sale securities, gross unrealized gains	0.9	0.7
Available-for-sale securities, gross unrealized losses	(2)	(3.7)
Available-for-sale securities, estimated fair value	3,475.4	2,782.1
Available-for-sale and Trading Securities [Abstract]
Total investments, amortized cost	3,502.6	2,806.1
Total investments, gross unrealized gains	0.9	0.7
Total investments, gross unrealized losses	(2)	(3.7)
Total investments, estimated fair value	3,501.5	2,803.1
Debt Securities
Available-for-sale securities:
Available-for-sale securities, amortized cost	2,477.6	2,179.6
Available-for-sale securities, gross unrealized gains	0.9	0.7
Available-for-sale securities, gross unrealized losses	(2)	(3)
Available-for-sale securities, estimated fair value	2,476.5	2,177.3
Asset-backed securities
Available-for-sale securities:
Available-for-sale securities, amortized cost	288.1	303
Available-for-sale securities, gross unrealized gains	0	0.2
Available-for-sale securities, gross unrealized losses	(0.3)	(0.2)
Available-for-sale securities, estimated fair value	287.8	303
Certificates of deposit
Available-for-sale securities:
Available-for-sale securities, amortized cost	50	66.1
Available-for-sale securities, gross unrealized gains	0	0
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale securities, estimated fair value	50	66.1
Commercial paper
Available-for-sale securities:
Available-for-sale securities, amortized cost	124	147.7
Available-for-sale securities, gross unrealized gains	0	0
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale securities, estimated fair value	124	147.7
Corporate debt securities
Available-for-sale securities:
Available-for-sale securities, amortized cost	834.1	846.5
Available-for-sale securities, gross unrealized gains	0.8	0.4
Available-for-sale securities, gross unrealized losses	(0.8)	(2)
Available-for-sale securities, estimated fair value	834.1	844.9
Foreign government debt securities
Available-for-sale securities:
Available-for-sale securities, amortized cost	64.8	34
Available-for-sale securities, gross unrealized gains	0	0
Available-for-sale securities, gross unrealized losses	(0.1)	(0.1)
Available-for-sale securities, estimated fair value	64.7	33.9
Time deposits
Available-for-sale securities:
Available-for-sale securities, amortized cost	411.4	264.6
Available-for-sale securities, gross unrealized gains	0	0
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale securities, estimated fair value	411.4	264.6
U.S. government agency securities
Available-for-sale securities:
Available-for-sale securities, amortized cost	156.9	127
Available-for-sale securities, gross unrealized gains	0	0
Available-for-sale securities, gross unrealized losses	(0.4)	(0.3)
Available-for-sale securities, estimated fair value	156.5	126.7
U.S. government securities
Available-for-sale securities:
Available-for-sale securities, amortized cost	548.3	390.7
Available-for-sale securities, gross unrealized gains	0.1	0.1
Available-for-sale securities, gross unrealized losses	(0.4)	(0.4)
Available-for-sale securities, estimated fair value	548	390.4
Mutual funds
Available-for-sale securities:
Available-for-sale securities, amortized cost	8.2	8
Available-for-sale securities, gross unrealized gains	0	0
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale securities, estimated fair value	8.2	8
Trading securities:
Trading securities, amortized cost	26.1	21
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Trading securities, estimated fair value	26.1	21
Money market funds
Available-for-sale securities:
Available-for-sale securities, amortized cost	990.7	592.2
Available-for-sale securities, gross unrealized gains	0	0
Available-for-sale securities, gross unrealized losses	0	0
Available-for-sale securities, estimated fair value	990.7	592.2
Publicly-traded equity securities
Available-for-sale securities:
Available-for-sale securities, amortized cost	0	5.3
Available-for-sale securities, gross unrealized gains	0	0
Available-for-sale securities, gross unrealized losses	0	(0.7)
Available-for-sale securities, estimated fair value	0	4.6
Cash equivalents
Available-for-sale and Trading Securities [Abstract]
Total investments, amortized cost	1,588.8	907.1
Total investments, gross unrealized gains	0	0
Total investments, gross unrealized losses	0	0
Total investments, estimated fair value	1,588.8	907.1
Restricted investments
Available-for-sale and Trading Securities [Abstract]
Total investments, amortized cost	77.1	71.9
Total investments, gross unrealized gains	0	0
Total investments, gross unrealized losses	0	0
Total investments, estimated fair value	77.1	71.9
Short-term investments
Available-for-sale and Trading Securities [Abstract]
Total investments, amortized cost	922.3	753.4
Total investments, gross unrealized gains	0.1	0.1
Total investments, gross unrealized losses	(0.4)	(1.2)
Total investments, estimated fair value	922	752.3
Long-term investments
Available-for-sale and Trading Securities [Abstract]
Total investments, amortized cost	914.4	1,073.7
Total investments, gross unrealized gains	0.8	0.6
Total investments, gross unrealized losses	(1.6)	(2.5)
Total investments, estimated fair value	$ 913.6	$ 1,071.8

Cash Equivalents and Investme43

Cash Equivalents and Investments - Maturities of Fixed Income Investments (Details) $ in Millions	Sep. 30, 2017USD ($)
Schedule of Fixed Income Securities Maturities [Abstract]
Amortized cost due within one year	$ 1,563.2
Amortized cost due between one and five years	914.4
Total investments, amortized cost	2,477.6
Estimated fair value due within one year	1,562.9
Estimated fair value due between one and five year	913.6
Total investments, estimated fair value	$ 2,476.5

Cash Equivalents and Investme44

Cash Equivalents and Investments - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)Investment	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)Investment	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)Investment
Cash Equivalents and Investments [Abstract]
Total investments in unrealized loss position | Investment	582		582		494
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	$ 123.2		$ 123.2
Investments in privately-held companies	72.5		72.5		$ 62.7
Cost method investment	30.2		30.2		$ 19
Prepaid expenses and other current assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	58.3		58.3
Restricted Cash and Investments, Noncurrent
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	64.9		64.9
Debt Securities
Restricted Cash and Cash Equivalents Items [Line Items]
OTTI	0	$ 0	0	$ 0
Publicly-traded equity securities
Restricted Cash and Cash Equivalents Items [Line Items]
OTTI	0	0	0	0
Certain Investments In Privately-Held Companies
Restricted Cash and Cash Equivalents Items [Line Items]
Impairment of privately-held investment	$ 0	$ 4.5	$ 0	$ 9.6

Cash Equivalents and Investme45

Cash Equivalents and Investments - Unrealized Loss on Available-for-Sale Securities (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months		$ 978.7
Unrealized loss, less than 12 months		(3.6)
Fair value, 12 months or greater		76.7
Unrealized loss, 12 months or greater		(0.1)
Total fair value, available-for-sale investments in continuous unrealized loss position		1,055.4
Total unrealized loss, available-for-sale investments in continuous unrealized loss position		(3.7)
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	$ 967.7	974.1
Unrealized loss, less than 12 months	(1.5)	(2.9)
Fair value, 12 months or greater	79.3	76.7
Unrealized loss, 12 months or greater	(0.5)	(0.1)
Total fair value, available-for-sale investments in continuous unrealized loss position	1,047	1,050.8
Total unrealized loss, available-for-sale investments in continuous unrealized loss position	(2)	(3)
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	224.2	122.2
Unrealized loss, less than 12 months	(0.3)	(0.2)
Fair value, 12 months or greater	0	0
Unrealized loss, 12 months or greater	0	0
Total fair value, available-for-sale investments in continuous unrealized loss position	224.2	122.2
Total unrealized loss, available-for-sale investments in continuous unrealized loss position	(0.3)	(0.2)
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	361.6	470.8
Unrealized loss, less than 12 months	(0.5)	(1.9)
Fair value, 12 months or greater	59.5	76.7
Unrealized loss, 12 months or greater	(0.3)	(0.1)
Total fair value, available-for-sale investments in continuous unrealized loss position	421.1	547.5
Total unrealized loss, available-for-sale investments in continuous unrealized loss position	(0.8)	(2)
Foreign government debt securities
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	36.6	20.3
Unrealized loss, less than 12 months	(0.1)	(0.1)
Fair value, 12 months or greater	0	0
Unrealized loss, 12 months or greater	0	0
Total fair value, available-for-sale investments in continuous unrealized loss position	36.6	20.3
Total unrealized loss, available-for-sale investments in continuous unrealized loss position	(0.1)	(0.1)
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	89	106.7
Unrealized loss, less than 12 months	(0.2)	(0.3)
Fair value, 12 months or greater	18	0
Unrealized loss, 12 months or greater	(0.2)	0
Total fair value, available-for-sale investments in continuous unrealized loss position	107	106.7
Total unrealized loss, available-for-sale investments in continuous unrealized loss position	(0.4)	(0.3)
U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	256.3	254.1
Unrealized loss, less than 12 months	(0.4)	(0.4)
Fair value, 12 months or greater	1.8	0
Unrealized loss, 12 months or greater	0	0
Total fair value, available-for-sale investments in continuous unrealized loss position	258.1	254.1
Total unrealized loss, available-for-sale investments in continuous unrealized loss position	$ (0.4)	(0.4)
Publicly-traded equity securities
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months		4.6
Unrealized loss, less than 12 months		(0.7)
Fair value, 12 months or greater		0
Unrealized loss, 12 months or greater		0
Total fair value, available-for-sale investments in continuous unrealized loss position		4.6
Total unrealized loss, available-for-sale investments in continuous unrealized loss position		$ (0.7)

Fair Value Measurements (Assets

Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Available-for-sale securities:
Available-for-sale securities	$ 3,475.4	$ 2,782.1
Asset-backed securities
Available-for-sale securities:
Available-for-sale securities	287.8	303
Certificates of deposit
Available-for-sale securities:
Available-for-sale securities	50	66.1
Commercial paper
Available-for-sale securities:
Available-for-sale securities	124	147.7
Corporate debt securities
Available-for-sale securities:
Available-for-sale securities	834.1	844.9
Foreign government debt securities
Available-for-sale securities:
Available-for-sale securities	64.7	33.9
Money market funds
Available-for-sale securities:
Available-for-sale securities	990.7	592.2
Publicly-traded equity securities
Available-for-sale securities:
Available-for-sale securities	0	4.6
Time deposits
Available-for-sale securities:
Available-for-sale securities	411.4	264.6
U.S. government agency securities
Available-for-sale securities:
Available-for-sale securities	156.5	126.7
U.S. government securities
Available-for-sale securities:
Available-for-sale securities	548	390.4
Fair Value, Measurements, Recurring
Derivative assets:
Total assets measured at fair value	3,552.3	2,847.7
Liabilities measured at fair value:
Other accrued liabilities	(0.6)	(4.9)
Total liabilities measured at fair value	(0.6)	(4.9)
Reported Value [Abstract]
Cash equivalents	1,588.8	907.1
Restricted investments	77.1	71.9
Short-term investments	922	752.3
Long-term investments	913.6	1,071.8
Prepaid expenses and other current assets	8.5	0.9
Other long-term assets	42.3	43.7
Fair Value, Measurements, Recurring | Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	8.5	0.9
Liabilities measured at fair value:
Derivative liabilities	(0.6)	(4.9)
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets For Identical Assets (Level 1)
Derivative assets:
Total assets measured at fair value	1,368.7	970.8
Liabilities measured at fair value:
Other accrued liabilities	0	0
Total liabilities measured at fair value	0	0
Reported Value [Abstract]
Cash equivalents	947.9	549.4
Restricted investments	77.1	71.9
Short-term investments	231.9	178
Long-term investments	111.8	171.5
Prepaid expenses and other current assets	0	0
Other long-term assets	0	0
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets For Identical Assets (Level 1) | Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	0	0
Liabilities measured at fair value:
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Remaining Inputs (Level 2)
Derivative assets:
Total assets measured at fair value	2,141.3	1,833.2
Liabilities measured at fair value:
Other accrued liabilities	(0.6)	(4.9)
Total liabilities measured at fair value	(0.6)	(4.9)
Reported Value [Abstract]
Cash equivalents	640.9	357.7
Restricted investments	0	0
Short-term investments	690.1	574.3
Long-term investments	801.8	900.3
Prepaid expenses and other current assets	8.5	0.9
Other long-term assets	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Remaining Inputs (Level 2) | Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	8.5	0.9
Liabilities measured at fair value:
Derivative liabilities	(0.6)	(4.9)
Fair Value, Measurements, Recurring | Significant Other Unobservable Remaining Inputs (Level 3)
Derivative assets:
Total assets measured at fair value	42.3	43.7
Liabilities measured at fair value:
Other accrued liabilities	0	0
Total liabilities measured at fair value	0	0
Reported Value [Abstract]
Cash equivalents	0	0
Restricted investments	0	0
Short-term investments	0	0
Long-term investments	0	0
Prepaid expenses and other current assets	0	0
Other long-term assets	42.3	43.7
Fair Value, Measurements, Recurring | Significant Other Unobservable Remaining Inputs (Level 3) | Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	0	0
Liabilities measured at fair value:
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Asset-backed securities
Available-for-sale securities:
Available-for-sale securities	287.8	303
Fair Value, Measurements, Recurring | Asset-backed securities | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Asset-backed securities | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	287.8	303
Fair Value, Measurements, Recurring | Asset-backed securities | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Certificates of deposit
Available-for-sale securities:
Available-for-sale securities	50	66.1
Fair Value, Measurements, Recurring | Certificates of deposit | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Certificates of deposit | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	50	66.1
Fair Value, Measurements, Recurring | Certificates of deposit | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Commercial paper
Available-for-sale securities:
Available-for-sale securities	124	147.7
Fair Value, Measurements, Recurring | Commercial paper | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Commercial paper | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	124	147.7
Fair Value, Measurements, Recurring | Commercial paper | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Corporate debt securities
Available-for-sale securities:
Available-for-sale securities	834.1	844.9
Fair Value, Measurements, Recurring | Corporate debt securities | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Corporate debt securities | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	834.1	844.9
Fair Value, Measurements, Recurring | Corporate debt securities | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Foreign government debt securities
Available-for-sale securities:
Available-for-sale securities	64.7	33.9
Fair Value, Measurements, Recurring | Foreign government debt securities | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Foreign government debt securities | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	64.7	33.9
Fair Value, Measurements, Recurring | Foreign government debt securities | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Money market funds
Available-for-sale securities:
Available-for-sale securities	990.7	592.2
Fair Value, Measurements, Recurring | Money market funds | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	990.7	592.2
Fair Value, Measurements, Recurring | Money market funds | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Money market funds | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Mutual funds
Available-for-sale securities:
Available-for-sale securities	8.2	8
Trading securities in mutual funds	26.1	21
Fair Value, Measurements, Recurring | Mutual funds | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	8.2	8
Trading securities in mutual funds	26.1	21
Fair Value, Measurements, Recurring | Mutual funds | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	0	0
Trading securities in mutual funds	0	0
Fair Value, Measurements, Recurring | Mutual funds | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Trading securities in mutual funds	0	0
Fair Value, Measurements, Recurring | Publicly-traded equity securities
Available-for-sale securities:
Available-for-sale securities	0	4.6
Fair Value, Measurements, Recurring | Publicly-traded equity securities | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	0	4.6
Fair Value, Measurements, Recurring | Publicly-traded equity securities | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Publicly-traded equity securities | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Time deposits
Available-for-sale securities:
Available-for-sale securities	411.4	264.6
Fair Value, Measurements, Recurring | Time deposits | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Time deposits | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	411.4	264.6
Fair Value, Measurements, Recurring | Time deposits | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | U.S. government agency securities
Available-for-sale securities:
Available-for-sale securities	156.5	126.7
Fair Value, Measurements, Recurring | U.S. government agency securities | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | U.S. government agency securities | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	156.5	126.7
Fair Value, Measurements, Recurring | U.S. government agency securities | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | U.S. government securities
Available-for-sale securities:
Available-for-sale securities	548	390.4
Fair Value, Measurements, Recurring | U.S. government securities | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	343.7	345
Fair Value, Measurements, Recurring | U.S. government securities | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	204.3	45.4
Fair Value, Measurements, Recurring | U.S. government securities | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Total available-for-sale securities
Available-for-sale securities:
Available-for-sale securities	3,475.4	2,782.1
Fair Value, Measurements, Recurring | Total available-for-sale securities | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale securities	1,342.6	949.8
Fair Value, Measurements, Recurring | Total available-for-sale securities | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale securities	2,132.8	1,832.3
Fair Value, Measurements, Recurring | Total available-for-sale securities | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring | Privately-held debt and redeemable preferred stock securities
Available-for-sale securities:
Privately-held debt and redeemable preferred stock securities	42.3	43.7
Fair Value, Measurements, Recurring | Privately-held debt and redeemable preferred stock securities | Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Privately-held debt and redeemable preferred stock securities	0	0
Fair Value, Measurements, Recurring | Privately-held debt and redeemable preferred stock securities | Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Privately-held debt and redeemable preferred stock securities	0	0
Fair Value, Measurements, Recurring | Privately-held debt and redeemable preferred stock securities | Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Privately-held debt and redeemable preferred stock securities	$ 42.3	$ 43.7

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	May 01, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cost method investment	$ 30,200,000	$ 30,200,000		$ 19,000,000
Significant Other Observable Remaining Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt, Fair Value	2,274,800,000	2,274,800,000		2,215,700,000
Privately-held debt and redeemable preferred stock securities | Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss) on investments	0	0
Certain Investments In Privately-Held Companies | Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cost method investment				1,600,000
Cos method investment, fair value				0
Junos Pulse
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Note receivable	$ 58,500,000	$ 58,500,000	$ 58,000,000	$ 132,900,000

Derivative Instruments (Details

Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Derivatives, Notional Amount [Line Items]
Notional amount of foreign currency derivatives	$ 378.7		$ 378.7		$ 172
Non-designated derivatives
Derivatives, Notional Amount [Line Items]
Notional amount of foreign currency derivatives	147.1		$ 147.1		0
Maturities of cash flow hedge derivatives			1 month
Cash flow hedges | Designated as hedge
Derivatives, Notional Amount [Line Items]
Notional amount of foreign currency derivatives	231.6		$ 231.6		$ 172
Maturities of cash flow hedge derivatives			18 months
Gains or losses is expected to be reclassified into earnings within the next 12 months			$ 8.8
Foreign exchange contracts | Cash flow hedges
Derivatives, Notional Amount [Line Items]
Derivative instruments, gain (loss) recognized in other comprehensive income (loss), Effective portion	$ 6.8	$ 0.3	$ 17.6	$ 4.8

Goodwill and Purchased Intang49

Goodwill and Purchased Intangible Assets - Goodwill (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Goodwill [Roll Forward]
Balance as of December 31, 2016	$ 3,081.7
Additions due to business combination	16.7
Other	(2.2)
Balance as of September 30, 2017	$ 3,096.2

Goodwill and Purchased Intang50

Goodwill and Purchased Intangible Assets - Purchased Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 18, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Purchased intangible assets, net	$ 133		$ 133			$ 130.2
Amortization of intangible assets	$ 4.1	$ 4.8	$ 12.6	$ 12.9
Cyphort
Finite-Lived Intangible Assets [Line Items]
Intangible acquired					$ 15.4

Other Financial Information - I

Other Financial Information - Inventories, Net (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Inventory [Line Items]
Production and service materials	$ 72.6	$ 75.6
Finished goods	18.3	19.9
Inventory	90.9	95.5
Prepaid expenses and other current assets
Schedule Of Inventory [Line Items]
Inventory	84.9	91.4
Other Noncurrent Assets
Schedule Of Inventory [Line Items]
Inventory	$ 6	$ 4.1

Other Financial Information - O

Other Financial Information - Other Long Term Assets (Details) - USD ($) $ in Millions	May 01, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Apr. 01, 2017	Dec. 31, 2016	Oct. 01, 2014
Other Financial Information [Line Items]
Proceeds from Pulse note receivable				$ 75	$ 0
Junos Pulse
Other Financial Information [Line Items]
Consideration								$ 230.7
Cash Consideration								105.7
Working capital adjustment								19.3
Note receivable carrying value								$ 125
Proceeds from Pulse note receivable	$ 75
Note receivable	$ 58	$ 58.5		58.5			$ 132.9
Interest income		$ 1.6	$ 2.7	$ 6.5	$ 8
Prepaid expenses and other current assets | Junos Pulse
Other Financial Information [Line Items]
Note receivable carrying value						$ 75

Other Financial Information - W

Other Financial Information - Warranties (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance as of December 31, 2016	$ 41.3
Provisions made during the period	29.6
Actual costs incurred during the period	(41.5)
Balance as of September 30, 2017	$ 29.4

Other Financial Information - D

Other Financial Information - Deferred Revenue (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Deferred product revenue:
Deferred product revenue, net	$ 1,462.9	$ 1,481.1
Deferred service revenue
Deferred service revenue	1,462.9	1,481.1
Deferred revenue	1,462.9	1,481.1
Reported as:
Current	977.4	1,032
Long-term	485.5	449.1
Deferred revenue	1,462.9	1,481.1
Deferred product revenue:
Deferred product revenue:
Undelivered product commitments and other product deferrals	309.3	302.4
Distributor inventory and other sell-through items	61.9	74.2
Deferred gross product revenue	371.2	376.6
Deferred cost of product revenue	(47.5)	(53.7)
Deferred product revenue, net	323.7	322.9
Deferred service revenue
Deferred service revenue	323.7	322.9
Deferred revenue	323.7	322.9
Reported as:
Deferred revenue	323.7	322.9
Deferred service revenue
Deferred product revenue:
Deferred product revenue, net	1,139.2	1,158.2
Deferred service revenue
Deferred service revenue	1,139.2	1,158.2
Deferred revenue	1,139.2	1,158.2
Reported as:
Deferred revenue	$ 1,139.2	$ 1,158.2

Other Financial Information -55

Other Financial Information - Other Income (Expense), Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Financial Information [Abstract]
Interest income	$ 14.7	$ 9.1	$ 37.1	$ 25.5
Interest expense	(25.3)	(25.1)	(75.6)	(72.6)
Gain on investments, net	4.7	1.9	6.7	0.1
Other	0.8	0.7	(2)	(0.2)
Other expense, net	$ (5.1)	$ (13.4)	$ (33.8)	$ (47.2)

Restructuring Charges (Charges

Restructuring Charges (Charges and Changes to Restructuring)(Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance			$ 1.2
Charges	$ 2	$ 0.8	29.4	$ 3.2
Cash Payments			(25.9)
Other			0
Restructuring liability, ending balance	4.7		4.7
Severance
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance			0.7
Charges			26
Cash Payments			(25.5)
Other			(0.1)
Restructuring liability, ending balance	1.1		1.1
Severance | 2017 Restructuring Plan
Restructuring Reserve [Roll Forward]
Charges	0.6		26
Contract terminations and other
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance			0.5
Charges			3.4
Cash Payments			(0.4)
Other			0.1
Restructuring liability, ending balance	3.6		3.6
Contract terminations and other | 2017 Restructuring Plan
Restructuring Reserve [Roll Forward]
Charges	$ 1.4		$ 3.4

Debt and Financing (Summary of

Debt and Financing (Summary of Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,150
Unaccreted discount and debt issuance costs	(14.3)
Long-term debt	$ 2,135.7	$ 2,133.7
Redemption percent due to change in control (percentage)	101.00%
3.125% fixed-rate notes, due February 2019
Debt Instrument [Line Items]
Long-term debt, gross	$ 350
Effective Interest Rates	3.36%
Long-term debt, stated interest rate	3.125%
3.300% fixed-rate notes, due June 2020
Debt Instrument [Line Items]
Long-term debt, gross	$ 300
Effective Interest Rates	3.47%
Long-term debt, stated interest rate	3.30%
4.600% fixed-rate notes, due March 2021
Debt Instrument [Line Items]
Long-term debt, gross	$ 300
Effective Interest Rates	4.69%
Long-term debt, stated interest rate	4.60%
4.500% fixed-rate notes, due March 2024, issued March 2014
Debt Instrument [Line Items]
Long-term debt, gross	$ 350
Effective Interest Rates	4.63%
Long-term debt, stated interest rate	4.50%
4.500% fixed-rate notes, due March 2024, issued February 2016
Debt Instrument [Line Items]
Long-term debt, gross	$ 150
Effective Interest Rates	4.87%
Long-term debt, stated interest rate	4.50%
4.350% fixed-rate notes, due June 2025
Debt Instrument [Line Items]
Long-term debt, gross	$ 300
Effective Interest Rates	4.47%
Long-term debt, stated interest rate	4.35%
5.950% fixed-rate notes, due March 2041
Debt Instrument [Line Items]
Long-term debt, gross	$ 400
Effective Interest Rates	6.03%
Long-term debt, stated interest rate	5.95%

Debt and Financing - Revolving

Debt and Financing - Revolving Credit Facility (Details) - Revolving Credit Facility - USD ($)	Jun. 27, 2014	Sep. 30, 2017
Line of Credit Facility [Line Items]
Revolving credit facility limit	$ 500,000,000
Revolving credit facility, additional borrowing capacity	$ 200,000,000
Line of credit, outstanding		$ 0
Base Rate | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.00%
Base Rate | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.50%
Eurodollar | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.90%
Eurodollar | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.50%

Debt and Financing - Customer F

Debt and Financing - Customer Financing Arrangements (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Sale of receivable	$ 77.3	$ 59.3	$ 132.6	$ 73.4
Proceeds from sale and collection of receivables	57.6	$ 30	113.3	$ 40.8
Receivables from sale of receivables	$ 32.9		$ 32.9		$ 13.6
Minimum
Debt Instrument [Line Items]
Number of days due from receivable			1 day
Maximum
Debt Instrument [Line Items]
Number of days due from receivable			90 days

Equity - Cash Dividends on Shar

Equity - Cash Dividends on Shares of Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 25, 2017	Apr. 25, 2017	Jan. 26, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stockholders' Equity Note [Abstract]
Cash dividends declared per common stock (in dollars per share)	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.30	$ 0.30
Common stock dividends paid						$ 113.5

Equity - Stock Repurchase Activ

Equity - Stock Repurchase Activities (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Feb. 28, 2017	Oct. 31, 2014	Feb. 28, 2014
Accelerated Share Repurchases [Line Items]
Shares repurchased and retired related to net issuances		$ 1,400,000		$ 11,000,000
2014 Stock Repurchase Program
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount					$ 4,400,000,000		$ 2,100,000,000
Additional amount authorized under Stock Repurchase Plan					$ 500,000,000	$ 1,800,000,000
Stock repurchased (in shares)	5	4.9	13.5	13.5
Average price per share (in dollars per share)	$ 28.16	$ 23.04	$ 28.85	$ 23.25
Amount repurchased	$ 140,000,000	$ 112,400,000	$ 390,000,000	$ 312,900,000
Stock repurchase program, remaining authorized repurchase amount	$ 329,700,000		$ 329,700,000
Stock Repurchase Program 2014, Accelerated Share Repurchase
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount							$ 1,200,000,000

Equity - Components of Accumula

Equity - Components of Accumulated Other Comprehensive (Loss) Income, Net of Tax (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive gains before reclassifications	$ 35.3
Amount reclassified from accumulated other comprehensive loss	(4.4)
Other comprehensive (loss) gains, net	30.9
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of December 31, 2016	(37.3)
Balance as of September 30, 2017	(6.4)
Unrealized Gains on Available-for- Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of December 31, 2016	16.6
Other comprehensive gains before reclassifications	1.4
Amount reclassified from accumulated other comprehensive loss	(2)
Other comprehensive (loss) gains, net	(0.6)
Balance as of September 30, 2017	16
Unrealized (Losses) Gains on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of December 31, 2016	(4.5)
Other comprehensive gains before reclassifications	14.6
Amount reclassified from accumulated other comprehensive loss	(2.4)
Other comprehensive (loss) gains, net	12.2
Balance as of September 30, 2017	7.7
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of December 31, 2016	(49.4)
Other comprehensive gains before reclassifications	19.3
Amount reclassified from accumulated other comprehensive loss	0
Other comprehensive (loss) gains, net	19.3
Balance as of September 30, 2017	$ (30.1)

Employee Benefit Plans ( Equity

Employee Benefit Plans ( Equity Incentive Plan and Stock Option Activity) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	May 25, 2017	Sep. 30, 2017
Number of Shares
Balance at beginning of period (in shares)		2.4
Exercised (in shares)		(0.5)
Expired/canceled (in shares)		(0.8)
Balance at end of period (in shares)		1.1
Weighted Average Exercise Price per Share
Balance at beginning of period (in dollars per share)		$ 29.20
Exercised (in dollars per share)		14.97
Expired/canceled (in dollars per share)		31.09
Balance at end of period (in dollars per share)		$ 34.31
Weighted average remaining contractual term at end of period		1 year 1 month 6 days
Aggregate intrinsic value at end of period		$ 3.1
Vested or expected-to-vest options at end of period (in shares)		1.1
Vested or expected-to-vest options, weighted average exercise price at end of period (in dollars per share)		$ 34.31
Vested and expected-to-vest options, weighted average remaining contractual term at end of period		1 year 1 month 6 days
Vested or expected-to-vest options, aggregate intrinsic value at end of period		$ 3.1
Exercisable options at end of period (in shares)		1
Exercisable options, weighted average exercise price at end of period (in dollars per share)		$ 35.56
Exercisable options, weighted average remaining contractual term at end of period		9 months 18 days
Exercisable options, aggregate intrinsic value at end of period		$ 2.1
Equity incentive plan 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized (shares)	23
Share-Based Compensation Plans
Number of shares available for future issuance		35.3
Employee stock purchase plan 2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized (shares)	9
Share-Based Compensation Plans
Number of shares available for future issuance		11.2

Employee Benefit Plans - Equity

Employee Benefit Plans - Equity Instruments Other Than Options (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 25, 2017	Apr. 25, 2017	Jan. 26, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Weighted Average Grant-Date Fair Value per Share
Cash dividends declared per common stock (in dollars per share)	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.30	$ 0.30
Common stock dividends paid						$ 113.5
Employee stock purchase plan 2008
Employee Stock Purchase Plan
Expiration period for ESPP						6 months
Stock issued during period, shares, employee stock purchase plans (in shares)				1,200,000	1,400,000	2,700,000	2,700,000
Average price of common stock, per share (in dollars per share)				$ 22.79	$ 19.29	$ 20.83	$ 19.66
RSUs, RSAs, and PSAs
Number of Shares
Balance at beginning of period (in shares)						20,900,000
Balance at end of period (in shares)				19,300,000		19,300,000
Weighted Average Grant-Date Fair Value per Share
Balance at beginning of period (in dollars per share)						$ 24.05
Balance at end of period (in dollars per share)				$ 25.23		$ 25.23
Weighted Average Remaining Contractual Term (In Years)						1 year 1 month 20 days
Aggregate Intrinsic Value				$ 537.1		$ 537.1
Restricted Stock Units (RSUs)
Number of Shares
Granted (in shares)						6,600,000
Assumed in acquisitions (in shares)						100,000
Vested (in shares)						(6,000,000)
Canceled (in shares)						(1,500,000)
Weighted Average Grant-Date Fair Value per Share
Granted (in dollars per share)						$ 27.56
Assumed in acquisition (in dollars per share)						26.91
Vested (in dollars per share)						23.81
Canceled (in dollars per share)						$ 24.57
Performance shares (PSAs)
Number of Shares
Granted (in shares)						600,000
Vested (in shares)						(500,000)
Canceled (in shares)						(500,000)
Weighted Average Grant-Date Fair Value per Share
Granted (in dollars per share)						$ 27.37
Vested (in dollars per share)						24.29
Canceled (in dollars per share)						$ 25.11
Aggregate number of shares subject to PSAs granted						400,000
Minimum shares to be issued on achievement of performance goals in respect of PSAs (shares)						0
Maximum shares to be issued on achievement of performance goals in respect of PSAs (shares)						600,000
Restricted stock awards (RSAs)
Number of Shares
Vested (in shares)						(400,000)
Weighted Average Grant-Date Fair Value per Share
Vested (in dollars per share)						$ 22.80

Employee Benefit Plans - Share

Employee Benefit Plans - Share Based Compensation by Cost and Expense Categories (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	$ 45	$ 55.6	$ 151.1	$ 163
Stock options
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	0.2	1.5	0.5	3.7
RSUs, RSAs, and PSAs
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	41	50.3	138.9	147.6
ESPP
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	3.8	3.8	11.7	11.7
Cost of revenues - Product
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	1.5	1.5	3.8	4.9
Cost of revenues - Service
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	3.9	3.5	13.5	11.3
Research and development
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	18.5	27.2	67.4	89
Sales and marketing
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	13.7	17.5	45.3	40.7
General and administrative
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	$ 7.4	$ 5.9	$ 21.1	$ 17.1

Employee Benefit Plans - Shar66

Employee Benefit Plans - Share Based Compensation by Share Based Payment Award Types (Details) - Restricted Stock Units, Restricted Stock Award and Performance Share Award $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Cost	$ 309.8
Weighted Average Period (In Years)	1 year 7 months 18 days

Segments (Revenue by product) (

Segments (Revenue by product) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)segment	Sep. 30, 2016USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			1
Product	$ 869.7	$ 928.2	$ 2,615.8	$ 2,543.3
Service	388.1	357.1	1,171.9	1,061.2
Total net revenues	1,257.8	1,285.3	3,787.7	3,604.5
Routing
Segment Reporting Information [Line Items]
Product	585.8	620.2	1,679.9	1,699
Switching
Segment Reporting Information [Line Items]
Product	212.6	222.5	730.2	607.2
Security
Segment Reporting Information [Line Items]
Product	71.3	85.5	205.7	237.1
Total product
Segment Reporting Information [Line Items]
Product	869.7	928.2	2,615.8	2,543.3
Total service
Segment Reporting Information [Line Items]
Service	$ 388.1	$ 357.1	$ 1,171.9	$ 1,061.2

Segments - Revenues by Customer

Segments - Revenues by Customer Vertical (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Total net revenues	$ 1,257.8	$ 1,285.3	$ 3,787.7	$ 3,604.5
Cloud
Segment Reporting Information [Line Items]
Total net revenues	344.9	359.4	1,056.1	911.5
Telecom/Cable
Segment Reporting Information [Line Items]
Total net revenues	576.9	599.4	1,707.8	1,688.5
Strategic Enterprise
Segment Reporting Information [Line Items]
Total net revenues	$ 336	$ 326.5	$ 1,023.8	$ 1,004.5

Segments - Geographic (Details)

Segments - Geographic (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Total net revenues	$ 1,257.8	$ 1,285.3	$ 3,787.7	$ 3,604.5
Total Americas
Segment Reporting Information [Line Items]
Total net revenues	729.2	745	2,241.6	2,093.2
United States
Segment Reporting Information [Line Items]
Total net revenues	668.8	684.6	2,076	1,924.9
Other
Segment Reporting Information [Line Items]
Total net revenues	60.4	60.4	165.6	168.3
Europe, Middle East, and Africa
Segment Reporting Information [Line Items]
Total net revenues	298.6	338	871.3	923.5
Asia Pacific
Segment Reporting Information [Line Items]
Total net revenues	$ 230	$ 202.3	$ 674.8	$ 587.8

Income Taxes (Details of Income

Income Taxes (Details of Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income before income taxes	$ 225.8	$ 236.6	$ 611.6	$ 555.3
Income tax provision	$ 60.1	$ 64.2	$ 157.3	$ 151.5
Effective tax rate	26.60%	27.10%	25.70%	27.30%
Unrecognized tax benefits	$ 236.7		$ 236.7
Unrecognized tax benefits that would impact effective tax rate	204.2		204.2
Unrecognized tax benefits could decrease up to	$ 67		$ 67

Net Income Per Share (Basic and

Net Income Per Share (Basic and Diluted Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net income	$ 165.7	$ 172.4	$ 454.3	$ 403.8
Denominator:
Weighted-average shares used to compute basic net income per share (in shares)	378.3	381	380	382.3
Dilutive effect of employee stock awards (in shares)	4.4	3.5	6.5	5.6
Weighted-average shares used to compute diluted net income per share (in shares)	382.7	384.5	386.5	387.9
Net income per share
Basic (in dollars per share)	$ 0.44	$ 0.45	$ 1.20	$ 1.06
Diluted, (in dollars per share)	$ 0.43	$ 0.45	$ 1.18	$ 1.04
Anti-dilutive shares	1	2.7	1.2	2.7

Commitments and Contingencies -

Commitments and Contingencies - Commitments (Details) - Damages from Product Defects - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Supplier component remediation liability	$ 0.8	$ 10.8
Supplier component remediation, estimated period that components may begin to fail	18 months

Commitments and Contingencies73

Commitments and Contingencies - Guarantees (Details) - Indemnification Agreement - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Guarantor obligations, current carrying value	$ 20.1	$ 28.9
Guarantor obligations, reversal of accrual recorded previously	$ 15

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Oct. 24, 2017	Jul. 25, 2017	Apr. 25, 2017	Jan. 26, 2017	Nov. 07, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Subsequent Event [Line Items]
Cash dividends declared per common stock (in dollars per share)		$ 0.10	$ 0.10	$ 0.10		$ 0.10	$ 0.10	$ 0.30	$ 0.30
Subsequent Event
Subsequent Event [Line Items]
Cash dividends declared per common stock (in dollars per share)	$ 0.10
Common Stock | Subsequent Event
Subsequent Event [Line Items]
Stock repurchased during period (in shares)					4
Shares repurchased during the period					$ 100
Average price per share (in dollars per share)					$ 24.80
Shares settled (in shares)					3.6
Stock repurchase program, remaining authorized repurchase amount					$ 229.7
Minimum | Severance | Subsequent Event
Subsequent Event [Line Items]
Restructuring related expenses, expected					23
Maximum | Severance | Subsequent Event
Subsequent Event [Line Items]
Restructuring related expenses, expected					$ 27