Juniper Networks (JNPR) 10-K 22 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Feb. 15, 2019	Jun. 29, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	JUNIPER NETWORKS INC
Entity Central Index Key	1,043,604
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		347,922,460
Entity Public Float			$ 9,483

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net revenues:
Net revenues	$ 4,647.5	$ 5,027.2	$ 4,990.1
Cost of revenues:
Cost of revenues	1,906.3	1,955.1	1,885.6
Gross margin	2,741.2	3,072.1	3,104.5
Operating expenses:
Research and development	1,003.2	980.7	1,013.7
Sales and marketing	927.4	950.2	972.9
General and administrative	231.1	227.5	224.9
Restructuring charges	7.3	65.6	3.3
Total operating expenses	2,169	2,224	2,214.8
Operating income	572.2	848.1	889.7
Other expense, net	(39.5)	(36.3)	(62.3)
Income before income taxes	532.7	811.8	827.4
Income tax (benefit) provision	(34.2)	505.6	234.7
Net income	$ 566.9	$ 306.2	$ 592.7
Net income per share:
Basic (in dollars per share)	$ 1.62	$ 0.81	$ 1.55
Diluted (in dollars per share)	$ 1.60	$ 0.80	$ 1.53
Shares used in computing net income per share:
Basic (in shares)	349	377.7	381.7
Diluted (in shares)	354.4	384.2	387.8
Product
Net revenues:
Net revenues	$ 3,107.1	$ 3,446.2	$ 3,528.9
Cost of revenues:
Cost of revenues	1,277.2	1,360.9	1,326.2
Service
Net revenues:
Net revenues	1,540.4	1,581	1,461.2
Cost of revenues:
Cost of revenues	$ 629.1	$ 594.2	$ 559.4

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 566.9	$ 306.2	$ 592.7
Available-for-sale debt securities:
Change in net unrealized gains and losses, net of tax benefit (provision) of $1.0, ($4.0), and $0.7 for 2018, 2017, and 2016, respectively	0.6	4.5	0.8
Net realized (gains) losses reclassified into net income, net of tax provisions of zero, $0.9, and $0.5 for 2018, 2017, and 2016, respectively	0.9	(2.1)	(1.2)
Net change on available-for-sale debt securities, net of tax	1.5	2.4	(0.4)
Cash flow hedges:
Change in net unrealized gains and losses, net of tax benefit (provision) of $2.3, ($4.4), and ($0.8) for 2018, 2017, and 2016, respectively	(6.4)	15.7	(2.1)
Net realized (gains) losses reclassified into net income, net of tax provisions of $0.3, $2.4, and $0.7 for 2018, 2017, and 2016, respectively	(1.2)	(5.2)	(1.1)
Net change on cash flow hedges, net of tax	(7.6)	10.5	(3.2)
Change in foreign currency translation adjustments	(12.4)	19	(14.5)
Other comprehensive (loss) income, net of tax	(18.5)	31.9	(18.1)
Comprehensive income	$ 548.4	$ 338.1	$ 574.6

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Change in net unrealized gains and losses, net of tax benefit (provision) of $1.0, ($4.0), and $0.7 for 2018, 2017, and 2016, respectively	$ 1	$ (4)	$ 0.7
Net realized (gains) losses reclassified into net income, net of tax provisions of zero, $0.9, and $0.5 for 2018, 2017, and 2016, respectively	0	0.9	0.5
Change in net unrealized gains and losses, net of tax benefit (provision) of $2.3, ($4.4), and ($0.8) for 2018, 2017, and 2016, respectively	2.3	(4.4)	(0.8)
Net realized (gains) losses reclassified into net income, net of tax provisions of $0.3, $2.4, and $0.7 for 2018, 2017, and 2016, respectively	$ 0.3	$ 2.4	$ 0.7

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 2,489	$ 2,006.5
Short-term investments	1,070.1	1,026.1
Accounts receivable, net of allowance for doubtful accounts of $4.9 and $5.7 as of December 31, 2018 and 2017, respectively	754.6	852
Prepaid expenses and other current assets	268.1	299.9
Total current assets	4,581.8	4,184.5
Property and equipment, net	951.7	1,021.1
Long-term investments	199	988.4
Purchased intangible assets, net	118.5	128.1
Goodwill	3,108.8	3,096.2
Other long-term assets	403.5	415.5
Total assets	9,363.3	9,833.8
Current liabilities:
Accounts payable	208.8	217.6
Accrued compensation	221	186
Deferred revenue	829.3	1,030.3
Short-term portion of long-term debt	349.9	0
Other accrued liabilities	233.5	304.3
Total current liabilities	1,842.5	1,738.2
Long-term debt	1,789.1	2,136.3
Long-term deferred revenue	384.3	509
Long-term income taxes payable	404.4	650.6
Other long-term liabilities	119.8	118.8
Total liabilities	4,540.1	5,152.9
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; 346.4 shares and 365.5 shares issued and outstanding as of December 31, 2018 and 2017, respectively	0	0
Additional paid-in capital	7,672.8	8,042.1
Accumulated other comprehensive loss	(18.2)	(5.4)
Accumulated deficit	(2,831.4)	(3,355.8)
Total stockholders' equity	4,823.2	4,680.9
Total liabilities and stockholders' equity	$ 9,363.3	$ 9,833.8

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable, current	$ 4.9	$ 5.7
Convertible preferred stock - par value (in USD per share)	$ 0.00001	$ 0.00001
Convertible preferred stock - shares authorized (in shares)	10,000,000	10,000,000
Convertible preferred stock - issued (in shares)	0	0
Convertible preferred stock - outstanding (in shares)	0	0
Common stock - par value (in USD per share)	$ 0.00001	$ 0.00001
Common stock - shares authorized (in shares)	1,000,000,000	1,000,000,000
Common stock - shares issued (in shares)	346,400,000	365,500,000
Common stock - outstanding (in shares)	346,400,000	365,500,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 566.9	$ 306.2	$ 592.7
Adjustments to reconcile net income to net cash provided by operating activities:
Share-based compensation expense	217.1	187.5	224.6
Depreciation, amortization, and accretion	210.5	225.6	206.7
Deferred income taxes	42.6	(139.6)	55.9
Other	9.6	(14.5)	3.5
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable, net	96.3	203.8	(263.5)
Prepaid expenses and other assets	(70.9)	43	(43.6)
Accounts payable	3.5	(10.1)	66.6
Accrued compensation	41.4	(42.8)	(19.5)
Income taxes payable	(269.2)	447.3	3.1
Other accrued liabilities	(11.4)	(2.1)	(1.6)
Deferred revenue	24.7	55	301.7
Net cash provided by operating activities	861.1	1,259.3	1,126.6
Cash flows from investing activities:
Purchases of property and equipment	(147.4)	(151.2)	(214.7)
Purchases of available-for-sale debt securities	(1,228.5)	(1,882.9)	(1,598)
Proceeds from sales of available-for-sale debt securities	1,070.2	944	1,182.1
Proceeds from maturities and redemptions of available-for-sale debt securities	910.2	741.6	342.3
Purchases of equity securities	(17.5)	(14.9)	(25.2)
Proceeds from sales of equity securities	36.9	12.4	9.5
Proceeds from Pulse note receivable	0	75	0
Subsequent payments related to acquisitions in prior years	(42.7)	0	0
Payments for business acquisitions, net of cash and cash equivalents acquired	(16.4)	(27)	(113)
Net cash provided by (used in) investing activities	564.8	(303)	(417)
Cash flows from financing activities:
Repurchase and retirement of common stock	(756.6)	(725.8)	(324.6)
Proceeds from issuance of common stock	56.9	64.5	62.3
Payment of dividends	(249.3)	(150.4)	(152.5)
Change in customer financing arrangement	(16.9)	16.9	0
Payment of debt	0	0	(300)
Issuance of debt, net	0	0	494
Other	2.7	0	15.5
Net cash used in financing activities	(968.6)	(794.8)	(236.3)
Effect of foreign currency exchange rates on cash, cash equivalents, and restricted cash	(10.6)	17	(14)
Net increase in cash, cash equivalents, and restricted cash	446.7	178.5	459.3
Cash, cash equivalents, and restricted cash at beginning of period	2,505.8	2,059.1	1,880.6
Cash, cash equivalents, and restricted cash at end of period	2,059.1	1,880.6	1,421.3
Supplemental disclosures of cash flow information:
Cash paid for interest, net of amounts capitalized	94	93.9	92.8
Cash paid for income taxes, net	181	193.5	173.9
Non-cash investing and financing activities:
Construction costs for building with financing obligation	$ 0	$ 0	$ 15.3

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Common Stock and Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (shares) at Dec. 31, 2015		384
Stockholders' equity, Beginning balance at Dec. 31, 2015	$ 4,574.4		$ 8,334.8	$ (19.2)	$ (3,741.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	592.7				592.7
Other comprehensive income (loss), net	(18.1)			(18.1)
Issuance of common stock (in shares)		11.1
Issuance of common stock	62.3		62.3
Repurchase and retirement of common stock (in shares)		(14)
Repurchase and retirement of common stock	(324.6)		(191.3)		(133.3)
Share-based compensation expense	222.4		222.4
Tax effects from employee stock option plans	5.9		5.9
Payment of cash dividends	(152.5)		(152.5)
Ending balance (shares) at Dec. 31, 2016		381.1
Stockholders' equity, Ending balance at Dec. 31, 2016	4,962.5		8,281.6	(37.3)	(3,281.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	306.2				306.2
Other comprehensive income (loss), net	31.9			31.9
Issuance of common stock (in shares)		10.7
Issuance of common stock	64.5		64.5
Repurchase and retirement of common stock (in shares)		(26.3)
Repurchase and retirement of common stock	(725.8)		(354.6)		(371.2)
Share-based compensation expense	188.2		188.2
Payment of cash dividends	$ (150.4)		(150.4)
Ending balance (shares) at Dec. 31, 2017	365.5	365.5
Stockholders' equity, Ending balance at Dec. 31, 2017	$ 4,680.9		8,042.1	(5.4)	(3,355.8)
Beginning balance (shares) at Dec. 31, 2017	365.5	365.5
Stockholders' equity, Beginning balance at Dec. 31, 2017	$ 4,680.9		8,042.1	(5.4)	(3,355.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	566.9				566.9
Other comprehensive income (loss), net	(18.5)			(18.5)
Issuance of common stock (in shares)		10.4
Issuance of common stock	56.9		56.9
Repurchase and retirement of common stock (in shares)		(29.5)
Repurchase and retirement of common stock	(756.6)		(395.1)		(361.5)
Share-based compensation expense	218.2		218.2
Payment of cash dividends	$ (249.3)		(249.3)
Reclassification of tax effects upon adoption of ASU 2018-02				5.7	(5.7)
Ending balance (shares) at Dec. 31, 2018	346.4	346.4
Stockholders' equity, Ending balance at Dec. 31, 2018	$ 4,823.2		$ 7,672.8	$ (18.2)	(2,831.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative adjustment upon adoption of ASU, net | Accounting Standards Update 2014-09	$ 324.7				$ 324.7

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	Dec. 26, 2018	Sep. 25, 2018	Jun. 22, 2018	Mar. 22, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Stockholders' Equity [Abstract]
Payments of cash dividends (in dollars per share)	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.72	$ 0.40	$ 0.40

Description of Business and Bas

Description of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation Description of Business Juniper Networks, Inc. (the “Company” or “Juniper”) designs, develops, and sells products and services for high-performance networks, to enable customers to build scalable, reliable, secure and cost-effective networks for their businesses, while achieving agility and improved operating efficiency through automation. The Company sells high-performance routing, switching, and security networking products and service offerings to customers within its verticals: Cloud, Service Provider, and Enterprise who view the network as critical to their success. Basis of Presentation The Consolidated Financial Statements, which include the Company and its wholly-owned subsidiaries, are prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). All intercompany balances and transactions have been eliminated. The Company adopted Financial Accounting Standards Board ("FASB") ASU No. 2016-18 (Topic 230) Statement of Cash Flow: Restricted Cash , effective January 1, 2018, using the retrospective transition method. Restricted cash of $47.4 million and $52.6 million has been included within cash, cash equivalents, and restricted cash when reconciling the beginning and ending total amounts, respectively, on the statement of cash flows for the year ended December 31, 2017, and restricted cash of $0.4 million and $47.4 million has been included within cash, cash equivalents, and restricted cash when reconciling the beginning and ending total amounts, respectively, on the statement of cash flows for the year ended December 31, 2016, to conform to the current period presentation. The adoption did not have a material impact on the cash flow activity presented on the Company's Consolidated Statement of Cash Flows for the years ended December 31, 2017 and 2016. See Note 4, Cash Equivalents and Investments , for a reconciliation of the cash balances within the Consolidated Statements of Cash Flows to the Consolidated Balance Sheets.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Use of Estimates 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 Consolidated Financial Statements and the accompanying notes. The Company bases its estimates and assumptions on current facts, historical experience, and various other factors that it believes are reasonable under the circumstances, to determine the carrying values of assets and liabilities that are not readily apparent from other sources. To the extent there are material differences between the Company's estimates and the actual results, the Company's future consolidated results of operation may be affected. Cash, Cash Equivalents, and Investments Cash and Cash Equivalents Cash and cash equivalents consist of cash on hand, demand deposits with banks, highly liquid investments in money market funds, commercial paper, government securities, certificates of deposits, time deposits, and corporate debt securities, which are readily convertible into cash. All highly liquid investments with original maturities of three months or less from Juniper's purchase date are classified as cash equivalents. Investments in Available-for-Sale Debt Securities The Company's investments in debt securities are classified as available-for-sale and include the Company's fixed income securities and investments in privately-held companies, consisting of debt and redeemable preferred stock securities. Fixed income securities are initially recorded at cost and periodically adjusted to fair value in the Consolidated Balance Sheets. Unrealized gains and losses on these investments are reported as a separate component of accumulated other comprehensive loss in the Consolidated Balance Sheets. Realized gains and losses are determined based on the specific identification method and are reported in the Consolidated Statements of Operations. Fixed income securities primarily consist of asset-backed securities, certificate of deposits, commercial paper, corporate debt securities, time deposits, foreign government debt securities, U.S. government agency securities, and U.S. treasury securities. The Company periodically evaluates these investments to determine if impairment charges are required. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value has been less than the Company's cost basis, the investment's financial condition, and the near-term prospects of the investee. If the Company determines that the decline in an investment's value is other than temporary, the difference is recognized as an impairment loss in its Consolidated Statements of Operations. The Company's privately-held debt and redeemable preferred stock securities are included in other long-term assets in the Consolidated Balance Sheets and are recorded at fair value. Fair value is reassessed when the Company is made aware of information indicating a change in the enterprise value of the investee, including known acquisition offers, subsequent funding rounds, and investee's plans for liquidation. The Company periodically evaluates these securities for indicators of impairment, including the inability to recover a portion of or the entire carrying amount of the investment, the inability of the investee to sustain earnings, the reduction in or termination of financial commitment to the investee from other investors, the intention to sell the investment, and whether it is more likely than not that the Company will be required to sell the investment before recovery of the entire amortized cost basis. If the Company determines that the decline in an investment's value is other than temporary, the difference is recognized as an impairment loss in its Consolidated Statements of Operations. Investments in Equity Securities The Company's investments in equity securities with readily determinable fair values consist of money market funds, the non-qualified compensation plan ("NQDC") that is invested in mutual funds, and investments in public companies. These investments are measured at fair value with changes in fair value recognized in the Consolidated Statements of Operations. Equity securities without readily determinable fair values include the Company's investments in privately-held companies consisting of non-redeemable preferred stock and common stock securities. The Company accounts for these securities at cost, adjusted for changes from observable transactions for identical or similar investments of the same issuer, less impairments. Fair value of these equity securities is reassessed when the Company identifies observable price changes indicating that an adjustment upward or downward to the carrying value is necessary. Any observable changes in fair value are recognized in earnings as of the date that the observable transaction took place, rather than the current reporting date. In addition, the Company periodically evaluates equity securities without readily determinable fair values to determine if impairment charges are required by evaluating whether an event or change in circumstance has occurred that may have a significant adverse effect on the fair value of the investment. A qualitative assessment is performed each reporting period to assess whether there are any impairment indicators, including, but not limited to, significant deterioration in the investee's earnings performance; credit rating; asset quality or business prospects; adverse change in the regulatory, economic, or technological environment; change in the general market condition of the geographic area or industry; acquisition offers; and the ability to continue as a going concern. If such indicators are present, the Company estimates the fair value of impaired investments and recognizes an impairment loss in the Consolidated Statement of Operations equal to the difference between the carrying value and fair value. Fair Value Fair value is defined as the price that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value, the Company considers the principal or most advantageous market in which it transacts, and considers assumptions that market participants would use when pricing the asset or liability. The Company applies the following fair value hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1 – Quoted prices in active markets for identical assets or liabilities. Level 2 – Quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. These inputs are valued using market based approaches. Level 3 – Inputs are unobservable inputs based on the Company’s assumptions. These inputs, if any, are valued using internal financial models. Derivatives The Company uses derivatives to partially offset its market exposure to fluctuations in certain foreign currencies. The Company does not enter into derivatives for speculative or trading purposes. The Company uses foreign currency forward contracts to hedge certain forecasted foreign currency transactions relating to operating expenses. These derivatives are designated as cash flow hedges. These derivatives are carried at fair value and the effective portion of the derivative's gain or loss is initially reported as a component of accumulated other comprehensive loss, and upon occurrence of the forecasted transaction, is subsequently reclassified into the costs of services or operating expense line item to which the hedged transaction relates. The Company records any ineffectiveness of the hedging instruments in other expense, net, on its Consolidated Statements of Operations. Cash flows from such hedges are classified as operating activities. The Company also uses foreign currency forward contracts to mitigate variability in gains and losses generated from the re-measurement of certain monetary assets and liabilities denominated in non-functional currencies. These derivatives are carried at fair value with changes recorded in other expense, net in the Consolidated Statements of Operations in the same period as the changes in the fair value from the re-measurement of the underlying assets and liabilities. Cash flows from such derivatives are classified as operating activities. The Company presents its derivative assets and derivative liabilities on a gross basis in the Consolidated Balance Sheets. However, under agreements containing provisions on netting with certain counterparties of foreign exchange contracts, subject to applicable requirements, the Company is allowed to net-settle transactions on the same date in the same currency, with a single net amount payable by one party to the other. The Company is neither required to pledge nor entitled to receive cash collateral related to these derivative transactions. Inventory Inventory consists primarily of component parts to be used in the manufacturing process and finished goods in-transit, and is stated at the lower of cost or net realizable value. Cost is computed using standard cost, which approximates actual cost, on a first-in, first-out basis. A charge is recorded to cost of product when inventory is determined to be in excess of anticipated demand or considered obsolete. At the point of loss recognition, a new, lower-cost basis for that inventory is established, and subsequent changes in facts and circumstances do not result in the restoration or increase in the newly established cost basis. Property and Equipment Property and equipment are recorded at cost less accumulated depreciation. Depreciation is calculated using the straight-line method, over the estimated useful lives of the following assets: Estimated Useful Life (years) Computers, equipment, and software 1.5 to 7 Furniture and fixtures 5 to 7 Building and building improvements 7 to 40 Land improvements 10 to 40 Leasehold improvements Lease term, not to exceed 10 years Construction in progress is related to the construction or development of property and equipment that have not yet been placed in service for their intended use. Goodwill and Other Long-Lived Assets Goodwill represents the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recorded. The excess of the purchase price over the estimated fair value of net assets of businesses acquired in a business combination is recognized as goodwill. Goodwill is tested for impairment annually during the fourth quarter or more frequently if certain circumstances indicate the carrying value of goodwill is impaired. A qualitative assessment is first made to determine whether it is necessary to quantitatively test goodwill for impairment. This initial assessment includes, among others, consideration of macroeconomic conditions and financial performance. If the qualitative assessment indicates that it is more likely than not that an impairment exists, a quantitative analysis is performed by determining the fair value of each reporting unit using a combination of the income approach and the market approach. Based on the outcome of the quantitative assessments, the Company compares the estimated fair value of each reporting unit with their respective carrying values, including goodwill. An impairment loss is recognized to the extent that the carrying amount of goodwill exceeds the asset's implied fair value. Other intangible assets acquired in a business combination related to in-process research and development ("IPR&D") projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. Indefinite-lived intangibles are not amortized into the results of operations but instead are evaluated for impairment. If and when development is complete, the associated assets would be deemed finite-lived and would be amortized as cost of revenues over their respective estimated useful lives at that point in time. If the research and development project is abandoned, the acquired IPR&D assets are written off and charged to expense in the period of abandonment. Long-lived assets, such as property, plant, and equipment, and purchased intangible assets subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset, or asset group, to estimated undiscounted future cash flows expected to be generated by the asset, or asset group. An impairment charge is recognized by the amount by which the carrying amount of the asset, or asset group, exceeds its fair value. The Company amortizes intangible assets with estimable useful lives on a straight-line basis over their useful lives. Revenue Recognition 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 by following a five-step process, (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price, and (5) recognize revenue when or as the Company satisfies a performance obligation, as further described below. Identify the contract with a customer . The Company generally considers a sales contract or agreement with an approved purchase order as a customer contract provided that collection is considered probable, which is assessed based on the creditworthiness of the customer as determined by credit checks, payment histories, and/or other circumstances. The Company combines contracts with a customer if contracts are negotiated with a single commercial substance or contain price dependencies. Identify the performance obligations in the contract . Product performance obligations include hardware and software licenses and service performance obligations include maintenance, software post-contract support, training, and professional services. Certain software licenses and related post-contract support are combined into a single performance obligation when the maintenance updates are critical to the continued functionality of the software. Determine the transaction price . The transaction price for the Company’s contracts with its customers consists of both fixed and variable consideration provided it is probable that a significant reversal of revenue will not occur when the uncertainty related to variable consideration is resolved. Fixed consideration includes amounts to be contractually billed to the customer while variable consideration includes estimates for rights of return, rebates, and price protection, which are based on historical sales returns and price protection credits, specific criteria outlined in rebate agreements, and other factors known at the time. The Company generally invoices customers for hardware, software licenses and related maintenance arrangements at time of delivery, and professional services either upfront or upon meeting certain milestones. Customer invoices are generally due within 30 to 90 days after issuance. The Company’s contracts with customers typically do not include significant financing components as the period between the transfer of performance obligations and timing of payment are generally within one year. Allocate the transaction price to the performance obligations in the contract . For contracts that contain multiple performance obligations, the Company allocates the transaction price to the performance obligations on a relative standalone selling price basis. Standalone selling prices are based on multiple factors including, but not limited to historical discounting trends for products and services, pricing practices in different geographies and through different sales channels, gross margin objectives, internal costs, competitor pricing strategies, and industry technology lifecycles. Recognize revenue when or as the Company satisfies a performance obligation . Revenue for hardware and certain software licenses, are recognized at a point in time, which is generally upon shipment or delivery. Certain software licenses combined with post-contract support are recognized over time on a ratable basis over the term of the license. Revenue for maintenance and software post-contract support is recognized over time on a ratable basis over the contract term. Revenue from training and professional services is recognized over time as services are completed or ratably over the contractual period of generally one year or less. Deferred Commissions Sales commissions earned by the Company’s sales force are considered incremental and recoverable costs of obtaining a contract with a customer. These costs are deferred and then amortized over a period of benefit which is typically over the term of the customer contracts as initial commission rates and renewal rates are the same. Amortization expense is included in sales and marketing expenses in the accompanying Consolidated Statements of Operations. Allowance for Doubtful Accounts The allowance for doubtful accounts is based on the Company's assessment of the collectability of customer accounts. The Company regularly reviews its receivables that remain outstanding past their applicable payment terms and establishes an allowance by considering factors such as historical experience, credit quality, and age of the accounts receivable balances, and current economic conditions that may affect a customer's ability to pay. Warranty Reserves The Company generally offers a one -year warranty on most of its hardware products, and a 90 -day warranty on the media that contains the software embedded in the products. Warranty costs are recognized as part of the Company's cost of sales based on associated material costs, logistics costs, labor costs, and overhead at the time revenue is recognized. Material costs are estimated primarily based upon the historical costs to repair or replace product returns within the warranty period. Labor, logistics and overhead costs are estimated primarily based upon historical trends in the cost to support customer cases within the warranty period. Contract Manufacturer Liabilities The Company establishes a liability for non-cancelable, non-returnable purchase commitments with its contract manufacturers for carrying charges, quantities in excess of its demand forecasts, or obsolete material charges for components purchased by the contract manufacturers to meet the Company’s demand forecast or customer orders. The demand forecasts are based upon historical trends and analysis from the Company's sales and marketing organizations, adjusted for overall market conditions. Research and Development Costs to research, design, and develop the Company's products are expensed as incurred. Software Development Costs Capitalization of software development costs for software to be sold, leased, or otherwise marketed begins when a product's technological feasibility has been established and ends when a product is available for general release to customers. Generally, the Company's products are released soon after technological feasibility has been established. As a result, costs incurred between achieving technological feasibility and product general availability have not been significant. The Company capitalizes costs associated with internal-use software systems during the application development stage. Such capitalized costs include external direct costs incurred in developing or obtaining the applications and payroll and payroll-related costs for employees, who are directly associated with the development of the applications. Advertising Advertising costs are charged to sales and marketing expense as incurred. Advertising expense was $20.0 million , $19.9 million , and $15.8 million , for 2018 , 2017 , and 2016 , respectively. Foreign Currency Assets and liabilities of foreign operations with non-U.S. Dollar functional currency are translated to U.S. Dollars using exchange rates in effect at the end of the period. Revenue and expenses are translated to U.S. Dollars using rates that approximate those in effect during the period. The resulting translation adjustments are included in the Company’s Consolidated Balance Sheets in the stockholders’ equity section as a component of accumulated other comprehensive loss. The Company records foreign exchange transaction gains and losses for assets and liabilities denominated in non-functional currencies. These remeasurement adjustments are recorded in other expense, net in the Consolidated Statements of Operations. Loss Contingencies The Company is subject to the possibility of various loss contingencies arising in the ordinary course of business. Management considers the likelihood of loss related to an asset, or the incurrence of a liability, as well as its ability to reasonably estimate the amount of loss, in determining loss contingencies. An estimated loss contingency is accrued when it is probable that an asset has been impaired or a liability has been incurred and the amount of loss can be reasonably estimated. The Company regularly evaluates current information available to determine whether such accruals should be adjusted and whether new accruals are required. Share-Based Compensation The Company measures and recognizes compensation cost for all share-based awards made to employees and directors, including employee stock options, restricted stock awards ("RSAs"), restricted stock units ("RSUs"), performance share awards ("PSAs") and employee stock purchases related to the Employee Stock Purchase Plan ("ESPP"). For service condition only awards, share-based compensation expense is based on the fair value of the underlying awards and amortized on a straight-line basis. For PSAs and market-based RSUs, share-based compensation expense is amortized on a straight-line basis for each separate vesting portion of the awards. The Company accounts for forfeitures as they occur. The Company utilizes the Black-Scholes-Merton (“BSM”) option-pricing model to estimate the fair value of its ESPP purchase rights. The BSM model requires various highly subjective assumptions that represent management's best estimates of volatility, risk-free interest rate, expected life, and dividend yield. The Company estimates expected volatility based on the implied volatility of market-traded options, on the Company's common stock, adjusted for other relevant factors including historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected life of the Company’s ESPP. The expected life of ESPP purchase rights approximates the offering period. The Company determines the grant date fair value of its RSUs, RSAs, and PSAs based on the closing market price of the Company’s common stock on the date of grant, adjusted by the present value of the 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. For market-based RSUs, the Company estimates the fair value and derived service period using the Monte Carlo simulation option pricing model ("Monte Carlo model"). The determination of the grant date fair value and derived service periods using the Monte Carlo model is affected by the Company's stock price, comparative market-based returns, as well as various highly subjective assumptions that represent management's best estimates of volatility, risk-free interest rate, and dividend yield. The Company estimates expected volatility based on the implied volatility of market-traded options, on the Company's common stock, adjusted for other relevant factors including historical volatility of the Company’s common stock over the contractual life of the Company's market-based RSUs. Provision for Income Taxes Deferred tax assets and liabilities are recognized for the expected tax consequences of temporary differences between the tax bases of assets and liabilities and their reported amounts. Valuation allowances are recorded to reduce deferred tax assets to the amount that will more likely than not be realized. The Company accounts for uncertainty in income taxes using a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon settlement. The Company classifies the liability for unrecognized tax benefits as current to the extent that the Company anticipates payment (or receipt) of cash within one year . Interest and penalties related to uncertain tax positions are recognized in the provision for income taxes. Concentrations of Risk Financial instruments that subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, investments, derivatives, and accounts receivable. The Company invests only in high-quality credit instruments and maintains its cash, cash equivalents and available-for-sale investments in fixed income securities with several high-quality institutions. Deposits held with banks, including those held in foreign branches of global banks, may exceed the amount of insurance provided on such deposits. We mitigate the concentration of credit risk in our investment portfolio through diversification of the investments in various industries and asset classes, and limits to the amount of credit exposure to any single issuer and credit rating. The Company’s derivatives expose it to credit risk to the extent that counterparties may be unable to meet the terms of the agreement. To mitigate concentration of risk related to its derivatives, the Company establishes counterparty limits to major credit-worthy financial institutions. In addition, the potential risk of loss with any one counterparty resulting from this type of credit risk is monitored and the derivatives transacted with these entities are relatively short in duration. Therefore, the Company does not expect material losses as a result of defaults by counterparties. Generally, credit risk with respect to accounts receivable is diversified due to the number of entities comprising the Company's customer base and their dispersion across different geographic locations throughout the world. The Company performs ongoing credit evaluations of its customers and generally does not require collateral on accounts receivable. During the years ended December 31, 2018 , 2017 , and 2016 , no single customer accounted for 10% or more of net revenues. The Company relies on sole suppliers for certain of its components such as application-specific integrated circuits ("ASICs") and custom sheet metal. Additionally, the Company relies primarily on a limited number of significant independent contract manufacturers and original design manufacturers for the production of its products. The inability of any supplier or manufacturer to fulfill supply requirements of the Company could negatively impact future operating results. Recently Adopted Accounting Standard Comprehensive Income: Effective January 1, 2018, the Company early adopted FASB ASU No. 2018-02 (Topic 220), Income Statement - Reporting Comprehensive Income , issued in February 2018, with an election to reclassify stranded tax effects resulting from the U.S. Tax Cuts and Jobs Act (the "Tax Act"), from accumulated other comprehensive income to retained earnings. The adoption resulted in a reclassification of $5.7 million in income from accumulated other comprehensive loss to accumulated deficit as of the adoption date. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. Financial Instruments: On January 1, 2018, the Company adopted FASB ASU No. 2016-01, Financial Instruments—Overall: Recognition and Measurement of Financial Assets and Financial Liabilities and FASB ASU No. 2018-03, Technical Corrections and Improvements to Financial Instruments - Overall , which changes how entities classify and 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. The Company adopted ASU 2016-01 as of January 1, 2018 using the modified retrospective method for its equity securities with readily determinable fair values and the prospective method for its equity securities without readily determinable fair values, resulting in no impact to the opening accumulated deficit balance. The Company has elected to use the measurement alternative for its equity investments without readily determinable fair value, defined as cost adjusted for changes from observable transactions for identical or similar investments of the same issuer, less impairment. See Note 4, Cash Equivalents and Investments for additional disclosures required upon adopting the standard. Revenue Recognition: On January 1, 2018, the Company adopted FASB ASU No. 2014-09 (Topic 606) - Revenue from Contracts with Customers (“ASU 2014-09” or "Topic 606"), which provides guidance for revenue recognition that superseded the revenue recognition requirements in Accounting Standards Codification ("ASC") Topic 605, Revenue Recognition ("Topic 605") and most industry specific guidance. Under ASU 2014-09, 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. The Company adopted ASU 2014-09 under the modified retrospective approach, applying the amendments to prospective reporting periods. Results for reporting periods beginning after January 1, 2018 are presented under Topic 606, while prior period amounts are not adjusted and continue to be reported in accordance with the historic accounting under Topic 605. The cumulative effect of the changes made to the Company's Consolidated Balance Sheet as of January 1, 2018 for the adoption of Topic 606 to all contracts with customers that were not completed as of December 31, 2017 was recorded as an adjustment to accumulated deficit as of the adoption date as follows: December 31, 2017 January 1, 2018 As reported Adjustments As adjusted Assets: Accounts receivable, net of allowances $ 852.0 $ (1.9 ) $ 850.1 Prepaid expenses and other current assets 299.9 31.5 331.4 Other long-term assets 415.5 (21.1 ) 394.4 Total assets $ 9,833.8 $ 8.5 $ 9,842.3 Liabilities: Deferred revenue $ 1,030.3 $ (225.4 ) $ 804.9 Other accrued liabilities 304.3 33.8 338.1 Long-term deferred revenue 509.0 (124.6 ) 384.4 Total liabilities $ 5,152.9 $ (316.2 ) $ 4,836.7 Stockholders' Equity: Accumulated deficit $ (3,355.8 ) $ 324.7 $ (3,031.1 ) Upon adoption, the Company recorded a cumulative effect adjustment of $324.7 million , net of tax adjustment of $63.9 million , which decreased the January 1, 2018 opening accumulated deficit balance on the Consolidated Balance Sheet, primarily as a result of the following items: • Distributor Sales : Under Topic 606, the Company recognizes revenue from sales to distributors upon delivery of the product to the distributor, rather than upon delivery of the product to the end-customer. Rebates and incentives offered to distributors, which are earned when sales to end-customers are completed, are estimated at the point of revenue recognition. • Software Revenue : Under Topic 605, the Company deferred revenue for software licenses where vendor-specific objective evidence of fair value had not been established for undelivered items (primaril

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Business Combinations	Business Combinations The Company's Consolidated Financial Statements include the operating results of acquired businesses from the date of each acquisition. Pro forma results of operations for these acquisitions have not been presented as the financial impact to the Company's consolidated results of operations, both individually and in aggregate, 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 and residual goodwill. The Company acquired HTBase Corporation ("HTBase") in 2018; Cyphort Inc. ("Cyphort") in 2017; and AppFormix, Inc. ("AppFormix"), Aurrion, Inc. ("Aurrion"), and BTI Systems Inc. (“BTI”) in 2016. The following table summarizes the fair values of the assets acquired and liabilities assumed at the acquisition dates (in millions): 2018 2017 2016 HTBase (1) Cyphort (2) AppFormix Aurrion BTI (2) Net tangible assets acquired/(liabilities) assumed $ (1.0 ) $ 1.4 $ (5.3 ) $ 6.0 $ (19.7 ) Intangible assets 7.8 15.4 20.3 49.0 43.3 Goodwill (3) 14.4 16.7 32.9 46.9 20.2 Total $ 21.2 $ 33.5 $ 47.9 $ 101.9 $ 43.8 ________________________________ (1) The primary areas of the preliminary purchase price allocation that are subject to change relate to certain legal and income tax matters. (2) See Note 7, Goodwill and Purchased Intangible Assets , for adjustments made during the measurement period subsequent to the acquisition dates. (3) The goodwill recognized for these acquisitions was primarily attributable to expected synergies and is not deductible for U.S. federal income tax purposes. The following table summarizes the fair value of the separately identifiable intangible assets at the time of acquisition and the period over which each intangible asset will be amortized (in millions, except years): 2018 2017 2016 HTBase Cyphort AppFormix Aurrion BTI Weighted Amount Weighted Amount Weighted Average Estimated Useful Life (In Years) Amount Weighted Average Estimated Useful Life (In Years) Amount Weighted Average Estimated Useful Life (In Years) Amount Finite-lived intangible assets: Existing technology 4 $ 7.8 5 $ 15.4 5 $ 20.1 — $ — 8 $ 37.1 Customer relationships — — — — 1 0.2 — — 8 5.3 Other — — — — — — — — 1 0.9 Total intangible assets with finite lives 7.8 15.4 20.3 — 43.3 Indefinite-lived intangible assets: IPR&D — — — 49.0 — Total intangible assets acquired $ 7.8 $ 15.4 $ 20.3 $ 49.0 $ 43.3 2018 Acquisition HTBase On December 7, 2018 , the Company acquired 100% of the equity of HTBase for $19.6 million of cash. The acquisition of HTBase, a software company that has developed a unique and disruptive platform for software-defined enterprise multicloud, is expected to accelerate Juniper's leadership in multicloud and function with the compute orchestration capabilities of Contrail Enterprise Multicloud. Prior to the acquisition, the Company had an outstanding promissory note and bridge notes totaling $1.6 million , measured at fair value, which were effectively settled upon acquisition. Under the terms of the acquisition agreement with HTBase, the Company granted certain share-based awards to continuing employees in substitution of awards held by such 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. 2017 Acquisition Cyphort On September 18, 2017 , the Company acquired 100% of 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. 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. 2016 Acquisitions AppFormix On December 6, 2016, the Company acquired 100% of AppFormix for $47.9 million of cash. AppFormix was a company focused on cloud infrastructure optimization software. The Company acquired AppFormix on the expectation that it would complement the analytics and capabilities of Contrail and help its customers enhance their cloud operations. Under the terms of the acquisition agreement, the Company assumed share-based awards for continuing employees from the acquisition of AppFormix, which were granted in contemplation of future services. The fair value of these share-based awards was $23.9 million , which will be expensed as share-based compensation over the remaining service period. Aurrion On August 9, 2016, the Company acquired the remaining ownership interest in Aurrion, increasing its ownership from 18% to 100% , for $74.3 million of cash. Aurrion, was a privately-held provider of fabless silicon photonic technology. The Company acquired Aurrion on the expectation that it would strengthen the Company's long-term competitive advantage in cost-effective, high-density, high-speed networks. Prior to the acquisition, the Company had a pre-existing investment in Aurrion's equity and also held convertible debt that were remeasured to fair value of $17.2 million and $10.4 million , respectively, based upon the perspective of a market participant when estimating the fair value. Under the terms of the acquisition agreement, the Company assumed share-based awards for continuing employees from the acquisition of Aurrion, which were granted in contemplation of future services. The fair value of these share-based awards was $55.0 million , which will be expensed as share-based compensation over the remaining service period. Additionally, the Company acquired IPR&D consisting of existing research and development projects that had not yet reached technological feasibility at the time of the acquisition. The acquired IPR&D involves technology for cost-effective, high-speed networks. The IPR&D was valued using the multi-period excess earnings method under the income approach by discounting forecasted cash flows directly related to the products expected to result from the associated project. BTI On April 1, 2016, the Company acquired the remaining ownership interest in BTI, increasing its ownership from 12% to 100% , for $25.8 million of cash. BTI was a privately-held provider of cloud and metro networking systems and software to content, cloud, and service providers. The Company acquired BTI on the expectation that this would help to accelerate the Company's ability to deliver open and automated packet optical transport solutions. Prior to the acquisition, the Company had a pre-existing investment in BTI's equity and remeasured the investment to its fair value of $17.1 million , which was based upon the perspective of a market participant when estimating the fair value. The Company also held $0.9 million of convertible debt measured at fair value and settled upon acquisition. The Company also repaid upon acquisition $18.6 million of certain outstanding BTI liabilities assumed. Additionally, under the terms of the acquisition agreement, the Company assumed share-based awards for continuing employees from the acquisition of BTI, which were granted in contemplation of future services. The fair value of these share-based awards was $8.6 million , which will be expensed as share-based compensation over the remaining service period. Acquisition Costs The Company recognized $4.4 million , $2.1 million , and $11.8 million of acquisition-related costs during the years ended December 31, 2018 , December 31, 2017 , and December 31, 2016 , respectively. These acquisition-related costs were expensed in the period incurred within general and administrative expense in the Company's Consolidated Statements of Operations.

Cash Equivalents and Investment

Cash Equivalents and Investments	12 Months Ended
	Dec. 31, 2018
Cash Equivalents and Investments [Abstract]
Cash Equivalents and Investments	Cash Equivalents and Investments Investments in Available-for-Sale Debt Securities The following table summarizes the Company's unrealized gains and losses and fair value of investments designated as available-for-sale debt securities as of December 31, 2018 and December 31, 2017 (in millions): As of December 31, 2018 As of December 31, 2017 Amortized Gross Unrealized Gross Unrealized Estimated Fair Amortized Gross Unrealized Gross Unrealized Estimated Fair Fixed income securities: Asset-backed securities $ 46.8 $ — $ (0.3 ) $ 46.5 $ 287.1 $ — $ (0.6 ) $ 286.5 Certificates of deposit 152.9 — — 152.9 83.8 — — 83.8 Commercial paper 393.6 — — 393.6 217.1 — — 217.1 Corporate debt securities 416.1 — (3.1 ) 413.0 929.6 0.4 (3.0 ) 927.0 Foreign government debt securities 20.0 — (0.1 ) 19.9 62.9 — (0.2 ) 62.7 Time deposits 278.6 — — 278.6 239.2 — — 239.2 U.S. government agency securities 87.2 — (0.2 ) 87.0 143.9 — (0.7 ) 143.2 U.S. government securities 811.8 — (0.5 ) 811.3 406.8 0.1 (0.9 ) 406.0 Total fixed income securities 2,207.0 — (4.2 ) 2,202.8 2,370.4 0.5 (5.4 ) 2,365.5 Privately-held debt and redeemable preferred stock securities 16.6 37.4 — 54.0 15.9 37.4 — 53.3 Total available-for-sale debt securities $ 2,223.6 $ 37.4 $ (4.2 ) $ 2,256.8 $ 2,386.3 $ 37.9 $ (5.4 ) $ 2,418.8 Reported as: Cash equivalents $ 936.5 $ — $ — $ 936.5 $ 351.0 $ — $ — $ 351.0 Short-term investments 1,069.2 — (1.9 ) 1,067.3 1,027.2 0.1 (1.2 ) 1,026.1 Long-term investments 201.3 — (2.3 ) 199.0 992.2 0.4 (4.2 ) 988.4 Other long-term assets 16.6 37.4 — 54.0 15.9 37.4 — 53.3 Total $ 2,223.6 $ 37.4 $ (4.2 ) $ 2,256.8 $ 2,386.3 $ 37.9 $ (5.4 ) $ 2,418.8 The following table presents the contractual maturities of the Company's total fixed income securities as of December 31, 2018 (in millions): Amortized Cost Estimated Fair Value Due in less than one year $ 2,005.7 $ 2,003.8 Due between one and five years 201.3 199.0 Total $ 2,207.0 $ 2,202.8 The following tables present the Company's total fixed income securities that were in an unrealized loss position as of December 31, 2018 and December 31, 2017 (in millions): As of December 31, 2018 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 $ 3.1 $ — $ 43 $ (0.3 ) $ 46.1 $ (0.3 ) Corporate debt securities 72.6 (0.1 ) 330.7 (3.0 ) 403.3 (3.1 ) Foreign government debt securities 1.5 — 18.4 (0.1 ) 19.9 (0.1 ) U.S. government agency securities 2.0 — 45.2 (0.2 ) 47.2 (0.2 ) U.S. government securities 344.0 — 63.5 (0.5 ) 407.5 (0.5 ) Total fixed income securities $ 423.2 $ (0.1 ) $ 500.8 $ (4.1 ) $ 924.0 $ (4.2 ) As of December 31, 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 $ 215.2 $ (0.4 ) $ 38.4 $ (0.2 ) $ 253.6 $ (0.6 ) Corporate debt securities 646.7 (2.1 ) 108.6 (0.9 ) 755.3 (3.0 ) Foreign government debt securities 47.3 (0.2 ) 6.6 — 53.9 (0.2 ) U.S. government agency securities 68.3 (0.2 ) 67.9 (0.5 ) 136.2 (0.7 ) U.S. government securities 260.8 (0.7 ) 51.8 (0.2 ) 312.6 (0.9 ) Total fixed income securities $ 1,238.3 $ (3.6 ) $ 273.3 $ (1.8 ) $ 1,511.6 $ (5.4 ) As of December 31, 2018 , the Company had 490 investments in unrealized loss positions. The gross unrealized losses related to these investments were primarily due to changes in market interest rates. The Company does not intend to sell these investments and does not believe that it is more likely than not it will be required to sell any of these investments before recovery of the entire amortized cost basis, therefore the Company has determined that no other-than-temporary impairments associated with credit losses were required to be recognized during the years ended December 31, 2018 , 2017 , and 2016 . During the years ended December 31, 2018 , 2017 , and 2016 , there were no material gross realized gains or losses from available-for-sale debt securities. Investments in Equity Securities The following table presents the Company's investments in equity securities as of December 31, 2018 and 2017 (in millions): As of December 31, 2018 2017 Equity investments with readily determinable fair value Money market funds (1) $ 996.9 $ 969.8 Mutual funds (2) 24.3 27.6 Publicly-traded equity securities 2.8 — Equity investments without readily determinable fair value (3) 36.4 29.7 Total equity securities $ 1,060.4 $ 1,027.1 Reported as: Cash equivalents $ 985.3 $ 928.0 Short-term investments 2.8 — Prepaid expenses and other current assets 10.9 36.3 Other long-term assets 61.4 62.8 Total $ 1,060.4 $ 1,027.1 ________________________________ (1) Prior to January 1, 2018, money market funds were classified as available-for-sale securities and accounted for at fair value with unrealized gains and losses recognized in accumulated other comprehensive income (loss). Realized gains or losses from sales or impairments were recognized in the Consolidated Statements of Operations. (2) Prior to January 1, 2018, mutual funds related to the Company's NQDC plan were classified as trading securities. Unrealized gains or losses were recognized in the Consolidated Statements of Operations. (3) Prior to January 1, 2018, certain investments in privately-held companies were accounted for at cost less impairment. Realized gains or losses from sales or impairments were recognized in the Consolidated Statements of Operations. During the year ended December 31, 2018, there were $3.2 million in unrealized losses recognized for equity investments. During the years ended 2017 , and 2016 , there were no material unrealized gains or losses recognized for equity investments. Restricted Cash and Investments The Company has restricted cash and investments for: (i) amounts held in escrow accounts, as required in connection with certain acquisitions completed primarily between 2015 and 2018; (ii) amounts held under the Company's short-term disability plan in California; and (iii) amounts under the NQDC plan for senior-level employees. Restricted investments are designated as equity investments. As of December 31, 2018 , the carrying value of restricted cash and investments was $52.7 million , of which $27.6 million was included in prepaid expenses and other current assets and $25.1 million was included in other long-term assets on the Consolidated Balance Sheets. The following table provides a reconciliation of cash, cash equivalents, and restricted cash included in the Consolidated Balance Sheets as of December 31, 2018 and December 31, 2017 (in millions): As of December 31, 2018 2017 Cash and cash equivalents $ 2,489.0 $ 2,006.5 Restricted cash included in Prepaid expenses and other current assets 16.8 49.6 Restricted cash included in Other long-term assets — 3.0 Total cash, cash equivalents, and restricted cash $ 2,505.8 $ 2,059.1

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
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 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 debt securities: Asset-backed securities $ — $ 46.5 $ — $ 46.5 $ — $ 286.5 $ — $ 286.5 Certificates of deposit — 152.9 — 152.9 — 83.8 — 83.8 Commercial paper — 393.6 — 393.6 — 217.1 — 217.1 Corporate debt securities — 413.0 — 413.0 — 927.0 — 927.0 Foreign government debt securities — 19.9 — 19.9 — 62.7 — 62.7 Time deposits — 278.6 — 278.6 — 239.2 — 239.2 U.S. government agency securities — 87.0 — 87.0 — 143.2 — 143.2 U.S. government securities 352.8 458.5 — 811.3 322.4 83.6 — 406.0 Privately-held debt and redeemable preferred stock securities — — 54.0 54.0 — — 53.3 53.3 Total available-for-sale debt securities 352.8 1,850.0 54.0 2,256.8 322.4 2,043.1 53.3 2,418.8 Equity securities: Money market funds (1) 996.9 — — 996.9 969.8 — — 969.8 Mutual funds (2) 24.3 — — 24.3 27.6 — — 27.6 Publicly-traded equity securities 2.8 — — 2.8 — — — — Total equity securities 1,024.0 — — 1,024.0 997.4 — — 997.4 Derivative assets: Foreign exchange contracts — 5.3 — 5.3 — 9.2 — 9.2 Total assets measured at fair value $ 1,376.8 $ 1,855.3 $ 54.0 $ 3,286.1 $ 1,319.8 $ 2,052.3 $ 53.3 $ 3,425.4 Liabilities: Derivative liabilities: Foreign exchange contracts $ — $ (7.1 ) $ — $ (7.1 ) $ — $ (1.8 ) $ — $ (1.8 ) Total liabilities measured at fair value $ — $ (7.1 ) $ — $ (7.1 ) $ — $ (1.8 ) $ — $ (1.8 ) Total assets, reported as: Cash equivalents $ 1,025.2 $ 896.6 $ — $ 1,921.8 $ 928.1 $ 350.9 $ — $ 1,279.0 Short-term investments 297.5 772.6 — 1,070.1 247.5 778.6 — 1,026.1 Long-term investments 18.2 180.8 — 199.0 74.8 913.6 — 988.4 Prepaid expenses and other current assets 10.8 5.3 — 16.1 36.3 9.2 — 45.5 Other long-term assets 25.1 — 54.0 79.1 33.1 — 53.3 86.4 Total assets measured at fair value $ 1,376.8 $ 1,855.3 $ 54.0 $ 3,286.1 $ 1,319.8 $ 2,052.3 $ 53.3 $ 3,425.4 Total liabilities, reported as: Other accrued liabilities $ — $ (7.1 ) $ — $ (7.1 ) $ — $ (1.8 ) $ — $ (1.8 ) Total liabilities measured at fair value $ — $ (7.1 ) $ — $ (7.1 ) $ — $ (1.8 ) $ — $ (1.8 ) ________________________________ (1) Balance includes $11.6 million and $16.8 million in restricted investments measured at fair value, related to the Company's acquisition-related escrows for the years ended December 31, 2018 and 2017 , respectively. The December 31, 2017 balance also includes $25.0 million related to the Company's Directors and Officers indemnification trust, which was subsequently terminated. (2) Balance relates to restricted investments measured at fair value related to the Company's NQDC plan. The Company's Level 2 available-for-sale debt 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 years ended December 31, 2018 and 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 year ended December 31, 2018 , there were no significant activities related to privately-held debt and redeemable preferred stock, other than the notes settled upon acquisition of HTBase. See Note 3, Business Combinations , for further information. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Certain of the Company's assets, including intangible assets and goodwill, are measured at fair value on a nonrecurring basis, when they are deemed to be other-than temporarily impaired. There were no impairment charges recognized during the years ended December 31, 2018 , 2017, and 2016. Equity investments without readily determinable fair value are measured at fair value, when they are deemed to be impaired or when there is an adjustment from observable price changes. For the year ended December 31, 2018 , there were no material impairment charges or adjustments resulting from observable price changes for equity investments without readily determinable fair value. As of December 31, 2018 and 2017 , the Company had no liabilities 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 December 31, 2018 and December 31, 2017 , the estimated fair value of the Company's total outstanding debt in the Consolidated Balance Sheets was $2,158.7 million and $2,252.9 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"), along with the accumulated interest paid in kind, of $69.0 million and $61.2 million approximates its fair value as of December 31, 2018 and December 31, 2017 , respectively. Notes receivable are generally classified as Level 3 asset due to the lack of observable inputs to determine fair value. The carrying value of a contract manufacturer deposit of $23.9 million and long-term trade accounts receivable of $15.0 million , reported within other long-term assets in the Consolidated Balance Sheets approximates its fair value as of December 31, 2018 . See Note 8, Other Financial Information, for further information on the Pulse Note and contract manufacturer deposit.

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments The notional amount of the Company's foreign currency derivatives is summarized as follows (in millions): As of December 31, 2018 2017 Cash flow hedges $ 497.7 $ 521.1 Non-designated derivatives 158.7 108.3 Total $ 656.4 $ 629.4 Cash Flow Hedges The Company uses foreign currency forward contracts to hedge the Company's planned cost of revenues and operating expenses denominated in foreign currencies. These derivatives are designated as cash flow hedges. Cash flow hedge derivatives typically have maturities of seventeen months or less. As of December 31, 2018 , an estimated $1.6 million of unrealized net loss within accumulated other comprehensive loss is expected to be reclassified into earnings within the next twelve months. The Company recognized an unrealized loss of $8.7 million , an unrealized gain of $20.2 million , and an unrealized loss of $1.3 million in accumulated other comprehensive loss for the effective portion of its derivative instruments during the years ended December 31, 2018 , 2017 , and 2016 , respectively. The Company reclassified gains of $0.9 million , $7.6 million , and $1.8 million out of accumulated other comprehensive loss to cost of revenues and operating expenses in the Consolidated Statement of Operations during the years ended December 31, 2018 , 2017 , and 2016 , respectively. The ineffective portion of the Company's derivative instruments recognized in its Consolidated Statements of Operations was not material during the years ended December 31, 2018 , 2017 , and 2016 , respectively. See Note 5, Fair Value Measurements, for the fair values of the Company’s derivative instruments in the 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 to three months . 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 Consolidated Statements of Operations were $7.6 million , $1.8 million and $0.5 million during the years ended December 31, 2018 , 2017 , and 2016 , respectively. See Note 2, Significant Accounting Policies, for the Company’s policy regarding the offsetting of derivative assets and derivative liabilities.

Goodwill and Purchased Intangib

Goodwill and Purchased Intangible Assets	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Purchased Intangible Assets	Goodwill and Purchased Intangible Assets Goodwill The Company's goodwill activity was as follows (in millions): Total December 31, 2016 $ 3,081.7 Additions due to business combination 16.7 Other (*) (2.2 ) December 31, 2017 3,096.2 Additions due to business combination 14.4 Other (*) (1.8 ) December 31, 2018 $ 3,108.8 ________________________________ (*) Other primarily consists of certain purchase accounting adjustments related to the acquisitions of BTI and Cyphort. In the fourth quarter of 2018, the Company performed its annual goodwill impairment test for the Company's three reporting units: Routing, Switching, and Security. There was no goodwill impairment during the years ended December 31, 2018, 2017 and 2016. Purchased Intangible Assets The Company’s purchased intangible assets, net, were as follows (in millions): As of December 31, 2018 As of December 31, 2017 Gross Accumulated Accumulated Impairments and Net Gross Accumulated Accumulated Impairments and Net Finite-lived intangible assets: Technologies and patents $ 648.1 $ (534.0 ) $ (49.9 ) $ 64.2 $ 640.3 $ (518.1 ) $ (49.9 ) $ 72.3 Customer contracts, support agreements, and related relationships 83.6 (75.5 ) (2.8 ) 5.3 83.6 (74.1 ) (2.8 ) 6.7 Other 2.0 (2.0 ) — — 2.0 (1.9 ) — 0.1 Total 733.7 (611.5 ) (52.7 ) 69.5 725.9 (594.1 ) (52.7 ) 79.1 Indefinite-lived intangible assets: IPR&D 49.0 — — 49.0 49.0 — — 49.0 Total purchased intangible assets $ 782.7 $ (611.5 ) $ (52.7 ) $ 118.5 $ 774.9 $ (594.1 ) $ (52.7 ) $ 128.1 Amortization expense was $17.4 million , $17.5 million , and $16.3 million for the years ended December 31, 2018 , 2017 , and 2016 , respectively. There were no impairment charges related to purchased intangible assets during the years ended December 31, 2018 , 2017 , and 2016 . As of December 31, 2018 , the estimated future amortization expense of purchased intangible assets with finite lives is as follows (in millions): Years Ending December 31, Amount 2019 $ 25.1 2020 17.2 2021 12.9 2022 7.7 2023 5.3 Thereafter 1.3 Total $ 69.5

Other Financial Information

Other Financial Information	12 Months Ended
	Dec. 31, 2018
Other Financial Information [Abstract]
Other Financial Information	Other Financial Information Inventory The majority of the Company's inventory is production components to be used in the manufacturing process, and finished goods inventory in transit. In addition, the Company purchases and holds inventory to provide adequate component supplies over the life of the underlying products. Total inventory consisted of the following (in millions): As of December 31, 2018 2017 Production and service materials $ 60.6 $ 71.2 Finished goods 21.4 26.6 Inventory $ 82.0 $ 97.8 Reported as: Prepaid expenses and other current assets $ 80.6 $ 93.8 Other long-term assets 1.4 4.0 Total $ 82.0 $ 97.8 Property and Equipment, Net Property and equipment, net, consisted of the following (in millions): As of December 31, 2018 2017 Computers and equipment $ 1,100.0 $ 1,151.7 Software 223.3 217.8 Leasehold improvements 235.2 258.6 Furniture and fixtures 48.6 47.9 Building and building improvements 254.3 252.8 Land and land improvements 243.2 241.0 Construction-in-process 19.5 53.5 Property and equipment, gross 2,124.1 2,223.3 Accumulated depreciation (1,172.4 ) (1,202.2 ) Property and equipment, net $ 951.7 $ 1,021.1 Depreciation expense was $193.2 million , $202.8 million , and $184.5 million in 2018 , 2017 , and 2016 , respectively. Notes Receivable and Deposit Total outstanding notes receivable and deposit, net of issuance costs, reported within other long-term assets in the Consolidated Balance Sheets were as follows (in millions): As of December 31, 2018 2017 Pulse Note (including accumulated interest paid in kind) $ 69.0 $ 61.2 Contract manufacturer deposit (non-interest bearing) 23.9 — Total $ 92.9 $ 61.2 In connection with the sale of its Junos Pulse product portfolio in 2014, the Company was issued a non-contingent interest-bearing promissory note of $125.0 million . In 2017, the Company received payment of $75.0 million and the outstanding interest due. The maturity date of the Pulse Note was extended to September 30, 2022 under the terms of an amended agreement. The amended agreement also provided that interest due on the note be paid in kind by increasing the principal amount and interest rate on the Pulse Note. The outstanding balance of the Pulse Note was classified as a long-term asset based on expected collection beyond twelve months from the Consolidated Balance Sheet date. In 2018, the Company paid a deposit of $25.0 million to a contract manufacturer in exchange for improved pricing and savings on inventory carrying charges. The deposit was recorded at the face value of $25.0 million , less an unamortized discount of $1.1 million , calculated based on an imputed interest rate of 4.8% , that will be amortized over the term of the deposit to interest income along with a corresponding amount to cost of revenues. The deposit is due on demand in the first quarter of 2020 and was classified as other long-term assets on the Consolidated Balance Sheets. In January 2019, the Company paid an additional non-interest bearing deposit of $22.0 million to the contract manufacturer per the terms of the agreement. Interest income on the notes receivable is accrued and credited to interest income as it is earned, unless it is not probable the Company will collect the amounts due or if the present value of expected cash flows is less than the recorded investment. Interest income recognized was $8.4 million , $8.3 million , and $10.6 million , during the years ended December 31, 2018 , 2017 , and 2016 , respectively. 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 as of December 31, 2018 , 2017 , and 2016 . Warranties The Company accrues for warranty costs based on associated material, labor for customer support, and overhead at the time revenue is recognized. This accrual is reported within other accrued liabilities in the Consolidated Balance Sheets. Changes in the Company’s warranty reserve were as follows (in millions): As of December 31, 2018 2017 Beginning balance $ 27.4 $ 41.3 Provisions made during the period, net 30.7 36.7 Actual costs incurred during the period (30.1 ) (50.6 ) Ending balance $ 28.0 $ 27.4 Deferred Revenue Details of the Company's deferred revenue, as reported in the Consolidated Balance Sheets, were as follows (in millions): As of December 31, 2018 2017 Deferred product revenue: Undelivered product commitments and other product deferrals $ 163.3 $ 312.6 Distributor inventory and other sell-through items — 68.1 Deferred gross product revenue 163.3 380.7 Deferred cost of product revenue (18.9 ) (46.5 ) Deferred product revenue, net 144.4 334.2 Deferred service revenue 1,069.2 1,205.1 Total $ 1,213.6 $ 1,539.3 Reported as: Current $ 829.3 $ 1,030.3 Long-term 384.3 509.0 Total $ 1,213.6 $ 1,539.3 Deferred product revenue represents unrecognized revenue related to undelivered product commitments and other shipments that have not met revenue recognition criteria. Deferred service revenue represents billed amounts for service contracts, which include technical support, hardware and software maintenance, professional services, and training, for which services have not been rendered. At December 31, 2017, deferred product revenue also included unrecognized revenue related to shipments to distributors that had not sold through to end-users. Revenue See Note 13, Segments, for disaggregated revenue by product and service, customer vertical, and geographic region. Product revenue of $104.2 million included in deferred revenue at January 1, 2018 was recognized during the year ended December 31, 2018. Service revenue of $690.3 million included in deferred revenue at January 1, 2018 was recognized during the year ended December 31, 2018. The following table summarizes the transaction price for contracts that have not yet been recognized as revenue as of December 31, 2018 and when the Company expects to recognize the amounts as revenue (in millions): Revenue Recognition Expected by Period Total Less than 1 year 1-3 years More than 3 years Product $ 163.3 $ 131.2 $ 28.9 $ 3.2 Service 1,069.2 717.1 292.8 59.3 Total $ 1,232.5 $ 848.3 $ 321.7 $ 62.5 Deferred Commissions Deferred commissions were $33.7 million as of December 31, 2018 . During the year ended December 31, 2018, amortization expense for the deferred commissions was $144.2 million and there were no impairment charges recognized. Other Expense, Net Other expense, net consisted of the following (in millions): Years Ended December 31, 2018 2017 2016 Interest income $ 72.7 $ 53.0 $ 35.4 Interest expense (103.2 ) (101.2 ) (97.7 ) (Loss) gain on investments, net (7.4 ) 14.6 (1.8 ) Other (1.6 ) (2.7 ) 1.8 Other expense, net $ (39.5 ) $ (36.3 ) $ (62.3 ) Interest income primarily includes interest earned on the Company’s cash, cash equivalents, investments, and promissory note issued to the Company in connection with the sale of Junos Pulse. Interest expense primarily includes interest, net of capitalized interest expense, from long-term debt and customer financing arrangements. (Loss) gain on investments, net, primarily includes gains from the sale of investments in public and privately-held companies, and any observable changes in fair value and impairment charges recorded on these investments. Other typically consists of foreign exchange gains and losses and other non-operational income and expense items.

Restructuring Charges

Restructuring Charges	12 Months Ended
	Dec. 31, 2018
Restructuring and Related Activities [Abstract]
Restructuring Charges	Restructuring Charges The following table presents restructuring charges included in the Consolidated Statements of Operations (in millions): Years Ended December 31, 2018 2017 2016 Severance $ 8.3 $ 57.7 $ 2.8 Facilities — — 0.5 Contract terminations (1.0 ) 7.9 — Total $ 7.3 $ 65.6 $ 3.3 Reported as: Restructuring charges $ 7.3 $ 65.6 $ 3.3 Total $ 7.3 $ 65.6 $ 3.3 2018 Restructuring Plan During the third quarter of 2018, the Company initiated a restructuring plan (the "2018 Restructuring Plan") to realign its workforce as a result of organizational and leadership changes. In connection with the 2018 Restructuring Plan, the Company recorded $5.0 million of severance costs to restructuring charges in the Consolidated Statements of Operations during the year ended December 31, 2018 . The 2018 Restructuring Plan is substantially complete. Prior Restructuring Activities In 2017, the Company initiated a restructuring plan (the “2017 Restructuring Plan”) to realign its workforce and increase operational efficiencies. The 2017 Restructuring Plan consisted of severance and contract termination costs that were recorded to restructuring charges in the Consolidated Statement of Operations. During the year ended December 31, 2018 , in connection with the 2017 Restructuring Plan, the Company recorded $3.3 million of severance costs to restructuring charges and insignificant favorable adjustments for changes in previous estimates in the Consolidated Statements of Operations. The 2017 Restructuring Plan is substantially complete. In 2016, the Company recorded restructuring charges related to severance costs for certain former BTI employees as well as restructuring costs related to facilities. These activities were substantially completed as of December 31, 2017. Restructuring Liabilities Restructuring liabilities are reported within other accrued liabilities in the Consolidated Balance Sheets. The following table provides a summary of changes in the restructuring liabilities associated with the 2018 Restructuring Plan and prior year plans (in millions): December 31, Charges/ (Benefits) Cash December 31, Severance $ 17.7 $ 8.3 $ (25.0 ) $ 0.1 $ 1.1 Contract terminations and other 2.3 (1.0 ) (1.3 ) — — Total $ 20.0 $ 7.3 $ (26.3 ) $ 0.1 $ 1.1 The Company expects to substantially pay the remaining restructuring liabilities in the first quarter of 2019. See Note 18, Subsequent Events , for a discussion of the Company's restructuring plan initiated subsequent to December 31, 2018 .

Debt and Financing

Debt and Financing	12 Months Ended
	Dec. 31, 2018
Debt Instruments [Abstract]
Debt and Financing	Debt and Financing Debt The following table summarizes the Company's total debt (in millions, except percentages): As of December 31, 2018 Issuance date Maturity Date Amount Effective Interest Rates Senior Notes ("Notes"): 3.125% fixed-rate notes ("2019 Notes") February 2016 February 2019 $ 350.0 3.36 % 3.300% fixed-rate notes ("2020 Notes") March 2015 June 2020 300.0 3.47 % 4.600% fixed-rate notes March 2011 March 2021 300.0 4.69 % 4.500% fixed-rate notes (*) ("2024 Notes") March 2014 March 2024 350.0 4.63 % 4.500% fixed-rate notes (*) ("2024 Notes") February 2016 March 2024 150.0 4.87 % 4.350% fixed-rate notes ("2025 Notes") March 2015 June 2025 300.0 4.47 % 5.950% fixed-rate notes March 2011 March 2041 400.0 6.03 % Total Notes 2,150.0 Unaccreted discount and debt issuance costs (11.0 ) Total $ 2,139.0 ________________________________ (*) 2024 Notes issued in March 2014 and February 2016 form a single series and are fully fungible. 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. As of December 31, 2018 , the Company's aggregate debt maturities based on outstanding principal were as follows (in millions): Years Ending December 31, Amount 2019 $ 350.0 2020 300.0 2021 300.0 2022 — 2023 — Thereafter 1,200.0 Total $ 2,150.0 The Company may redeem the 2020 Notes and 2025 Notes, either in whole or in part, at any time one month prior to the maturity date of the 2020 Notes, and three months prior to the maturity date of the 2025 Notes, at a redemption price equal to the greater of (i) 100% of the aggregate principal amount of the 2020 Notes and 2025 Notes to be redeemed or (ii) the sum of the present values of the remaining scheduled payments discounted at the Treasury rate plus 30 basis points for the 2020 Notes, or the Treasury rate plus 37.5 basis points for the 2025 Notes, plus, in the case of each of the clauses (i) and (ii) above, accrued and unpaid interest, if any. At any time on or after May 15, 2020, in the case of the 2020 Notes, and at any time on or after March 15, 2025, in the case of the 2025 Notes, the Company may redeem Notes of such series, in whole or in part, at a redemption price equal to 100% of the principal amount of the 2020 Notes and the 2025 Notes to be redeemed, plus accrued and unpaid interest, if any. The Company may redeem the other Notes, either in whole or in part, at any time at a redemption price equal to the greater of (i) 100% of the aggregate principal amount of the Notes to be redeemed or (ii) the sum of the present values of the remaining scheduled payments discounted to the redemption date, plus, in either case, accrued and unpaid interest, if any. 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. Interest on the Notes is payable in cash semiannually. The effective interest rates for the Notes include the interest on the Notes, accretion of the discount, and amortization of issuance costs. 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 December 31, 2018 , 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 and Citibank, N.A., as administrative agent, that provides for a $500.0 million unsecured revolving credit facility, with an option of the Company to increase the amount of the credit facility by up to an additional $200.0 million , subject to the lenders' approval. Proceeds of loans made under the Credit Agreement may be used by the Company for working capital and general corporate purposes. Revolving loans may be borrowed, repaid and reborrowed until June 27, 2019, at which time all amounts borrowed must be repaid. Borrowing may be denominated, at the Company's option in U.S. dollars, Pounds Sterling or Euro. 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. Base rate is defined as the greatest of (A) Citibank's base rate , (B) the Federal Funds rate plus 0.50% or (C) the ICE Benchmark Administration Settlement Rate applicable to dollars for a period of one month plus 1.00% . The Eurocurrency rate is determined for U.S. dollars and Pounds Sterling as the rate at which deposits in such currency are offered in the London interbank market for the applicable interest period and for Euro as the rate specified for deposits in Euro with a maturity comparable to the applicable interest period. As of December 31, 2018 , the Company has not borrowed any funds under the Credit Agreement and was in compliance with all covenants in the Credit Agreement. 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 receivables of $122.8 million , $169.4 million and $95.6 million during the years ended December 31, 2018 , 2017 , and 2016 , respectively. The Company received cash proceeds from financing providers of $123.2 million , $169.3 million , and $83.2 million during the years ended December 31, 2018 , 2017 , and 2016 , respectively. As of December 31, 2018 and December 31, 2017 , the amounts owed by the financing providers were $17.2 million and $13.7 million , respectively, which were recorded in accounts receivable on the Company’s Consolidated Balance Sheets. The portion of the receivable financed that has not been recognized as revenue is accounted for as a financing arrangement and is included in other accrued liabilities in the Consolidated Balance Sheets. There was no outstanding balance as of December 31, 2018 . Cash received from the financing provider not recognized as revenue was $16.9 million as of December 31, 2017 .

Equity

Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Equity	Equity The following table summarizes dividends paid, stock repurchases and retirements under the Company's stock repurchase programs, and stock repurchases for tax withholdings (in millions, except per share amounts): Dividends Stock Repurchases Total Year Per Share Amount Shares Average price Amount Tax Withholding Amount Amount 2018 (1) $ 0.72 $ 249.3 29.3 $ 25.62 $ 750.0 $ 6.6 $ 1,005.9 2017 (2) $ 0.40 $ 150.4 26.1 $ 27.61 $ 719.7 $ 6.1 $ 876.2 2016 (2) $ 0.40 $ 152.5 13.5 $ 23.25 $ 312.9 $ 11.7 $ 477.1 ________________________________ (1) Shares repurchased under the 2018 Stock Repurchase Program. $750.0 million represents the full amount of the ASR for which 23.3 million shares were received initially during the first quarter of 2018, and an additional 6.0 million shares were received at final settlement during the third quarter of 2018. (2) Shares repurchased under the 2014 Stock Repurchase Program. Cash Dividends on Shares of Common Stock During 2018 , the Company declared four quarterly cash dividends of $0.18 per share on its common stock on January 30, 2018, May 2, 2018, July 26, 2018 and October 24, 2018, which were paid on March 22, 2018, June 22, 2018, September 25, 2018 and December 26, 2018, respectively, to stockholders of record as of the close of business on March 1, 2018, June 1, 2018, September 4, 2018, and December 5, 2018, respectively. Any future dividends, and the establishment of record and payment dates, are subject to approval by the Board of Directors (the "Board") of Juniper Networks or an authorized committee thereof. See Note 18, Subsequent Events, for discussion of the Company's dividend declaration subsequent to December 31, 2018 . Stock Repurchase Activities In January 2018, the Board approved a $2.0 billion share repurchase program ("2018 Stock Repurchase Program"), including $750.0 million to be used pursuant to an accelerated share repurchase program. The 2018 Stock Repurchase Program replaces the previous authorization approved by the Board in 2014 ("2014 Stock Repurchase Program"). As part of the 2018 Stock Repurchase Program, in February 2018, the Company entered into an accelerated share repurchase program (the "ASR") with two financial institutions to repurchase $750.0 million of the Company's common stock. During the first quarter of 2018, the Company made an up-front payment of $750.0 million pursuant to the ASR and received an initial 23.3 million shares of the Company's common stock, based on the market value of the Company's common stock on the date of the transaction. During the third quarter of 2018, the ASR was completed and an additional 6.0 million shares were received from the financial institutions for a total repurchase of 29.3 million shares of the Company's common stock at a volume weighted average repurchase price, less an agreed upon discount, of $25.62 per share. The shares received with respect to the ASR were retired and accounted for as a reduction to stockholders' equity in the Consolidated Balance Sheets. As of December 31, 2018 , there were $1.3 billion of authorized funds remaining under the 2018 Stock Repurchase Program. Future share repurchases under the 2018 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 Company's 2018 Stock Repurchase Program may be discontinued at any time. Accumulated Other Comprehensive Loss, Net of Tax The components of accumulated other comprehensive loss, net of related taxes, for the years ended December 31, 2018 , 2017 , and 2016 were as follows (in millions): Unrealized Gains/Losses on Available-for- Sale Debt Securities (1) Unrealized Gains/Losses on Cash Flow Hedges (2) Foreign Currency Translation Adjustments Total Balance as of December 31, 2015 $ 17.0 $ (1.3 ) $ (34.9 ) $ (19.2 ) Other comprehensive income (loss) before reclassifications 0.8 (2.1 ) (14.5 ) (15.8 ) Amount reclassified from accumulated other comprehensive loss (1.2 ) (1.1 ) — (2.3 ) Other comprehensive loss, net (0.4 ) (3.2 ) (14.5 ) (18.1 ) Balance as of December 31, 2016 $ 16.6 $ (4.5 ) $ (49.4 ) $ (37.3 ) Other comprehensive income before reclassifications 4.5 15.7 19.0 39.2 Amount reclassified from accumulated other comprehensive loss (2.1 ) (5.2 ) — (7.3 ) Other comprehensive income, net 2.4 10.5 19.0 31.9 Balance as of December 31, 2017 $ 19.0 $ 6.0 $ (30.4 ) $ (5.4 ) Other comprehensive income (loss) before reclassifications 0.6 (6.4 ) (12.4 ) (18.2 ) Amount reclassified from accumulated other comprehensive income (loss) 0.9 (1.2 ) — (0.3 ) Other comprehensive income (loss), net 1.5 (7.6 ) (12.4 ) (18.5 ) Reclassification of tax effects upon adoption of ASU 2018-02 5.0 0.7 — 5.7 Balance as of December 31, 2018 $ 25.5 $ (0.9 ) $ (42.8 ) $ (18.2 ) ________________________________ (1) The reclassifications out of accumulated other comprehensive loss during the years ended December 31, 2018 , 2017 , and 2016 for realized gains on available-for-sale debt securities were not material, and were included in other expense, net, in the Consolidated Statements of Operations. (2) The reclassifications out of accumulated other comprehensive loss during the years ended December 31, 2018 , 2017 , and 2016 for realized gains and losses 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 Consolidated Statements of Operations.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Employee Benefit Plans	Employee Benefit Plans Equity Incentive Plans The Company’s equity incentive plans include the 2015 Equity Incentive Plan (the “2015 Plan”), the 2006 Equity Incentive Plan (the “2006 Plan”), and the 2008 Employee Stock Purchase Plan (the “ESPP”). Under these plans, the Company has granted stock options, RSUs, and PSAs. In addition, in connection with certain past acquisitions, the Company has assumed or substituted stock options, RSUs, RSAs, and PSAs granted under the stock plans of the acquired companies. Such awards were converted into or replaced with the Company's stock options, RSUs, RSAs, and PSAs, respectively. The 2015 Plan was adopted and approved by the Company's stockholders in May 2015 and had an initial authorized share reserve of 38.0 million shares of common stock, plus the addition of any shares subject to outstanding awards under the 2006 Plan and the Amended and Restated 1996 Stock Plan that were outstanding as of May 19, 2015, and that subsequently expire or otherwise terminate, up to a maximum of an additional 29.0 million shares. In May 2017, the Company's stockholders approved an additional 23.0 million shares of common stock for issuance under the 2015 Plan. As of December 31, 2018 , an aggregate of 15.3 million shares were subject to outstanding equity awards under the 2015 Plan and the 2006 Plan. As of December 31, 2018 , 21.9 million shares were available for future issuance under the 2015 Plan and no shares were available for future issuance under the 2006 Plan or the 1996 Plan. The ESPP was adopted and approved by the Company's stockholders in May 2008. To date, the Company's stockholders have approved a share reserve of 35.0 million shares of the Company's common stock for issuance under the ESPP. The ESPP permits eligible employees to acquire shares of the Company’s common stock at a 15% discount (as determined in the ESPP) through periodic payroll deductions of up to 10% of base compensation, subject to individual purchase limits of 6,000 shares in any twelve -month period or $25,000 worth of stock, determined at the fair market value of the shares at the time the stock purchase option is granted, in one calendar year. On November 6, 2017, the Company’s Compensation Committee amended and restated the ESPP to provide that for the offering period that began on February 1, 2018 would be for 24 months with four 6 -month purchase periods. A new 24-month offering period will commence every six months thereafter. The purchase price for the Company’s common stock under the ESPP is 85% of the lower of the fair market value of the shares at (1) the beginning of the applicable offering period or (2) the end of each 6 -month purchase period during such offering period. The ESPP will continue in effect until February 25, 2028, unless terminated earlier under the provisions of the ESPP. As of December 31, 2018 , approximately 26.3 million shares have been issued and 8.7 million shares remain available for future issuance under the ESPP. During 2018, 2017, and 2016, the Company completed the acquisitions of HTBase, Cyphort, AppFormix, Aurrion, and BTI. In connection with these acquisitions, the Company assumed or substituted an aggregate of 4.1 million shares of stock options, RSUs, RSAs, and PSAs. No additional awards can be granted under the stock plans of the acquired companies. As of December 31, 2018 , approximately 2.2 million shares of common stock were outstanding under all awards assumed or substituted through the Company's acquisitions. RSU, RSA, and PSA Activities RSUs and RSAs generally vest over three years from the date of grant, and PSAs generally vest over a period of two to three years provided that certain annual performance targets and other vesting criteria are met. Until vested, RSUs and PSAs do not have the voting and dividend participation rights of common stock and the shares underlying the awards are not considered issued and outstanding. The following table summarizes the Company’s RSU, RSA, and PSA activity and related information as of and for the year ended December 31, 2018 (in millions, except per share amounts and years): Outstanding RSUs, RSAs, and PSAs (6) Number of Shares Weighted Average Grant-Date Fair Value per Share Weighted Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance at December 31, 2017 19.5 $ 25.39 RSUs granted (1)(2) 7.4 25.40 RSUs substituted in acquisitions (2)(5) 0.1 26.26 RSAs substituted in acquisitions (2)(5) 0.1 27.66 PSAs granted (2)(4) 0.9 24.62 RSUs vested (3) (6.5 ) 25.67 RSAs vested (3) (0.2 ) 25.12 PSAs vested (3) (1.1 ) 24.14 RSUs canceled (2.0 ) 25.92 PSAs canceled (0.8 ) 24.45 Balance at December 31, 2018 17.4 $ 25.32 1.0 $ 467.6 As of December 31, 2018 Vested and expected-to-vest RSUs, RSAs, and PSAs 15.5 $ 25.31 1.0 $ 418.4 ________________________________ (1) Includes service-based and market-based RSUs granted under the 2015 Plan according to their terms. (2) The weighted-average grant-date fair value of RSUs, RSAs, and PSAs granted and assumed or substituted during 2018 , 2017 , and 2016 was $25.33 , $27.53 , and $24.66 , respectively. (3) Total fair value of RSUs, RSAs, and PSAs vested during 2018 , 2017 , and 2016 was $200.5 million , $187.3 million , and $185.7 million , respectively. (4) 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 are achieved at target is 0.7 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 million to 1.0 million shares. (5) RSUs and RSAs substituted in connection with the acquisition of HTBase. (6) Excludes 1.9 million shares of PSAs that were modified in 2018, which relate primarily to PSAs assumed by the Company in connection with acquisitions consummated in 2016. These awards are contingent upon the achievement of certain performance milestones. The total incremental compensation cost resulting from the modifications totaled $6.9 million to be recognized over the remaining terms of the modified awards. Shares Available for Grant The following table presents the stock activity and the total number of shares available for grant under the 2015 Plan (in millions): Number of Shares Balance as of December 31, 2017 33.5 Additional shares authorized — RSUs and PSAs granted (1) (17.7 ) RSUs and PSAs canceled (2) 5.4 Options canceled/expired (2) 0.7 Balance as of December 31, 2018 21.9 ________________________________ (1) RSUs and PSAs with a per share or unit purchase price lower than 100% of the fair market value of the Company's common stock on the day of the grant under the 2015 Plan are counted against shares authorized under the plan as two and one-tenth shares of common stock for each share subject to such award. The number of shares subject to PSAs granted represents the maximum number of shares that may be issued pursuant to the award over its full term. (2) Canceled or expired options and canceled RSUs and PSAs under the 2006 Plan are no longer available for future grant under such plan; however, the number of shares available for grant under the 2015 Plan are increased by (i) the amount of such canceled or expired options and (ii) two and one-tenth the shares for each canceled RSUs or PSAs, as applicable, up to a maximum of 29.0 million additional shares of common stock, pursuant to the terms of the 2015 Plan. Employee Stock Purchase Plan The Company's ESPP is implemented in a series of offering periods, each six months in duration, or a shorter period as determined by the Board. Employees purchased 2.5 million shares of common stock through the ESPP during 2018 , and 2.7 million shares in both 2017 and 2016 at an average exercise price of $22.31 , $20.83 , and $19.66 per share, respectively. Valuation Assumptions The weighted-average assumptions used and the resulting estimates of fair value for ESPP and market-based RSUs were as follows: Years Ended December 31, 2018 2017 2016 ESPP: Volatility 29% 25% 32% Risk-free interest rate 1.9% 0.9% 0.4% Expected life (years) 1.2 0.5 0.5 Dividend yield 2.7% 1.5% 1.8% Weighted-average fair value per share $6.93 $6.04 $5.56 Market-based RSUs: Volatility 28% 30% 36% Risk-free interest rate 2.4% 1.9% 1.2% Dividend yield 2.6% 1.4% 1.7% Weighted-average fair value per share $28.39 $19.30 $14.71 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 Company's Consolidated Statements of Operations (in millions): Years Ended December 31, 2018 2017 2016 Cost of revenues - Product $ 6.3 $ 4.6 $ 6.4 Cost of revenues - Service 18.0 17.5 15.3 Research and development 120.6 86.6 126.5 Sales and marketing 51.1 55.6 55.2 General and administrative 21.1 23.2 23.4 Total $ 217.1 $ 187.5 $ 226.8 The following table summarizes share-based compensation expense by award type (in millions): Years Ended December 31, 2018 2017 2016 Stock options $ 0.4 $ 0.5 $ 4.4 RSUs, RSAs, and PSAs 198.2 171.3 206.9 ESPP 18.5 15.7 15.5 Total $ 217.1 $ 187.5 $ 226.8 For the years ended December 31, 2018 , 2017 and 2016 , the Company recognized tax benefits on total stock-based compensation expense, which are reflected in the income tax provision in the Consolidated Statements of Operations, of $33.8 million , $29.1 million , and $53.3 million , respectively. For the years ended December 31, 2018 , 2017 and 2016 , the realized tax benefit related to awards vested or exercised during the period was $38.9 million , $64.1 million and $58.6 million , respectively. These amounts do not include the indirect effects of stock-based awards, which primarily relate to the research and development tax credit. As of December 31, 2018 , the total unrecognized compensation cost related to unvested share-based awards was $280.4 million to be recognized over a weighted-average period of 1.4 years. 401(k) Plan The Company maintains a savings and retirement plan qualified under Section 401(k) of the Internal Revenue Code of 1986, as amended (the "IRC"). Employees meeting the eligibility requirements, as defined under the IRC, may contribute up to the statutory limits each year. The Company currently matches 30% of all eligible employee contributions which vest immediately. The Company’s matching contributions to the plan totaled $20.2 million , $21.1 million , and $20.7 million during 2018 , 2017 , and 2016 , respectively. Deferred Compensation Plan The Company’s NQDC plan is an unfunded and unsecured deferred compensation arrangement. Under the NQDC plan, officers and other senior employees may elect to defer a portion of their compensation and contribute such amounts to one or more investment funds. As of December 31, 2018 , the liability of the Company to the plan participants was $24.3 million , of which $3.6 million was included within other accrued liabilities and $20.7 million was included in other long-term liabilities on the Consolidated Balance Sheets. The Company had investments of $24.3 million correlating to the deferred compensation obligations, of which $3.6 million was included within prepaid expenses and other current assets and $20.7 million was included within other long-term assets on the Consolidated Balance Sheets. As of December 31, 2017 , the liability of the Company was $27.6 million , of which $4.9 million was included within other accrued liabilities and $22.7 million was included in other long-term liabilities on the Consolidated Balance Sheets. The Company had investments of $27.6 million correlating to the deferred compensation obligations, of which $4.9 million was included within prepaid expenses and other current assets and $22.7 million was included within other long-term assets on the Consolidated Balance Sheets. Non-US Pension Plans The Company maintains the India Gratuity Trust and Israel Retirement Trust (or "the Pension Plans") to cover statutory severance obligations in the event of termination of any of its India and Israel employees, respectively. The Pension Plans are primarily invested in mutual funds and measured at fair value using Level 1 hierarchy on a recurring basis. The Company reports the Pension Plans on a net basis on the Consolidated Balance Sheets. As of December 31, 2018 and December 31, 2017 , the fair value of the Pension Plans was $13.1 million and $11.3 million , respectively. As of December 31, 2018 and December 31, 2017 , the Company recorded a net plan liability of $2.5 million and $4.3 million , respectively, in accrued compensation on the Consolidated Balance Sheets.

Segments

Segments	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segments	Segments The Company operates in one reportable segment. The Company's chief executive officer, who is the 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): Years Ended December 31, 2018 2017 2016 Routing $ 1,839.7 $ 2,189.5 $ 2,352.9 Switching 934.4 963.4 858.0 Security 333.0 293.3 318.0 Total product 3,107.1 3,446.2 3,528.9 Total service 1,540.4 1,581.0 1,461.2 Total $ 4,647.5 $ 5,027.2 $ 4,990.1 The following table presents net revenues by customer vertical (*) (in millions): Years Ended December 31, 2018 2017 2016 Cloud $ 1,049.9 $ 1,310.7 $ 1,315.9 Service Provider 2,066.7 2,319.4 2,316.4 Enterprise 1,530.9 1,397.1 1,357.8 Total $ 4,647.5 $ 5,027.2 $ 4,990.1 ________________________________ (*) Certain prior-period amounts have been reclassified to conform to the current-period classifications. 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): Years Ended December 31, 2018 2017 2016 Americas: United States $ 2,339.1 $ 2,712.6 $ 2,737.0 Other 202.1 234.6 231.8 Total Americas 2,541.2 2,947.2 2,968.8 Europe, Middle East, and Africa 1,290.8 1,195.8 1,238.1 Asia Pacific 815.5 884.2 783.2 Total $ 4,647.5 $ 5,027.2 $ 4,990.1 During the years ended December 31, 2018 , 2017 , and 2016 , no customer accounted for greater than 10% of the Company's net revenues. The following table presents geographic information for property and equipment, net and purchased intangible assets, net (in millions): As of December 31, 2018 2017 United States $ 941.7 $ 1,005.1 International 128.5 144.1 Property and equipment, net and purchased intangible assets, net $ 1,070.2 $ 1,149.2 The Company tracks assets by physical location. The majority of the Company’s assets, excluding cash and cash equivalents and investments, as of December 31, 2018 and December 31, 2017 , were attributable to U.S. operations.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of pretax income are summarized as follows (in millions): Years Ended December 31, 2018 2017 2016 Domestic $ 160.6 $ 474.2 $ 466.2 Foreign 372.1 337.6 361.2 Total pretax income $ 532.7 $ 811.8 $ 827.4 The (benefit) provision for income taxes is summarized as follows (in millions): Years Ended December 31, 2018 2017 2016 Current (benefit) provision: Federal $ (126.1 ) $ 594.3 $ 121.4 States 9.0 13.9 10.3 Foreign 38.9 45.4 46.0 Total current (benefit) provision (78.2 ) 653.6 177.7 Deferred (benefit) provision: Federal 36.6 (128.7 ) 57.2 States 2.2 (17.7 ) 4.3 Foreign 5.2 (1.6 ) (4.5 ) Total deferred (benefit) provision 44.0 (148.0 ) 57.0 Total (benefit) provision for income taxes $ (34.2 ) $ 505.6 $ 234.7 The (benefit) provision for income taxes differs from the amount computed by applying the federal statutory rate of 21% for 2018 and 35% for 2017 and 2016, respectively, to pretax income as follows (in millions): Years Ended December 31, 2018 2017 2016 Expected provision at statutory rate $ 111.9 $ 284.1 $ 289.6 State taxes, net of federal benefit 7.4 12.0 8.9 Foreign income at different tax rates (12.8 ) (46.4 ) (53.4 ) R&D tax credits (22.1 ) (15.1 ) (16.8 ) Share-based compensation 4.7 — 10.5 Release of valuation allowance — (1.7 ) (0.7 ) Domestic production activities — (12.4 ) (9.5 ) Non-deductible compensation 1.9 1.6 2.4 Impact of the U.S. Tax Cuts and Jobs Act 2.8 289.5 — Tax accounting method changes (65.4 ) — — Lapses in federal statutes of limitations (67.6 ) — — Other 5.0 (6.0 ) 3.7 Total (benefit) provision for income taxes $ (34.2 ) $ 505.6 $ 234.7 In 2018, the Company recorded a $67.6 million benefit related to a lapse in the federal statute of limitations relative to tax years 2010 through 2014, including interest, a $33.2 million benefit as a result of filing a change in accounting method for the tax recognition of deferred product revenue in the U.S. to better align with the financial statement recognition of such revenue, and a $32.2 million benefit resulting from tax accounting method change related to foreign deferred service revenue. The Tax Act introduced significant changes to U.S. income tax law. Effective January 1, 2018, the Tax Act reduced the U.S. federal corporate income tax rate from 35% to 21%, created a minimum tax on foreign earnings and imposed a one-time transition tax on accumulated foreign earnings through December 31, 2017. In 2017, the Company recorded provisional amounts for the effects of the Tax Act of $289.5 million primarily related to net taxes on accumulated foreign earnings and the re-measurement of the Company’s deferred tax assets at the revised U.S. statutory rate. In the fourth quarter of 2018, the Company completed its analysis to determine the effect of the Tax Act and recorded immaterial adjustments as of December 31, 2018. The Company accounts for U.S. tax on certain foreign subsidiaries income, which is referred to as Global Intangible Low-Taxed Income (“GILTI”) in the year earned. Therefore, the Company has not provided any deferred tax impacts of GILTI in its Consolidated Financial Statements for the year ended December 31, 2018. Deferred income taxes reflect the net tax effects of tax carry-forward items and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company's long-term deferred tax assets and deferred tax liabilities are as follows (in millions): As of December 31, 2018 2017 Deferred tax assets: Net operating loss carry-forwards $ 12.9 $ 18.3 Research and other credit carry-forwards 220.0 198.8 Deferred revenue 37.7 103.5 Share-based compensation 26.1 31.1 Cost sharing adjustment 12.2 12.4 Reserves and accruals not currently deductible 62.7 76.7 Other 13.2 12.8 Total deferred tax assets 384.8 453.6 Valuation allowance (233.7 ) (214.5 ) Deferred tax assets, net of valuation allowance 151.1 239.1 Deferred tax liabilities: Property and equipment basis differences (40.6 ) (42.5 ) Purchased intangibles (13.7 ) (12.4 ) Unremitted foreign earnings (26.4 ) (25.4 ) Deferred compensation and other (8.9 ) (10.4 ) Total deferred tax liabilities (89.6 ) (90.7 ) Net deferred tax assets $ 61.5 $ 148.4 Based on changes provided by the Tax Act, the Company re-measured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. As of December 31, 2018 and 2017 , the Company had a valuation allowance on its U.S. domestic deferred tax assets of approximately $233.7 million and $214.5 million , respectively. The balance at December 31, 2018 consisted of approximately $206.0 million , $20.2 million and $3.1 million against the Company's California, Massachusetts and Canadian deferred tax assets, respectively, which the Company believes are not more likely than not to be utilized in future years. The remaining deferred tax assets on which the Company recorded valuation allowance of approximately $4.4 million related to losses that are capital in nature and may carry forward to offset future capital gains only. The valuation allowance increased in 2018 and 2017 by $19.2 million and $60.1 million , respectively, primarily related to the change in California, Massachusetts and Canadian R&D tax credits. As of December 31, 2018 , the Company had federal and California net operating loss carry-forwards of approximately $54.4 million and $150.4 million , respectively. The California net operating loss carry-forwards of $150.4 million are expected to expire unused. The Company also had federal and California tax credit carry-forwards of approximately $2.6 million and $244.1 million , respectively. Unused net operating loss carry-forwards will expire at various dates beginning in the year 2019. The California tax credit carry-forwards will carry forward indefinitely. As of December 31, 2018 , 2017 , and 2016 , the total amount of gross unrecognized tax benefits was $178.1 million , $264.5 million , and $223.1 million , respectively. As of December 31, 2018 , approximately $175.3 million of the $178.1 million gross unrecognized tax benefits, if recognized, would affect the effective tax rate. A reconciliation of the beginning and ending amount of the Company's total gross unrecognized tax benefits was as follows (in millions): Years Ended December 31, 2018 2017 2016 Balance at beginning of year $ 264.5 $ 223.1 $ 216.1 Tax positions related to current year: Additions 4.3 64.6 27.2 Tax positions related to prior years: Additions 12.7 1.8 1.0 Reductions (33.8 ) (16.6 ) (4.1 ) Settlements (2.6 ) (4.0 ) (14.3 ) Lapses in statutes of limitations (67.0 ) (4.4 ) (2.8 ) Balance at end of year $ 178.1 $ 264.5 $ 223.1 As of December 31, 2018 , 2017 , and 2016 , the Company had accrued interest and penalties related to unrecognized tax benefits of $33.8 million , $40.7 million , and $31.3 million , respectively, to other long-term liabilities in the Consolidated Balance Sheets. Due to the changes in the level of gross unrecognized tax benefit, the Company recognized a benefit for net interest and penalties of $5.2 million and an expense of $8.5 million and $6.0 million in its Consolidated Statements of Operations during the years ended December 31, 2018 , 2017 , and 2016 , respectively. On November 30, 2018, the Company received a final order from the India Supreme Court, which resolved the Company’s dispute with the India Tax Authorities for the 2004 through 2008 income tax years. The final order from the Court effectively concludes the tax investigation for the respective tax years, and as a result the Company released $5.4 million of previously unrecognized tax benefits, including $4.6 million of interest and penalties. In 2018, the U.K., German and Australian tax authorities concluded examinations of the 2016 tax year, 2010 through 2013 tax years and the 2016 through 2017 tax years, respectively, which did not have a material impact to the Company’s financial statements. The Company engages in continuous discussions and negotiations with tax authorities regarding tax matters in various jurisdictions. There is a greater than remote likelihood that the balance of the gross unrecognized tax benefits will decrease by approximately $7.7 million within the next twelve months due to lapses of applicable statutes of limitation and the completion of tax review cycles in various tax jurisdictions. The Company conducts business globally and, as a result, Juniper Networks or one or more of its subsidiaries files income tax returns in the U.S. federal jurisdiction and various state and foreign jurisdictions. In the normal course of business, the Company is subject to examination by taxing authorities throughout the world, including such major jurisdictions as the Netherlands, U.K., France, Germany, Japan, China, Australia, India, and the U.S. With few exceptions, the Company is no longer subject to U.S. federal, state and local, and non-U.S. income tax examinations for years before 2007. The Company is currently under examination by the IRS for the 2007 through 2009 tax years and by the India tax authorities for the 2009 through 2015 tax years. In March 2016, the IRS concluded its field audit and issued a final assessment. The Company is appealing this assessment. The examinations by the India tax authorities are ongoing. The Company regularly assesses the likelihood of an adverse outcome resulting from such examinations. As of December 31, 2018 , the Company believes the resolution of the audits is unlikely to have a material effect on its consolidated financial condition or results of operations. The Company is pursuing all available administrative remedies relative to these ongoing matters. The Company believes that it has adequately provided for any reasonably foreseeable outcomes related to these proposed adjustments and the ultimate resolution of these matters is unlikely to have a material effect on its consolidated financial condition or results of operations; however, there is still a possibility that an adverse outcome of these matters could have a material effect on its consolidated financial condition and results of operations.

Net Income Per Share

Net Income Per Share	12 Months Ended
	Dec. 31, 2018
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): Years Ended December 31, 2018 2017 2016 Numerator: Net income $ 566.9 $ 306.2 $ 592.7 Denominator: Weighted-average shares used to compute basic net income per share 349.0 377.7 381.7 Dilutive effect of employee stock awards 5.4 6.5 6.1 Weighted-average shares used to compute diluted net income per share 354.4 384.2 387.8 Net income per share: Basic $ 1.62 $ 0.81 $ 1.55 Diluted $ 1.60 $ 0.80 $ 1.53 Anti-dilutive shares 3.9 1.1 2.5 Basic net income per share is computed using net income available to common stockholders and the weighted-average number of common shares outstanding for the period. Diluted net income per share is computed using net income available to common stockholders and the weighted-average number of common shares outstanding plus potentially dilutive common shares outstanding during the period. Dilutive potential common shares consist of common shares issuable upon exercise of stock options, issuances of ESPP, and vesting of RSUs, RSAs, and PSAs. The Company includes the common shares underlying PSAs in the calculation of diluted net income per share only when they become contingently issuable. Anti-dilutive shares are excluded from the computation of diluted net income per share.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments The following table summarizes the Company’s unconditional purchase obligations and future minimum payments under non-cancelable operating and other lease arrangements for each of the next five years and thereafter as of December 31, 2018 (in millions): Leases Years Ending December 31, Unconditional Purchase Obligations Operating Leases Other Lease Arrangement 2019 $ 43.1 $ 33.7 $ 13.1 2020 26.4 30.7 13.3 2021 11.4 24.3 13.6 2022 8.5 17.0 13.9 2023 5.5 14.3 14.2 Thereafter 2.9 26.3 32.9 Total $ 97.8 $ 146.3 $ 101.0 In December 2018, the Company entered into a Master Services Agreement and certain Statements of Work, (collectively, the “Agreement”) with International Business Machines Corporation ("IBM") pursuant to which the Company will outsource significant portions of its IT and other administrative functions following a transition period. Under the Agreement, IBM will provide the Company a broad range of IT services such as applications, including support, development and maintenance; infrastructure management and support, including for servers, storage and network devices; and end user support including service desk. The Agreement has an initial term through 2026 over which period the Company will pay IBM a combination of fixed and variable fees, fluctuating based on the Company's actual need for the services utilized. The Company expects to pay IBM approximately $325.0 million . The table above does not include fees payable to IBM under the contract as the Company is unable to make a reasonably reliable estimate of the amount of the payments related to this contract due to uncertainties in the usage of the services. Unconditional Purchase Obligations Unconditional purchase obligations consist of agreements that include firm and non-cancelable terms to transfer funds in the future for fixed or minimum amounts or quantities to be purchased at fixed or minimum prices. These obligations primarily result from contracts entered into for the acquisition of software development services and product development. For obligations with cancellation provisions, the amounts included in the preceding table were limited to the non-cancelable portion of the agreement terms or the minimum cancellation fee. In May 2018, the Company entered into a strategic alliance with Ericsson AB ("Ericsson") under which both companies have agreed to undertake certain development, testing and related work to bring specific products to market. The alliance has an initial term through 2023. As of December 31, 2018, the minimum fixed fees payable to Ericsson was $18.0 million . Operating Leases The Company leases its facilities and certain equipment under non-cancelable operating leases that expire at various dates through November 2029 . Certain leases require the Company to pay variable costs such as taxes, maintenance, and insurance and include renewal options and escalation clauses. Rent expense for 2018 , 2017 , and 2016 was approximately $39.0 million , $39.3 million , and $37.9 million , respectively. Other Lease Arrangement In July 2015, the Company entered into a lease arrangement through March 2026 for approximately 63,000 square feet of space in the State of Washington. The space is used, among other things, to consolidate certain of the Company's laboratory operations currently located in Sunnyvale, California. Due to certain contractual obligations during the construction period, the Company was deemed the owner of the property during that period. The Company capitalized the construction costs by recording a build-to-suit lease asset and a corresponding build-to-suit financing liability. Upon the completion of construction in 2016, the Company concluded that it had a certain form of continuing economic involvement in the facility, which precluded sale-leaseback accounting treatment. As a result, a total of $60.9 million of costs capitalized were placed in service and are being depreciated over the lease term. As of December 31, 2018 , the total payment under the lease agreement over the ten -year term is approximately $101.0 million of which $59.7 million is included in other-long term liabilities on the Consolidated Balance Sheets. Purchase Commitments with Contract Manufacturers and Suppliers In order to reduce manufacturing lead times and in the interest of having access to adequate component supply, the Company enters into agreements with contract manufacturers and certain suppliers to procure inventory based on the Company's requirements. A significant portion of the Company's purchase commitments arising from these agreements consists of firm and non-cancelable commitments. These purchase commitments totaled $663.3 million as of December 31, 2018 . The Company establishes a liability in connection with purchase commitments related to quantities in excess of its demand forecasts or obsolete materials charges for components purchased by the contract manufacturers based on the Company’s demand forecast or customer orders. As of December 31, 2018 , the Company had accrued $30.4 million based on its estimate of such charges. Debt and Interest Payment on Debt As of December 31, 2018 , the Company held total outstanding debt consisting of the Notes with a carrying value of $2,139.0 million . See Note 10, Debt and Financing , for further discussion of the Company's long-term debt and expected future principal maturities. Tax Liability In the fourth quarter of 2018, the Company completed its analysis to determine the effect of the Tax Act and recorded immaterial adjustments as of December 31, 2018. The Company has elected to pay its transition tax, net of applicable tax refunds, over the eight-year period provided in the Tax Act. The long-term income taxes payable of $245.2 million represents the remaining balance of the Company's transition tax obligation. As of December 31, 2018 , the Company had $159.2 million included in long-term income taxes payable on the Consolidated Balance Sheets for unrecognized tax positions. At this time, the Company is unable to make a reasonably reliable estimate of the timing of payments related to this amount due to uncertainties in the timing of tax audit outcomes. 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 December 31, 2018 and 2017 , the Company recorded $11.9 million and $20.4 million , respectively, for such indemnification obligations in other accrued liabilities and other long-term liabilities on the Consolidated Balance Sheets. The Company also has financial guarantees consisting of guarantees of product and service performance and standby letters of credit for certain lease facilities and insurance programs of $23.1 million and $23.0 million , as of December 31, 2018 and December 31, 2017 , respectively. Legal Proceedings Investigations The Company previously disclosed that it has been the subject of investigations by the U.S. Securities and Exchange Commission ("SEC") and the U.S. Department of Justice ("DOJ") into possible violations by the Company of the U.S. Foreign Corrupt Practices Act ("FCPA"). In cooperation with these investigations, the Company and the Audit Committee of the Board of Directors, with the assistance of outside counsel and other independent advisors, conducted a thorough internal investigation. As a result of its internal investigation, the Company made significant improvements in its internal controls and carried out a number of disciplinary actions. In the fourth quarter of 2017, the DOJ notified the Company that the DOJ has closed its investigation related to these matters without taking any action against the Company. The Company is continuing to fully cooperate with the SEC’s ongoing investigation, and based on the Company’s recent communications with the Staff of the SEC, the Company believes that it is likely that the Staff of the SEC will seek to bring an enforcement action against the Company. The Company believes it is probable that it could incur a loss and has established an estimated legal reserve of $12.0 million related to the ongoing SEC investigation; however, as discussions are continuing, there can be no assurance as to the timing or the terms of any final resolution of this matter. 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.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) The table below sets forth selected unaudited financial data for each quarter of the years ended December 31, 2018 and December 31, 2017 (in millions, except per share amounts): Year Ended December 31, 2018 Year Ended December 31, 2017 First Quarter Second Quarter Third Quarter Fourth Quarter First Quarter Second Quarter Third Quarter Fourth Quarter Net revenues $ 1,082.6 $ 1,204.1 $ 1,179.8 $ 1,181.0 $ 1,221.0 $ 1,308.9 $ 1,257.8 $ 1,239.5 Gross margin 618.4 700.9 711.0 710.9 746.6 801.9 772.4 751.2 Income before income taxes 41.4 150.9 152.0 188.4 140.6 245.2 225.8 200.2 Net income (loss) (1) $ 34.4 $ 116.5 $ 223.8 $ 192.2 $ 108.8 $ 179.8 $ 165.7 $ (148.1 ) Net income (loss) per share: (2) Basic $ 0.10 $ 0.33 $ 0.65 $ 0.56 $ 0.29 $ 0.47 $ 0.44 $ (0.40 ) Diluted (3) $ 0.10 $ 0.33 $ 0.64 $ 0.55 $ 0.28 $ 0.47 $ 0.43 $ (0.40 ) _______________ (1) Net income for the third and fourth quarters of 2018 include a lower statutory tax rate due to the Tax Act and tax benefits related to items unique to 2018. See Note 14, Income Taxes , for further discussion. Net loss for the fourth quarter of 2017 includes an estimated $289.5 million of tax expense related to the Tax Act, and restructuring charges of $36.2 million . (2) Net income (loss) per share is computed independently. Therefore, the sum of the quarterly net income per share may not equal the total computed for the year or any cumulative interim period. (3) Potentially dilutive common shares for the fourth quarter of 2017 were excluded from the computation of diluted net loss per share because their effect would be anti-dilutive.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Restructuring In January 2019, the Company initiated a restructuring plan (the "2019 Restructuring Plan") designed to realign its workforce with the Company's sales strategy, improve productivity, and enhance cost efficiencies. The 2019 Restructuring Plan consists of workforce reductions and facility consolidations and closures. The Company estimates that the implementation of the 2019 Restructuring Plan will result in total charges of approximately $18.0 million to $22.0 million . Dividend Declaration On January 29, 2019 , the Company announced that the Board declared a quarterly cash dividend of $0.19 per share of common stock to be paid on March 22, 2019 to stockholders of record as of the close of business on March 1, 2019 .

Schedule II- Valuation and Qual

Schedule II- Valuation and Qualifying Account	12 Months Ended
	Dec. 31, 2018
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Account	Juniper Networks, Inc. Schedule II - Valuation and Qualifying Accounts Years Ended December 31, 2018 , 2017 , and 2016 (In millions) Allowance for Doubtful Accounts Balance at Beginning of Year Charged to (Reversed from) Costs and Expenses Write-offs, Net of Recoveries Balance at End of Year 2018 $ 5.7 $ (0.8 ) $ — $ 4.9 2017 $ 7.6 $ (2.0 ) $ 0.1 $ 5.7 2016 $ 9.3 $ 1.0 $ (2.7 ) $ 7.6 Additions Sales Return Reserve Balance at Beginning of Year Charged as a Reduction in Revenues Charged to Other Accounts Used Balance at End of Year 2018 (*) $ 44.5 $ 70.7 $ — $ (82.5 ) $ 32.7 2017 $ 71.4 $ 25.0 $ 65.9 $ (107.1 ) $ 55.2 2016 $ 71.2 $ 44.6 $ 89.6 $ (134.0 ) $ 71.4

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates 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 Consolidated Financial Statements and the accompanying notes. The Company bases its estimates and assumptions on current facts, historical experience, and various other factors that it believes are reasonable under the circumstances, to determine the carrying values of assets and liabilities that are not readily apparent from other sources. To the extent there are material differences between the Company's estimates and the actual results, the Company's future consolidated results of operation may be affected.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of cash on hand, demand deposits with banks, highly liquid investments in money market funds, commercial paper, government securities, certificates of deposits, time deposits, and corporate debt securities, which are readily convertible into cash. All highly liquid investments with original maturities of three months or less from Juniper's purchase date are classified as cash equivalents.
Investments in Available-for-Sale Debt Securities and Equity Securities	Investments in Available-for-Sale Debt Securities The Company's investments in debt securities are classified as available-for-sale and include the Company's fixed income securities and investments in privately-held companies, consisting of debt and redeemable preferred stock securities. Fixed income securities are initially recorded at cost and periodically adjusted to fair value in the Consolidated Balance Sheets. Unrealized gains and losses on these investments are reported as a separate component of accumulated other comprehensive loss in the Consolidated Balance Sheets. Realized gains and losses are determined based on the specific identification method and are reported in the Consolidated Statements of Operations. Fixed income securities primarily consist of asset-backed securities, certificate of deposits, commercial paper, corporate debt securities, time deposits, foreign government debt securities, U.S. government agency securities, and U.S. treasury securities. The Company periodically evaluates these investments to determine if impairment charges are required. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value has been less than the Company's cost basis, the investment's financial condition, and the near-term prospects of the investee. If the Company determines that the decline in an investment's value is other than temporary, the difference is recognized as an impairment loss in its Consolidated Statements of Operations. The Company's privately-held debt and redeemable preferred stock securities are included in other long-term assets in the Consolidated Balance Sheets and are recorded at fair value. Fair value is reassessed when the Company is made aware of information indicating a change in the enterprise value of the investee, including known acquisition offers, subsequent funding rounds, and investee's plans for liquidation. The Company periodically evaluates these securities for indicators of impairment, including the inability to recover a portion of or the entire carrying amount of the investment, the inability of the investee to sustain earnings, the reduction in or termination of financial commitment to the investee from other investors, the intention to sell the investment, and whether it is more likely than not that the Company will be required to sell the investment before recovery of the entire amortized cost basis. If the Company determines that the decline in an investment's value is other than temporary, the difference is recognized as an impairment loss in its Consolidated Statements of Operations. Investments in Equity Securities The Company's investments in equity securities with readily determinable fair values consist of money market funds, the non-qualified compensation plan ("NQDC") that is invested in mutual funds, and investments in public companies. These investments are measured at fair value with changes in fair value recognized in the Consolidated Statements of Operations. Equity securities without readily determinable fair values include the Company's investments in privately-held companies consisting of non-redeemable preferred stock and common stock securities. The Company accounts for these securities at cost, adjusted for changes from observable transactions for identical or similar investments of the same issuer, less impairments. Fair value of these equity securities is reassessed when the Company identifies observable price changes indicating that an adjustment upward or downward to the carrying value is necessary. Any observable changes in fair value are recognized in earnings as of the date that the observable transaction took place, rather than the current reporting date. In addition, the Company periodically evaluates equity securities without readily determinable fair values to determine if impairment charges are required by evaluating whether an event or change in circumstance has occurred that may have a significant adverse effect on the fair value of the investment. A qualitative assessment is performed each reporting period to assess whether there are any impairment indicators, including, but not limited to, significant deterioration in the investee's earnings performance; credit rating; asset quality or business prospects; adverse change in the regulatory, economic, or technological environment; change in the general market condition of the geographic area or industry; acquisition offers; and the ability to continue as a going concern. If such indicators are present, the Company estimates the fair value of impaired investments and recognizes an impairment loss in the Consolidated Statement of Operations equal to the difference between the carrying value and fair value.
Fair Value	Fair Value Fair value is defined as the price that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value, the Company considers the principal or most advantageous market in which it transacts, and considers assumptions that market participants would use when pricing the asset or liability. The Company applies the following fair value hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1 – Quoted prices in active markets for identical assets or liabilities. Level 2 – Quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. These inputs are valued using market based approaches. Level 3 – Inputs are unobservable inputs based on the Company’s assumptions. These inputs, if any, are valued using internal financial models.
Derivatives	Derivatives The Company uses derivatives to partially offset its market exposure to fluctuations in certain foreign currencies. The Company does not enter into derivatives for speculative or trading purposes. The Company uses foreign currency forward contracts to hedge certain forecasted foreign currency transactions relating to operating expenses. These derivatives are designated as cash flow hedges. These derivatives are carried at fair value and the effective portion of the derivative's gain or loss is initially reported as a component of accumulated other comprehensive loss, and upon occurrence of the forecasted transaction, is subsequently reclassified into the costs of services or operating expense line item to which the hedged transaction relates. The Company records any ineffectiveness of the hedging instruments in other expense, net, on its Consolidated Statements of Operations. Cash flows from such hedges are classified as operating activities. The Company also uses foreign currency forward contracts to mitigate variability in gains and losses generated from the re-measurement of certain monetary assets and liabilities denominated in non-functional currencies. These derivatives are carried at fair value with changes recorded in other expense, net in the Consolidated Statements of Operations in the same period as the changes in the fair value from the re-measurement of the underlying assets and liabilities. Cash flows from such derivatives are classified as operating activities. The Company presents its derivative assets and derivative liabilities on a gross basis in the Consolidated Balance Sheets. However, under agreements containing provisions on netting with certain counterparties of foreign exchange contracts, subject to applicable requirements, the Company is allowed to net-settle transactions on the same date in the same currency, with a single net amount payable by one party to the other. The Company is neither required to pledge nor entitled to receive cash collateral related to these derivative transactions.
Inventory	Inventory Inventory consists primarily of component parts to be used in the manufacturing process and finished goods in-transit, and is stated at the lower of cost or net realizable value. Cost is computed using standard cost, which approximates actual cost, on a first-in, first-out basis. A charge is recorded to cost of product when inventory is determined to be in excess of anticipated demand or considered obsolete. At the point of loss recognition, a new, lower-cost basis for that inventory is established, and subsequent changes in facts and circumstances do not result in the restoration or increase in the newly established cost basis.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost less accumulated depreciation. Depreciation is calculated using the straight-line method, over the estimated useful lives of the following assets: Estimated Useful Life (years) Computers, equipment, and software 1.5 to 7 Furniture and fixtures 5 to 7 Building and building improvements 7 to 40 Land improvements 10 to 40 Leasehold improvements Lease term, not to exceed 10 years Construction in progress is related to the construction or development of property and equipment that have not yet been placed in service for their intended use.
Goodwill and Other Long-Lived Assets	Goodwill and Other Long-Lived Assets Goodwill represents the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recorded. The excess of the purchase price over the estimated fair value of net assets of businesses acquired in a business combination is recognized as goodwill. Goodwill is tested for impairment annually during the fourth quarter or more frequently if certain circumstances indicate the carrying value of goodwill is impaired. A qualitative assessment is first made to determine whether it is necessary to quantitatively test goodwill for impairment. This initial assessment includes, among others, consideration of macroeconomic conditions and financial performance. If the qualitative assessment indicates that it is more likely than not that an impairment exists, a quantitative analysis is performed by determining the fair value of each reporting unit using a combination of the income approach and the market approach. Based on the outcome of the quantitative assessments, the Company compares the estimated fair value of each reporting unit with their respective carrying values, including goodwill. An impairment loss is recognized to the extent that the carrying amount of goodwill exceeds the asset's implied fair value. Other intangible assets acquired in a business combination related to in-process research and development ("IPR&D") projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. Indefinite-lived intangibles are not amortized into the results of operations but instead are evaluated for impairment. If and when development is complete, the associated assets would be deemed finite-lived and would be amortized as cost of revenues over their respective estimated useful lives at that point in time. If the research and development project is abandoned, the acquired IPR&D assets are written off and charged to expense in the period of abandonment. Long-lived assets, such as property, plant, and equipment, and purchased intangible assets subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset, or asset group, to estimated undiscounted future cash flows expected to be generated by the asset, or asset group. An impairment charge is recognized by the amount by which the carrying amount of the asset, or asset group, exceeds its fair value. The Company amortizes intangible assets with estimable useful lives on a straight-line basis over their useful lives.
Revenue Recognition	Revenue Recognition 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 by following a five-step process, (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price, and (5) recognize revenue when or as the Company satisfies a performance obligation, as further described below. Identify the contract with a customer . The Company generally considers a sales contract or agreement with an approved purchase order as a customer contract provided that collection is considered probable, which is assessed based on the creditworthiness of the customer as determined by credit checks, payment histories, and/or other circumstances. The Company combines contracts with a customer if contracts are negotiated with a single commercial substance or contain price dependencies. Identify the performance obligations in the contract . Product performance obligations include hardware and software licenses and service performance obligations include maintenance, software post-contract support, training, and professional services. Certain software licenses and related post-contract support are combined into a single performance obligation when the maintenance updates are critical to the continued functionality of the software. Determine the transaction price . The transaction price for the Company’s contracts with its customers consists of both fixed and variable consideration provided it is probable that a significant reversal of revenue will not occur when the uncertainty related to variable consideration is resolved. Fixed consideration includes amounts to be contractually billed to the customer while variable consideration includes estimates for rights of return, rebates, and price protection, which are based on historical sales returns and price protection credits, specific criteria outlined in rebate agreements, and other factors known at the time. The Company generally invoices customers for hardware, software licenses and related maintenance arrangements at time of delivery, and professional services either upfront or upon meeting certain milestones. Customer invoices are generally due within 30 to 90 days after issuance. The Company’s contracts with customers typically do not include significant financing components as the period between the transfer of performance obligations and timing of payment are generally within one year. Allocate the transaction price to the performance obligations in the contract . For contracts that contain multiple performance obligations, the Company allocates the transaction price to the performance obligations on a relative standalone selling price basis. Standalone selling prices are based on multiple factors including, but not limited to historical discounting trends for products and services, pricing practices in different geographies and through different sales channels, gross margin objectives, internal costs, competitor pricing strategies, and industry technology lifecycles. Recognize revenue when or as the Company satisfies a performance obligation . Revenue for hardware and certain software licenses, are recognized at a point in time, which is generally upon shipment or delivery. Certain software licenses combined with post-contract support are recognized over time on a ratable basis over the term of the license. Revenue for maintenance and software post-contract support is recognized over time on a ratable basis over the contract term. Revenue from training and professional services is recognized over time as services are completed or ratably over the contractual period of generally one year or less. Deferred Commissions Sales commissions earned by the Company’s sales force are considered incremental and recoverable costs of obtaining a contract with a customer. These costs are deferred and then amortized over a period of benefit which is typically over the term of the customer contracts as initial commission rates and renewal rates are the same. Amortization expense is included in sales and marketing expenses in the accompanying Consolidated Statements of Operations.
Allowance For Doubtful Accounts	Allowance for Doubtful Accounts The allowance for doubtful accounts is based on the Company's assessment of the collectability of customer accounts. The Company regularly reviews its receivables that remain outstanding past their applicable payment terms and establishes an allowance by considering factors such as historical experience, credit quality, and age of the accounts receivable balances, and current economic conditions that may affect a customer's ability to pay.
Warranty Reserves	Warranty Reserves The Company generally offers a one -year warranty on most of its hardware products, and a 90 -day warranty on the media that contains the software embedded in the products. Warranty costs are recognized as part of the Company's cost of sales based on associated material costs, logistics costs, labor costs, and overhead at the time revenue is recognized. Material costs are estimated primarily based upon the historical costs to repair or replace product returns within the warranty period. Labor, logistics and overhead costs are estimated primarily based upon historical trends in the cost to support customer cases within the warranty period.
Contract Manufacturer Liabilities	Contract Manufacturer Liabilities The Company establishes a liability for non-cancelable, non-returnable purchase commitments with its contract manufacturers for carrying charges, quantities in excess of its demand forecasts, or obsolete material charges for components purchased by the contract manufacturers to meet the Company’s demand forecast or customer orders. The demand forecasts are based upon historical trends and analysis from the Company's sales and marketing organizations, adjusted for overall market conditions.
Research and Development	Research and Development Costs to research, design, and develop the Company's products are expensed as incurred.
Software Development Costs	Software Development Costs Capitalization of software development costs for software to be sold, leased, or otherwise marketed begins when a product's technological feasibility has been established and ends when a product is available for general release to customers. Generally, the Company's products are released soon after technological feasibility has been established. As a result, costs incurred between achieving technological feasibility and product general availability have not been significant. The Company capitalizes costs associated with internal-use software systems during the application development stage. Such capitalized costs include external direct costs incurred in developing or obtaining the applications and payroll and payroll-related costs for employees, who are directly associated with the development of the applications.
Advertising	Advertising Advertising costs are charged to sales and marketing expense as incurred.
Foreign Currency	Foreign Currency Assets and liabilities of foreign operations with non-U.S. Dollar functional currency are translated to U.S. Dollars using exchange rates in effect at the end of the period. Revenue and expenses are translated to U.S. Dollars using rates that approximate those in effect during the period. The resulting translation adjustments are included in the Company’s Consolidated Balance Sheets in the stockholders’ equity section as a component of accumulated other comprehensive loss. The Company records foreign exchange transaction gains and losses for assets and liabilities denominated in non-functional currencies. These remeasurement adjustments are recorded in other expense, net in the Consolidated Statements of Operations.
Loss Contingencies	Loss Contingencies The Company is subject to the possibility of various loss contingencies arising in the ordinary course of business. Management considers the likelihood of loss related to an asset, or the incurrence of a liability, as well as its ability to reasonably estimate the amount of loss, in determining loss contingencies. An estimated loss contingency is accrued when it is probable that an asset has been impaired or a liability has been incurred and the amount of loss can be reasonably estimated. The Company regularly evaluates current information available to determine whether such accruals should be adjusted and whether new accruals are required.
Share-Based Compensation	Share-Based Compensation The Company measures and recognizes compensation cost for all share-based awards made to employees and directors, including employee stock options, restricted stock awards ("RSAs"), restricted stock units ("RSUs"), performance share awards ("PSAs") and employee stock purchases related to the Employee Stock Purchase Plan ("ESPP"). For service condition only awards, share-based compensation expense is based on the fair value of the underlying awards and amortized on a straight-line basis. For PSAs and market-based RSUs, share-based compensation expense is amortized on a straight-line basis for each separate vesting portion of the awards. The Company accounts for forfeitures as they occur. The Company utilizes the Black-Scholes-Merton (“BSM”) option-pricing model to estimate the fair value of its ESPP purchase rights. The BSM model requires various highly subjective assumptions that represent management's best estimates of volatility, risk-free interest rate, expected life, and dividend yield. The Company estimates expected volatility based on the implied volatility of market-traded options, on the Company's common stock, adjusted for other relevant factors including historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected life of the Company’s ESPP. The expected life of ESPP purchase rights approximates the offering period. The Company determines the grant date fair value of its RSUs, RSAs, and PSAs based on the closing market price of the Company’s common stock on the date of grant, adjusted by the present value of the 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. For market-based RSUs, the Company estimates the fair value and derived service period using the Monte Carlo simulation option pricing model ("Monte Carlo model"). The determination of the grant date fair value and derived service periods using the Monte Carlo model is affected by the Company's stock price, comparative market-based returns, as well as various highly subjective assumptions that represent management's best estimates of volatility, risk-free interest rate, and dividend yield. The Company estimates expected volatility based on the implied volatility of market-traded options, on the Company's common stock, adjusted for other relevant factors including historical volatility of the Company’s common stock over the contractual life of the Company's market-based RSUs.
Provision for Income Taxes	Provision for Income Taxes Deferred tax assets and liabilities are recognized for the expected tax consequences of temporary differences between the tax bases of assets and liabilities and their reported amounts. Valuation allowances are recorded to reduce deferred tax assets to the amount that will more likely than not be realized. The Company accounts for uncertainty in income taxes using a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon settlement. The Company classifies the liability for unrecognized tax benefits as current to the extent that the Company anticipates payment (or receipt) of cash within one year . Interest and penalties related to uncertain tax positions are recognized in the provision for income taxes.
Concentrations of Risk	Concentrations of Risk Financial instruments that subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, investments, derivatives, and accounts receivable. The Company invests only in high-quality credit instruments and maintains its cash, cash equivalents and available-for-sale investments in fixed income securities with several high-quality institutions. Deposits held with banks, including those held in foreign branches of global banks, may exceed the amount of insurance provided on such deposits. We mitigate the concentration of credit risk in our investment portfolio through diversification of the investments in various industries and asset classes, and limits to the amount of credit exposure to any single issuer and credit rating. The Company’s derivatives expose it to credit risk to the extent that counterparties may be unable to meet the terms of the agreement. To mitigate concentration of risk related to its derivatives, the Company establishes counterparty limits to major credit-worthy financial institutions. In addition, the potential risk of loss with any one counterparty resulting from this type of credit risk is monitored and the derivatives transacted with these entities are relatively short in duration. Therefore, the Company does not expect material losses as a result of defaults by counterparties. Generally, credit risk with respect to accounts receivable is diversified due to the number of entities comprising the Company's customer base and their dispersion across different geographic locations throughout the world. The Company performs ongoing credit evaluations of its customers and generally does not require collateral on accounts receivable. During the years ended December 31, 2018 , 2017 , and 2016 , no single customer accounted for 10% or more of net revenues. The Company relies on sole suppliers for certain of its components such as application-specific integrated circuits ("ASICs") and custom sheet metal. Additionally, the Company relies primarily on a limited number of significant independent contract manufacturers and original design manufacturers for the production of its products. The inability of any supplier or manufacturer to fulfill supply requirements of the Company could negatively impact future operating results.
Recently Adopted Accounting Standard and Recent Accounting Standards Not Yet Adopted	Recently Adopted Accounting Standard Comprehensive Income: Effective January 1, 2018, the Company early adopted FASB ASU No. 2018-02 (Topic 220), Income Statement - Reporting Comprehensive Income , issued in February 2018, with an election to reclassify stranded tax effects resulting from the U.S. Tax Cuts and Jobs Act (the "Tax Act"), from accumulated other comprehensive income to retained earnings. The adoption resulted in a reclassification of $5.7 million in income from accumulated other comprehensive loss to accumulated deficit as of the adoption date. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. Financial Instruments: On January 1, 2018, the Company adopted FASB ASU No. 2016-01, Financial Instruments—Overall: Recognition and Measurement of Financial Assets and Financial Liabilities and FASB ASU No. 2018-03, Technical Corrections and Improvements to Financial Instruments - Overall , which changes how entities classify and 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. The Company adopted ASU 2016-01 as of January 1, 2018 using the modified retrospective method for its equity securities with readily determinable fair values and the prospective method for its equity securities without readily determinable fair values, resulting in no impact to the opening accumulated deficit balance. The Company has elected to use the measurement alternative for its equity investments without readily determinable fair value, defined as cost adjusted for changes from observable transactions for identical or similar investments of the same issuer, less impairment. See Note 4, Cash Equivalents and Investments for additional disclosures required upon adopting the standard. Revenue Recognition: On January 1, 2018, the Company adopted FASB ASU No. 2014-09 (Topic 606) - Revenue from Contracts with Customers (“ASU 2014-09” or "Topic 606"), which provides guidance for revenue recognition that superseded the revenue recognition requirements in Accounting Standards Codification ("ASC") Topic 605, Revenue Recognition ("Topic 605") and most industry specific guidance. Under ASU 2014-09, 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. The Company adopted ASU 2014-09 under the modified retrospective approach, applying the amendments to prospective reporting periods. Results for reporting periods beginning after January 1, 2018 are presented under Topic 606, while prior period amounts are not adjusted and continue to be reported in accordance with the historic accounting under Topic 605. The cumulative effect of the changes made to the Company's Consolidated Balance Sheet as of January 1, 2018 for the adoption of Topic 606 to all contracts with customers that were not completed as of December 31, 2017 was recorded as an adjustment to accumulated deficit as of the adoption date as follows: December 31, 2017 January 1, 2018 As reported Adjustments As adjusted Assets: Accounts receivable, net of allowances $ 852.0 $ (1.9 ) $ 850.1 Prepaid expenses and other current assets 299.9 31.5 331.4 Other long-term assets 415.5 (21.1 ) 394.4 Total assets $ 9,833.8 $ 8.5 $ 9,842.3 Liabilities: Deferred revenue $ 1,030.3 $ (225.4 ) $ 804.9 Other accrued liabilities 304.3 33.8 338.1 Long-term deferred revenue 509.0 (124.6 ) 384.4 Total liabilities $ 5,152.9 $ (316.2 ) $ 4,836.7 Stockholders' Equity: Accumulated deficit $ (3,355.8 ) $ 324.7 $ (3,031.1 ) Upon adoption, the Company recorded a cumulative effect adjustment of $324.7 million , net of tax adjustment of $63.9 million , which decreased the January 1, 2018 opening accumulated deficit balance on the Consolidated Balance Sheet, primarily as a result of the following items: • Distributor Sales : Under Topic 606, the Company recognizes revenue from sales to distributors upon delivery of the product to the distributor, rather than upon delivery of the product to the end-customer. Rebates and incentives offered to distributors, which are earned when sales to end-customers are completed, are estimated at the point of revenue recognition. • Software Revenue : Under Topic 605, the Company deferred revenue for software licenses where vendor-specific objective evidence of fair value had not been established for undelivered items (primarily services). Under Topic 606, revenue for software licenses is recognized at the time of delivery unless the ongoing services provide frequent, critical updates to the software, without which the software functionality would be rapidly diminished. • Variable Consideration : Some of the Company's contracts include penalties, extended payment terms, acceptance provisions or other price variability that precluded revenue recognition under Topic 605 because of the requirement for amounts to be fixed or determinable. Topic 606 requires the Company to estimate and account for variable consideration as a reduction of the transaction price. • Revenue Allocation : Similar to Topic 605, Topic 606 requires an allocation of revenue between deliverables, or performance obligations, within an arrangement. Topic 605 restricted the allocation of revenue that is contingent on future deliverables to current deliverables; however, Topic 606 removes this restriction. In addition, the nature of the performance obligations identified within a contract under Topic 606 as compared to Topic 605 will impact the allocation of the transaction price between product and services. • Contract Acquisition Costs : Topic 606 requires the deferral and amortization of “incremental” costs incurred to obtain a contract where the associated contract duration is greater than one year. The primary contract acquisition cost for the Company are sales commissions. Prior to January 1, 2018, the Company expensed sales commissions. The change required by Topic 606 resulted in the creation of an asset on January 1, 2018. The impact of the adoption of Topic 606 on the Company's Consolidated Statements of Operations and Consolidated Balance Sheet was as follows (in millions): Year Ended December 31, 2018* As Reported Without Adoption of Topic 606 Topic 606 Impact Net revenues: Product $ 3,107.1 $ 3,006.8 $ 100.3 Service 1,540.4 1,663.3 (122.9 ) Total net revenues $ 4,647.5 $ 4,670.1 $ (22.6 ) Operating expenses: Sales and marketing $ 927.4 $ 929.3 $ (1.9 ) ________________________________ * Except as disclosed, the adoption of Topic 606 did not have a material impact on the Company’s Consolidated Statements of Operations for the year ended December 31, 2018. As of December 31, 2018 As Reported Without Adoption of Topic 606 Topic 606 Impact Assets: Accounts receivable, net of allowances $ 754.6 $ 746.3 $ 8.3 Prepaid expenses and other current assets 268.1 241.6 26.5 Other long-term assets 403.5 400.4 3.1 Total assets $ 9,363.3 $ 9,325.6 $ 37.7 Liabilities: Deferred revenue $ 829.3 $ 1,111.9 $ (282.6 ) Other accrued liabilities 233.5 178.6 54.9 Long-term deferred revenue 384.3 431.8 (47.5 ) Total liabilities $ 4,540.1 $ 4,815.2 $ (275.1 ) Stockholders' Equity: Accumulated deficit $ (2,831.4 ) $ (3,144.3 ) $ 312.9 Recent Accounting Standards Not Yet Adopted Cloud Computing Arrangement: In August 2018, the FASB issued ASU No. 2018-15 (Subtopic 350-40) Intangibles — Goodwill and Other-Internal-Use Software: Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which provides guidance on a customer's accounting for implementation, set-up, and other upfront costs incurred in a cloud computing arrangement that is hosted by a service contract. The new standard is to be applied on either a retrospective or prospective basis to all implementation costs incurred after the date of adoption. The standard is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted. The Company early adopted the standard effective January 1, 2019 and will prospectively apply the standard to all implementation costs incurred after the adoption date. Fair Value Measurement: In August 2018, the FASB issued ASU No. 2018-13 (Topic 820) Disclosure Framework — Changes to the Disclosure Requirements for Fair Value Measurement, which eliminates, adds, and modifies certain disclosure requirements for fair value measurements under ASC 820. This ASU is to be applied on a prospective basis for certain modified or new disclosure requirements, and all other amendments in the standard are to be applied on a retrospective basis. The new standard is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted. The Company is currently evaluating the impact of adoption on the Consolidated Financial Statements. Derivatives and Hedging: In August 2017, the FASB issued ASU No. 2017-12 (Topic 815) Derivatives and Hedging — Targeted Improvements to Accounting for Hedging Activities , and an amendment thereafter, 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 its amendment and presentation and disclosure requirements will be applied on a prospective basis. This standard along with its amendment is effective for interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company does not expect the adoption to have a material impact on the Consolidated Financial Statements. Amortization on Purchased Callable Debt Securities: 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 adoption of this standard will not have an impact on the Consolidated Financial Statements. Simplifying the Test for Goodwill Impairment: 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. The Company does not expect the adoption to have a material impact on the Consolidated Financial Statements. Credit Losses on Financial Instruments: 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. Further amendment issued by the FASB in November 2018 clarifies that receivables arising from operating leases are not within the scope of Topic 326 and should be accounted for in accordance with Topic 842. This pronouncement and its amendment are 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 of adoption on the Consolidated Financial Statements. Leases: In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases , and several amendments thereafter, which require recognition of right-of-use ("ROU") assets and lease liabilities for most leases on the Consolidated Balance Sheets by lessees. The guidance also requires enhanced disclosures. The ASU is effective for annual reporting periods beginning after December 15, 2018. The Company has adopted the standard on January 1, 2019 under the modified retrospective approach. Upon adoption, the Company elected: • the package of practical expedients which allows for not reassessing (1) whether existing contracts contain leases, (2) the lease classification for existing leases, and (3) whether existing initial direct costs meet the new definition. • the practical expedient in ASC Subtopic 842-10 to not separate non-lease components from lease components and instead account for each separate lease component and non-lease components associated with that lease component as a single lease component by class of the underlying asset. • not to recognize ROU assets and lease liabilities for short-term leases, which have a lease term of twelve months or less and do not include an option to purchase the underlying asset that the Company is reasonably certain to exercise. The adoption of the standard resulted in recognition of ROU assets and lease liabilities of approximately $200.0 million and $230.0 million , respectively, on the Company's Consolidated Balance Sheets, primarily relating to real estate operating leases. The adoption of the standard did not result in a material impact on the Company's Consolidated Statements of Operations. Additionally, the adoption of the standard had no impact on the Company’s debt-covenant compliance under its current agreements.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]	The cumulative effect of the changes made to the Company's Consolidated Balance Sheet as of January 1, 2018 for the adoption of Topic 606 to all contracts with customers that were not completed as of December 31, 2017 was recorded as an adjustment to accumulated deficit as of the adoption date as follows: December 31, 2017 January 1, 2018 As reported Adjustments As adjusted Assets: Accounts receivable, net of allowances $ 852.0 $ (1.9 ) $ 850.1 Prepaid expenses and other current assets 299.9 31.5 331.4 Other long-term assets 415.5 (21.1 ) 394.4 Total assets $ 9,833.8 $ 8.5 $ 9,842.3 Liabilities: Deferred revenue $ 1,030.3 $ (225.4 ) $ 804.9 Other accrued liabilities 304.3 33.8 338.1 Long-term deferred revenue 509.0 (124.6 ) 384.4 Total liabilities $ 5,152.9 $ (316.2 ) $ 4,836.7 Stockholders' Equity: Accumulated deficit $ (3,355.8 ) $ 324.7 $ (3,031.1 ) The impact of the adoption of Topic 606 on the Company's Consolidated Statements of Operations and Consolidated Balance Sheet was as follows (in millions): Year Ended December 31, 2018* As Reported Without Adoption of Topic 606 Topic 606 Impact Net revenues: Product $ 3,107.1 $ 3,006.8 $ 100.3 Service 1,540.4 1,663.3 (122.9 ) Total net revenues $ 4,647.5 $ 4,670.1 $ (22.6 ) Operating expenses: Sales and marketing $ 927.4 $ 929.3 $ (1.9 ) ________________________________ * Except as disclosed, the adoption of Topic 606 did not have a material impact on the Company’s Consolidated Statements of Operations for the year ended December 31, 2018. As of December 31, 2018 As Reported Without Adoption of Topic 606 Topic 606 Impact Assets: Accounts receivable, net of allowances $ 754.6 $ 746.3 $ 8.3 Prepaid expenses and other current assets 268.1 241.6 26.5 Other long-term assets 403.5 400.4 3.1 Total assets $ 9,363.3 $ 9,325.6 $ 37.7 Liabilities: Deferred revenue $ 829.3 $ 1,111.9 $ (282.6 ) Other accrued liabilities 233.5 178.6 54.9 Long-term deferred revenue 384.3 431.8 (47.5 ) Total liabilities $ 4,540.1 $ 4,815.2 $ (275.1 ) Stockholders' Equity: Accumulated deficit $ (2,831.4 ) $ (3,144.3 ) $ 312.9
Property and equipment useful life	Depreciation is calculated using the straight-line method, over the estimated useful lives of the following assets: Estimated Useful Life (years) Computers, equipment, and software 1.5 to 7 Furniture and fixtures 5 to 7 Building and building improvements 7 to 40 Land improvements 10 to 40 Leasehold improvements Lease term, not to exceed 10 years

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Schedule of estimated fair values of assets acquired and liabilities assumed	The following table summarizes the fair values of the assets acquired and liabilities assumed at the acquisition dates (in millions): 2018 2017 2016 HTBase (1) Cyphort (2) AppFormix Aurrion BTI (2) Net tangible assets acquired/(liabilities) assumed $ (1.0 ) $ 1.4 $ (5.3 ) $ 6.0 $ (19.7 ) Intangible assets 7.8 15.4 20.3 49.0 43.3 Goodwill (3) 14.4 16.7 32.9 46.9 20.2 Total $ 21.2 $ 33.5 $ 47.9 $ 101.9 $ 43.8 ________________________________ (1) The primary areas of the preliminary purchase price allocation that are subject to change relate to certain legal and income tax matters. (2) See Note 7, Goodwill and Purchased Intangible Assets , for adjustments made during the measurement period subsequent to the acquisition dates. (3) The goodwill recognized for these acquisitions was primarily attributable to expected synergies and is not deductible for U.S. federal income tax purposes.
Summary of fair value of separately identifiable intangible assets acquired	The following table summarizes the fair value of the separately identifiable intangible assets at the time of acquisition and the period over which each intangible asset will be amortized (in millions, except years): 2018 2017 2016 HTBase Cyphort AppFormix Aurrion BTI Weighted Amount Weighted Amount Weighted Average Estimated Useful Life (In Years) Amount Weighted Average Estimated Useful Life (In Years) Amount Weighted Average Estimated Useful Life (In Years) Amount Finite-lived intangible assets: Existing technology 4 $ 7.8 5 $ 15.4 5 $ 20.1 — $ — 8 $ 37.1 Customer relationships — — — — 1 0.2 — — 8 5.3 Other — — — — — — — — 1 0.9 Total intangible assets with finite lives 7.8 15.4 20.3 — 43.3 Indefinite-lived intangible assets: IPR&D — — — 49.0 — Total intangible assets acquired $ 7.8 $ 15.4 $ 20.3 $ 49.0 $ 43.3

Cash Equivalents and Investme_2

Cash Equivalents and Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Cash Equivalents and Investments [Abstract]
Unrealized gains and losses and fair value of available-for-sale debt securities	The following table summarizes the Company's unrealized gains and losses and fair value of investments designated as available-for-sale debt securities as of December 31, 2018 and December 31, 2017 (in millions): As of December 31, 2018 As of December 31, 2017 Amortized Gross Unrealized Gross Unrealized Estimated Fair Amortized Gross Unrealized Gross Unrealized Estimated Fair Fixed income securities: Asset-backed securities $ 46.8 $ — $ (0.3 ) $ 46.5 $ 287.1 $ — $ (0.6 ) $ 286.5 Certificates of deposit 152.9 — — 152.9 83.8 — — 83.8 Commercial paper 393.6 — — 393.6 217.1 — — 217.1 Corporate debt securities 416.1 — (3.1 ) 413.0 929.6 0.4 (3.0 ) 927.0 Foreign government debt securities 20.0 — (0.1 ) 19.9 62.9 — (0.2 ) 62.7 Time deposits 278.6 — — 278.6 239.2 — — 239.2 U.S. government agency securities 87.2 — (0.2 ) 87.0 143.9 — (0.7 ) 143.2 U.S. government securities 811.8 — (0.5 ) 811.3 406.8 0.1 (0.9 ) 406.0 Total fixed income securities 2,207.0 — (4.2 ) 2,202.8 2,370.4 0.5 (5.4 ) 2,365.5 Privately-held debt and redeemable preferred stock securities 16.6 37.4 — 54.0 15.9 37.4 — 53.3 Total available-for-sale debt securities $ 2,223.6 $ 37.4 $ (4.2 ) $ 2,256.8 $ 2,386.3 $ 37.9 $ (5.4 ) $ 2,418.8 Reported as: Cash equivalents $ 936.5 $ — $ — $ 936.5 $ 351.0 $ — $ — $ 351.0 Short-term investments 1,069.2 — (1.9 ) 1,067.3 1,027.2 0.1 (1.2 ) 1,026.1 Long-term investments 201.3 — (2.3 ) 199.0 992.2 0.4 (4.2 ) 988.4 Other long-term assets 16.6 37.4 — 54.0 15.9 37.4 — 53.3 Total $ 2,223.6 $ 37.4 $ (4.2 ) $ 2,256.8 $ 2,386.3 $ 37.9 $ (5.4 ) $ 2,418.8
Maturities of fixed income securities	The following table presents the contractual maturities of the Company's total fixed income securities as of December 31, 2018 (in millions): Amortized Cost Estimated Fair Value Due in less than one year $ 2,005.7 $ 2,003.8 Due between one and five years 201.3 199.0 Total $ 2,207.0 $ 2,202.8
Available-for-sale investments in an unrealized loss position	The following tables present the Company's total fixed income securities that were in an unrealized loss position as of December 31, 2018 and December 31, 2017 (in millions): As of December 31, 2018 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 $ 3.1 $ — $ 43 $ (0.3 ) $ 46.1 $ (0.3 ) Corporate debt securities 72.6 (0.1 ) 330.7 (3.0 ) 403.3 (3.1 ) Foreign government debt securities 1.5 — 18.4 (0.1 ) 19.9 (0.1 ) U.S. government agency securities 2.0 — 45.2 (0.2 ) 47.2 (0.2 ) U.S. government securities 344.0 — 63.5 (0.5 ) 407.5 (0.5 ) Total fixed income securities $ 423.2 $ (0.1 ) $ 500.8 $ (4.1 ) $ 924.0 $ (4.2 ) As of December 31, 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 $ 215.2 $ (0.4 ) $ 38.4 $ (0.2 ) $ 253.6 $ (0.6 ) Corporate debt securities 646.7 (2.1 ) 108.6 (0.9 ) 755.3 (3.0 ) Foreign government debt securities 47.3 (0.2 ) 6.6 — 53.9 (0.2 ) U.S. government agency securities 68.3 (0.2 ) 67.9 (0.5 ) 136.2 (0.7 ) U.S. government securities 260.8 (0.7 ) 51.8 (0.2 ) 312.6 (0.9 ) Total fixed income securities $ 1,238.3 $ (3.6 ) $ 273.3 $ (1.8 ) $ 1,511.6 $ (5.4 )
Schedule of investments in equity securities	The following table presents the Company's investments in equity securities as of December 31, 2018 and 2017 (in millions): As of December 31, 2018 2017 Equity investments with readily determinable fair value Money market funds (1) $ 996.9 $ 969.8 Mutual funds (2) 24.3 27.6 Publicly-traded equity securities 2.8 — Equity investments without readily determinable fair value (3) 36.4 29.7 Total equity securities $ 1,060.4 $ 1,027.1 Reported as: Cash equivalents $ 985.3 $ 928.0 Short-term investments 2.8 — Prepaid expenses and other current assets 10.9 36.3 Other long-term assets 61.4 62.8 Total $ 1,060.4 $ 1,027.1 ________________________________ (1) Prior to January 1, 2018, money market funds were classified as available-for-sale securities and accounted for at fair value with unrealized gains and losses recognized in accumulated other comprehensive income (loss). Realized gains or losses from sales or impairments were recognized in the Consolidated Statements of Operations. (2) Prior to January 1, 2018, mutual funds related to the Company's NQDC plan were classified as trading securities. Unrealized gains or losses were recognized in the Consolidated Statements of Operations. (3) Prior to January 1, 2018, certain investments in privately-held companies were accounted for at cost less impairment. Realized gains or losses from sales or impairments were recognized in the Consolidated Statements of Operations.
Schedule of reconciliation of cash, cash equivalents and restricted cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash included in the Consolidated Balance Sheets as of December 31, 2018 and December 31, 2017 (in millions): As of December 31, 2018 2017 Cash and cash equivalents $ 2,489.0 $ 2,006.5 Restricted cash included in Prepaid expenses and other current assets 16.8 49.6 Restricted cash included in Other long-term assets — 3.0 Total cash, cash equivalents, and restricted cash $ 2,505.8 $ 2,059.1

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
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 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 debt securities: Asset-backed securities $ — $ 46.5 $ — $ 46.5 $ — $ 286.5 $ — $ 286.5 Certificates of deposit — 152.9 — 152.9 — 83.8 — 83.8 Commercial paper — 393.6 — 393.6 — 217.1 — 217.1 Corporate debt securities — 413.0 — 413.0 — 927.0 — 927.0 Foreign government debt securities — 19.9 — 19.9 — 62.7 — 62.7 Time deposits — 278.6 — 278.6 — 239.2 — 239.2 U.S. government agency securities — 87.0 — 87.0 — 143.2 — 143.2 U.S. government securities 352.8 458.5 — 811.3 322.4 83.6 — 406.0 Privately-held debt and redeemable preferred stock securities — — 54.0 54.0 — — 53.3 53.3 Total available-for-sale debt securities 352.8 1,850.0 54.0 2,256.8 322.4 2,043.1 53.3 2,418.8 Equity securities: Money market funds (1) 996.9 — — 996.9 969.8 — — 969.8 Mutual funds (2) 24.3 — — 24.3 27.6 — — 27.6 Publicly-traded equity securities 2.8 — — 2.8 — — — — Total equity securities 1,024.0 — — 1,024.0 997.4 — — 997.4 Derivative assets: Foreign exchange contracts — 5.3 — 5.3 — 9.2 — 9.2 Total assets measured at fair value $ 1,376.8 $ 1,855.3 $ 54.0 $ 3,286.1 $ 1,319.8 $ 2,052.3 $ 53.3 $ 3,425.4 Liabilities: Derivative liabilities: Foreign exchange contracts $ — $ (7.1 ) $ — $ (7.1 ) $ — $ (1.8 ) $ — $ (1.8 ) Total liabilities measured at fair value $ — $ (7.1 ) $ — $ (7.1 ) $ — $ (1.8 ) $ — $ (1.8 ) Total assets, reported as: Cash equivalents $ 1,025.2 $ 896.6 $ — $ 1,921.8 $ 928.1 $ 350.9 $ — $ 1,279.0 Short-term investments 297.5 772.6 — 1,070.1 247.5 778.6 — 1,026.1 Long-term investments 18.2 180.8 — 199.0 74.8 913.6 — 988.4 Prepaid expenses and other current assets 10.8 5.3 — 16.1 36.3 9.2 — 45.5 Other long-term assets 25.1 — 54.0 79.1 33.1 — 53.3 86.4 Total assets measured at fair value $ 1,376.8 $ 1,855.3 $ 54.0 $ 3,286.1 $ 1,319.8 $ 2,052.3 $ 53.3 $ 3,425.4 Total liabilities, reported as: Other accrued liabilities $ — $ (7.1 ) $ — $ (7.1 ) $ — $ (1.8 ) $ — $ (1.8 ) Total liabilities measured at fair value $ — $ (7.1 ) $ — $ (7.1 ) $ — $ (1.8 ) $ — $ (1.8 ) ________________________________ (1) Balance includes $11.6 million and $16.8 million in restricted investments measured at fair value, related to the Company's acquisition-related escrows for the years ended December 31, 2018 and 2017 , respectively. The December 31, 2017 balance also includes $25.0 million related to the Company's Directors and Officers indemnification trust, which was subsequently terminated. (2) Balance relates to restricted investments measured at fair value related to the Company's NQDC plan.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments	The notional amount of the Company's foreign currency derivatives is summarized as follows (in millions): As of December 31, 2018 2017 Cash flow hedges $ 497.7 $ 521.1 Non-designated derivatives 158.7 108.3 Total $ 656.4 $ 629.4

Goodwill and Purchased Intang_2

Goodwill and Purchased Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	The Company's goodwill activity was as follows (in millions): Total December 31, 2016 $ 3,081.7 Additions due to business combination 16.7 Other (*) (2.2 ) December 31, 2017 3,096.2 Additions due to business combination 14.4 Other (*) (1.8 ) December 31, 2018 $ 3,108.8 ________________________________ (*) Other primarily consists of certain purchase accounting adjustments related to the acquisitions of BTI and Cyphort.
Schedule of Acquired Indefinite-Lived Intangible Assets by Major Class	The Company’s purchased intangible assets, net, were as follows (in millions): As of December 31, 2018 As of December 31, 2017 Gross Accumulated Accumulated Impairments and Net Gross Accumulated Accumulated Impairments and Net Finite-lived intangible assets: Technologies and patents $ 648.1 $ (534.0 ) $ (49.9 ) $ 64.2 $ 640.3 $ (518.1 ) $ (49.9 ) $ 72.3 Customer contracts, support agreements, and related relationships 83.6 (75.5 ) (2.8 ) 5.3 83.6 (74.1 ) (2.8 ) 6.7 Other 2.0 (2.0 ) — — 2.0 (1.9 ) — 0.1 Total 733.7 (611.5 ) (52.7 ) 69.5 725.9 (594.1 ) (52.7 ) 79.1 Indefinite-lived intangible assets: IPR&D 49.0 — — 49.0 49.0 — — 49.0 Total purchased intangible assets $ 782.7 $ (611.5 ) $ (52.7 ) $ 118.5 $ 774.9 $ (594.1 ) $ (52.7 ) $ 128.1
Schedule of Acquired Finite-Lived Intangible Assets by Major Class	The Company’s purchased intangible assets, net, were as follows (in millions): As of December 31, 2018 As of December 31, 2017 Gross Accumulated Accumulated Impairments and Net Gross Accumulated Accumulated Impairments and Net Finite-lived intangible assets: Technologies and patents $ 648.1 $ (534.0 ) $ (49.9 ) $ 64.2 $ 640.3 $ (518.1 ) $ (49.9 ) $ 72.3 Customer contracts, support agreements, and related relationships 83.6 (75.5 ) (2.8 ) 5.3 83.6 (74.1 ) (2.8 ) 6.7 Other 2.0 (2.0 ) — — 2.0 (1.9 ) — 0.1 Total 733.7 (611.5 ) (52.7 ) 69.5 725.9 (594.1 ) (52.7 ) 79.1 Indefinite-lived intangible assets: IPR&D 49.0 — — 49.0 49.0 — — 49.0 Total purchased intangible assets $ 782.7 $ (611.5 ) $ (52.7 ) $ 118.5 $ 774.9 $ (594.1 ) $ (52.7 ) $ 128.1
Estimated Future Amortization Expense of Purchased Intangible Assets with Finite Lives	As of December 31, 2018 , the estimated future amortization expense of purchased intangible assets with finite lives is as follows (in millions): Years Ending December 31, Amount 2019 $ 25.1 2020 17.2 2021 12.9 2022 7.7 2023 5.3 Thereafter 1.3 Total $ 69.5

Other Financial Information (Ta

Other Financial Information (Tables)	12 Months Ended
	Dec. 31, 2018
Other Financial Information [Abstract]
Inventories	Total inventory consisted of the following (in millions): As of December 31, 2018 2017 Production and service materials $ 60.6 $ 71.2 Finished goods 21.4 26.6 Inventory $ 82.0 $ 97.8 Reported as: Prepaid expenses and other current assets $ 80.6 $ 93.8 Other long-term assets 1.4 4.0 Total $ 82.0 $ 97.8
Property and equipment	Property and equipment, net, consisted of the following (in millions): As of December 31, 2018 2017 Computers and equipment $ 1,100.0 $ 1,151.7 Software 223.3 217.8 Leasehold improvements 235.2 258.6 Furniture and fixtures 48.6 47.9 Building and building improvements 254.3 252.8 Land and land improvements 243.2 241.0 Construction-in-process 19.5 53.5 Property and equipment, gross 2,124.1 2,223.3 Accumulated depreciation (1,172.4 ) (1,202.2 ) Property and equipment, net $ 951.7 $ 1,021.1
Outstanding notes receivable and deposit	Total outstanding notes receivable and deposit, net of issuance costs, reported within other long-term assets in the Consolidated Balance Sheets were as follows (in millions): As of December 31, 2018 2017 Pulse Note (including accumulated interest paid in kind) $ 69.0 $ 61.2 Contract manufacturer deposit (non-interest bearing) 23.9 — Total $ 92.9 $ 61.2
Warranties	Changes in the Company’s warranty reserve were as follows (in millions): As of December 31, 2018 2017 Beginning balance $ 27.4 $ 41.3 Provisions made during the period, net 30.7 36.7 Actual costs incurred during the period (30.1 ) (50.6 ) Ending balance $ 28.0 $ 27.4
Deferred revenue	Details of the Company's deferred revenue, as reported in the Consolidated Balance Sheets, were as follows (in millions): As of December 31, 2018 2017 Deferred product revenue: Undelivered product commitments and other product deferrals $ 163.3 $ 312.6 Distributor inventory and other sell-through items — 68.1 Deferred gross product revenue 163.3 380.7 Deferred cost of product revenue (18.9 ) (46.5 ) Deferred product revenue, net 144.4 334.2 Deferred service revenue 1,069.2 1,205.1 Total $ 1,213.6 $ 1,539.3 Reported as: Current $ 829.3 $ 1,030.3 Long-term 384.3 509.0 Total $ 1,213.6 $ 1,539.3
Other (expense) income, net	Other expense, net consisted of the following (in millions): Years Ended December 31, 2018 2017 2016 Interest income $ 72.7 $ 53.0 $ 35.4 Interest expense (103.2 ) (101.2 ) (97.7 ) (Loss) gain on investments, net (7.4 ) 14.6 (1.8 ) Other (1.6 ) (2.7 ) 1.8 Other expense, net $ (39.5 ) $ (36.3 ) $ (62.3 )

Restructuring Charges (Tables)

Restructuring Charges (Tables)	12 Months Ended
	Dec. 31, 2018
Restructuring and Related Activities [Abstract]
Summary of restructuring charges	The following table presents restructuring charges included in the Consolidated Statements of Operations (in millions): Years Ended December 31, 2018 2017 2016 Severance $ 8.3 $ 57.7 $ 2.8 Facilities — — 0.5 Contract terminations (1.0 ) 7.9 — Total $ 7.3 $ 65.6 $ 3.3 Reported as: Restructuring charges $ 7.3 $ 65.6 $ 3.3 Total $ 7.3 $ 65.6 $ 3.3
Schedule of restructuring liabilities	The following table provides a summary of changes in the restructuring liabilities associated with the 2018 Restructuring Plan and prior year plans (in millions): December 31, Charges/ (Benefits) Cash December 31, Severance $ 17.7 $ 8.3 $ (25.0 ) $ 0.1 $ 1.1 Contract terminations and other 2.3 (1.0 ) (1.3 ) — — Total $ 20.0 $ 7.3 $ (26.3 ) $ 0.1 $ 1.1

Debt and Financing (Tables)

Debt and Financing (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Instruments [Abstract]
Long-term Debt	The following table summarizes the Company's total debt (in millions, except percentages): As of December 31, 2018 Issuance date Maturity Date Amount Effective Interest Rates Senior Notes ("Notes"): 3.125% fixed-rate notes ("2019 Notes") February 2016 February 2019 $ 350.0 3.36 % 3.300% fixed-rate notes ("2020 Notes") March 2015 June 2020 300.0 3.47 % 4.600% fixed-rate notes March 2011 March 2021 300.0 4.69 % 4.500% fixed-rate notes (*) ("2024 Notes") March 2014 March 2024 350.0 4.63 % 4.500% fixed-rate notes (*) ("2024 Notes") February 2016 March 2024 150.0 4.87 % 4.350% fixed-rate notes ("2025 Notes") March 2015 June 2025 300.0 4.47 % 5.950% fixed-rate notes March 2011 March 2041 400.0 6.03 % Total Notes 2,150.0 Unaccreted discount and debt issuance costs (11.0 ) Total $ 2,139.0 ________________________________ (*) 2024 Notes issued in March 2014 and February 2016 form a single series and are fully fungible.
Schedule of Maturities of Long-term Debt	As of December 31, 2018 , the Company's aggregate debt maturities based on outstanding principal were as follows (in millions): Years Ending December 31, Amount 2019 $ 350.0 2020 300.0 2021 300.0 2022 — 2023 — Thereafter 1,200.0 Total $ 2,150.0

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Repurchase and retirement of common stock and net issuances	The following table summarizes dividends paid, stock repurchases and retirements under the Company's stock repurchase programs, and stock repurchases for tax withholdings (in millions, except per share amounts): Dividends Stock Repurchases Total Year Per Share Amount Shares Average price Amount Tax Withholding Amount Amount 2018 (1) $ 0.72 $ 249.3 29.3 $ 25.62 $ 750.0 $ 6.6 $ 1,005.9 2017 (2) $ 0.40 $ 150.4 26.1 $ 27.61 $ 719.7 $ 6.1 $ 876.2 2016 (2) $ 0.40 $ 152.5 13.5 $ 23.25 $ 312.9 $ 11.7 $ 477.1 ________________________________ (1) Shares repurchased under the 2018 Stock Repurchase Program. $750.0 million represents the full amount of the ASR for which 23.3 million shares were received initially during the first quarter of 2018, and an additional 6.0 million shares were received at final settlement during the third quarter of 2018. (2) Shares repurchased under the 2014 Stock Repurchase Program.
Components of accumulated other comprehensive loss, net of taxes	The components of accumulated other comprehensive loss, net of related taxes, for the years ended December 31, 2018 , 2017 , and 2016 were as follows (in millions): Unrealized Gains/Losses on Available-for- Sale Debt Securities (1) Unrealized Gains/Losses on Cash Flow Hedges (2) Foreign Currency Translation Adjustments Total Balance as of December 31, 2015 $ 17.0 $ (1.3 ) $ (34.9 ) $ (19.2 ) Other comprehensive income (loss) before reclassifications 0.8 (2.1 ) (14.5 ) (15.8 ) Amount reclassified from accumulated other comprehensive loss (1.2 ) (1.1 ) — (2.3 ) Other comprehensive loss, net (0.4 ) (3.2 ) (14.5 ) (18.1 ) Balance as of December 31, 2016 $ 16.6 $ (4.5 ) $ (49.4 ) $ (37.3 ) Other comprehensive income before reclassifications 4.5 15.7 19.0 39.2 Amount reclassified from accumulated other comprehensive loss (2.1 ) (5.2 ) — (7.3 ) Other comprehensive income, net 2.4 10.5 19.0 31.9 Balance as of December 31, 2017 $ 19.0 $ 6.0 $ (30.4 ) $ (5.4 ) Other comprehensive income (loss) before reclassifications 0.6 (6.4 ) (12.4 ) (18.2 ) Amount reclassified from accumulated other comprehensive income (loss) 0.9 (1.2 ) — (0.3 ) Other comprehensive income (loss), net 1.5 (7.6 ) (12.4 ) (18.5 ) Reclassification of tax effects upon adoption of ASU 2018-02 5.0 0.7 — 5.7 Balance as of December 31, 2018 $ 25.5 $ (0.9 ) $ (42.8 ) $ (18.2 ) ________________________________ (1) The reclassifications out of accumulated other comprehensive loss during the years ended December 31, 2018 , 2017 , and 2016 for realized gains on available-for-sale debt securities were not material, and were included in other expense, net, in the Consolidated Statements of Operations. (2) The reclassifications out of accumulated other comprehensive loss during the years ended December 31, 2018 , 2017 , and 2016 for realized gains and losses 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 Consolidated Statements of Operations.

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Nonvested Share Activity	The following table summarizes the Company’s RSU, RSA, and PSA activity and related information as of and for the year ended December 31, 2018 (in millions, except per share amounts and years): Outstanding RSUs, RSAs, and PSAs (6) Number of Shares Weighted Average Grant-Date Fair Value per Share Weighted Average Remaining Contractual Term (In Years) Aggregate Intrinsic Value Balance at December 31, 2017 19.5 $ 25.39 RSUs granted (1)(2) 7.4 25.40 RSUs substituted in acquisitions (2)(5) 0.1 26.26 RSAs substituted in acquisitions (2)(5) 0.1 27.66 PSAs granted (2)(4) 0.9 24.62 RSUs vested (3) (6.5 ) 25.67 RSAs vested (3) (0.2 ) 25.12 PSAs vested (3) (1.1 ) 24.14 RSUs canceled (2.0 ) 25.92 PSAs canceled (0.8 ) 24.45 Balance at December 31, 2018 17.4 $ 25.32 1.0 $ 467.6 As of December 31, 2018 Vested and expected-to-vest RSUs, RSAs, and PSAs 15.5 $ 25.31 1.0 $ 418.4 ________________________________ (1) Includes service-based and market-based RSUs granted under the 2015 Plan according to their terms. (2) The weighted-average grant-date fair value of RSUs, RSAs, and PSAs granted and assumed or substituted during 2018 , 2017 , and 2016 was $25.33 , $27.53 , and $24.66 , respectively. (3) Total fair value of RSUs, RSAs, and PSAs vested during 2018 , 2017 , and 2016 was $200.5 million , $187.3 million , and $185.7 million , respectively. (4) 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 are achieved at target is 0.7 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 million to 1.0 million shares. (5) RSUs and RSAs substituted in connection with the acquisition of HTBase. (6) Excludes 1.9 million shares of PSAs that were modified in 2018, which relate primarily to PSAs assumed by the Company in connection with acquisitions consummated in 2016. These awards are contingent upon the achievement of certain performance milestones. The total incremental compensation cost resulting from the modifications totaled $6.9 million to be recognized over the remaining terms of the modified awards.
Shares available for grant	The following table presents the stock activity and the total number of shares available for grant under the 2015 Plan (in millions): Number of Shares Balance as of December 31, 2017 33.5 Additional shares authorized — RSUs and PSAs granted (1) (17.7 ) RSUs and PSAs canceled (2) 5.4 Options canceled/expired (2) 0.7 Balance as of December 31, 2018 21.9 ________________________________ (1) RSUs and PSAs with a per share or unit purchase price lower than 100% of the fair market value of the Company's common stock on the day of the grant under the 2015 Plan are counted against shares authorized under the plan as two and one-tenth shares of common stock for each share subject to such award. The number of shares subject to PSAs granted represents the maximum number of shares that may be issued pursuant to the award over its full term. (2) Canceled or expired options and canceled RSUs and PSAs under the 2006 Plan are no longer available for future grant under such plan; however, the number of shares available for grant under the 2015 Plan are increased by (i) the amount of such canceled or expired options and (ii) two and one-tenth the shares for each canceled RSUs or PSAs, as applicable, up to a maximum of 29.0 million additional shares of common stock, pursuant to the terms of the 2015 Plan.
Schedule Of Share-based Payment Award, Stock Options and Employee Stock Purchase Plan, Valuation Assumptions	The weighted-average assumptions used and the resulting estimates of fair value for ESPP and market-based RSUs were as follows: Years Ended December 31, 2018 2017 2016 ESPP: Volatility 29% 25% 32% Risk-free interest rate 1.9% 0.9% 0.4% Expected life (years) 1.2 0.5 0.5 Dividend yield 2.7% 1.5% 1.8% Weighted-average fair value per share $6.93 $6.04 $5.56 Market-based RSUs: Volatility 28% 30% 36% Risk-free interest rate 2.4% 1.9% 1.2% Dividend yield 2.6% 1.4% 1.7% Weighted-average fair value per share $28.39 $19.30 $14.71
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 Company's Consolidated Statements of Operations (in millions): Years Ended December 31, 2018 2017 2016 Cost of revenues - Product $ 6.3 $ 4.6 $ 6.4 Cost of revenues - Service 18.0 17.5 15.3 Research and development 120.6 86.6 126.5 Sales and marketing 51.1 55.6 55.2 General and administrative 21.1 23.2 23.4 Total $ 217.1 $ 187.5 $ 226.8
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award	The following table summarizes share-based compensation expense by award type (in millions): Years Ended December 31, 2018 2017 2016 Stock options $ 0.4 $ 0.5 $ 4.4 RSUs, RSAs, and PSAs 198.2 171.3 206.9 ESPP 18.5 15.7 15.5 Total $ 217.1 $ 187.5 $ 226.8

Segments (Tables)

Segments (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Financial information for each segment	The following table presents net revenues by product and service (in millions): Years Ended December 31, 2018 2017 2016 Routing $ 1,839.7 $ 2,189.5 $ 2,352.9 Switching 934.4 963.4 858.0 Security 333.0 293.3 318.0 Total product 3,107.1 3,446.2 3,528.9 Total service 1,540.4 1,581.0 1,461.2 Total $ 4,647.5 $ 5,027.2 $ 4,990.1 The following table presents net revenues by customer vertical (*) (in millions): Years Ended December 31, 2018 2017 2016 Cloud $ 1,049.9 $ 1,310.7 $ 1,315.9 Service Provider 2,066.7 2,319.4 2,316.4 Enterprise 1,530.9 1,397.1 1,357.8 Total $ 4,647.5 $ 5,027.2 $ 4,990.1 ________________________________ (*) Certain prior-period amounts have been reclassified to conform to the current-period classifications.
Disaggregation of revenue	The following table presents net revenues by product and service (in millions): Years Ended December 31, 2018 2017 2016 Routing $ 1,839.7 $ 2,189.5 $ 2,352.9 Switching 934.4 963.4 858.0 Security 333.0 293.3 318.0 Total product 3,107.1 3,446.2 3,528.9 Total service 1,540.4 1,581.0 1,461.2 Total $ 4,647.5 $ 5,027.2 $ 4,990.1 The following table presents net revenues by customer vertical (*) (in millions): Years Ended December 31, 2018 2017 2016 Cloud $ 1,049.9 $ 1,310.7 $ 1,315.9 Service Provider 2,066.7 2,319.4 2,316.4 Enterprise 1,530.9 1,397.1 1,357.8 Total $ 4,647.5 $ 5,027.2 $ 4,990.1 ________________________________ (*) Certain prior-period amounts have been reclassified to conform to the current-period classifications. 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): Years Ended December 31, 2018 2017 2016 Americas: United States $ 2,339.1 $ 2,712.6 $ 2,737.0 Other 202.1 234.6 231.8 Total Americas 2,541.2 2,947.2 2,968.8 Europe, Middle East, and Africa 1,290.8 1,195.8 1,238.1 Asia Pacific 815.5 884.2 783.2 Total $ 4,647.5 $ 5,027.2 $ 4,990.1
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): Years Ended December 31, 2018 2017 2016 Americas: United States $ 2,339.1 $ 2,712.6 $ 2,737.0 Other 202.1 234.6 231.8 Total Americas 2,541.2 2,947.2 2,968.8 Europe, Middle East, and Africa 1,290.8 1,195.8 1,238.1 Asia Pacific 815.5 884.2 783.2 Total $ 4,647.5 $ 5,027.2 $ 4,990.1
Property and equipment, net by geographic region	The following table presents geographic information for property and equipment, net and purchased intangible assets, net (in millions): As of December 31, 2018 2017 United States $ 941.7 $ 1,005.1 International 128.5 144.1 Property and equipment, net and purchased intangible assets, net $ 1,070.2 $ 1,149.2

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Components of income before the provision for income taxes and noncontrolling interest	The components of pretax income are summarized as follows (in millions): Years Ended December 31, 2018 2017 2016 Domestic $ 160.6 $ 474.2 $ 466.2 Foreign 372.1 337.6 361.2 Total pretax income $ 532.7 $ 811.8 $ 827.4
Schedule of Components of Provision for Income Taxes	The (benefit) provision for income taxes is summarized as follows (in millions): Years Ended December 31, 2018 2017 2016 Current (benefit) provision: Federal $ (126.1 ) $ 594.3 $ 121.4 States 9.0 13.9 10.3 Foreign 38.9 45.4 46.0 Total current (benefit) provision (78.2 ) 653.6 177.7 Deferred (benefit) provision: Federal 36.6 (128.7 ) 57.2 States 2.2 (17.7 ) 4.3 Foreign 5.2 (1.6 ) (4.5 ) Total deferred (benefit) provision 44.0 (148.0 ) 57.0 Total (benefit) provision for income taxes $ (34.2 ) $ 505.6 $ 234.7
Schedule of Effective Income Tax Rate Reconciliation	The (benefit) provision for income taxes differs from the amount computed by applying the federal statutory rate of 21% for 2018 and 35% for 2017 and 2016, respectively, to pretax income as follows (in millions): Years Ended December 31, 2018 2017 2016 Expected provision at statutory rate $ 111.9 $ 284.1 $ 289.6 State taxes, net of federal benefit 7.4 12.0 8.9 Foreign income at different tax rates (12.8 ) (46.4 ) (53.4 ) R&D tax credits (22.1 ) (15.1 ) (16.8 ) Share-based compensation 4.7 — 10.5 Release of valuation allowance — (1.7 ) (0.7 ) Domestic production activities — (12.4 ) (9.5 ) Non-deductible compensation 1.9 1.6 2.4 Impact of the U.S. Tax Cuts and Jobs Act 2.8 289.5 — Tax accounting method changes (65.4 ) — — Lapses in federal statutes of limitations (67.6 ) — — Other 5.0 (6.0 ) 3.7 Total (benefit) provision for income taxes $ (34.2 ) $ 505.6 $ 234.7
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company's long-term deferred tax assets and deferred tax liabilities are as follows (in millions): As of December 31, 2018 2017 Deferred tax assets: Net operating loss carry-forwards $ 12.9 $ 18.3 Research and other credit carry-forwards 220.0 198.8 Deferred revenue 37.7 103.5 Share-based compensation 26.1 31.1 Cost sharing adjustment 12.2 12.4 Reserves and accruals not currently deductible 62.7 76.7 Other 13.2 12.8 Total deferred tax assets 384.8 453.6 Valuation allowance (233.7 ) (214.5 ) Deferred tax assets, net of valuation allowance 151.1 239.1 Deferred tax liabilities: Property and equipment basis differences (40.6 ) (42.5 ) Purchased intangibles (13.7 ) (12.4 ) Unremitted foreign earnings (26.4 ) (25.4 ) Deferred compensation and other (8.9 ) (10.4 ) Total deferred tax liabilities (89.6 ) (90.7 ) Net deferred tax assets $ 61.5 $ 148.4
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of the Company's total gross unrecognized tax benefits was as follows (in millions): Years Ended December 31, 2018 2017 2016 Balance at beginning of year $ 264.5 $ 223.1 $ 216.1 Tax positions related to current year: Additions 4.3 64.6 27.2 Tax positions related to prior years: Additions 12.7 1.8 1.0 Reductions (33.8 ) (16.6 ) (4.1 ) Settlements (2.6 ) (4.0 ) (14.3 ) Lapses in statutes of limitations (67.0 ) (4.4 ) (2.8 ) Balance at end of year $ 178.1 $ 264.5 $ 223.1

Net Income per Share (Tables)

Net Income per Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Schedule of Calculation of Basic and Diluted Net Income Per Share	The Company computed basic and diluted net income per share as follows (in millions, except per share amounts): Years Ended December 31, 2018 2017 2016 Numerator: Net income $ 566.9 $ 306.2 $ 592.7 Denominator: Weighted-average shares used to compute basic net income per share 349.0 377.7 381.7 Dilutive effect of employee stock awards 5.4 6.5 6.1 Weighted-average shares used to compute diluted net income per share 354.4 384.2 387.8 Net income per share: Basic $ 1.62 $ 0.81 $ 1.55 Diluted $ 1.60 $ 0.80 $ 1.53 Anti-dilutive shares 3.9 1.1 2.5

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	The following table summarizes the Company’s unconditional purchase obligations and future minimum payments under non-cancelable operating and other lease arrangements for each of the next five years and thereafter as of December 31, 2018 (in millions): Leases Years Ending December 31, Unconditional Purchase Obligations Operating Leases Other Lease Arrangement 2019 $ 43.1 $ 33.7 $ 13.1 2020 26.4 30.7 13.3 2021 11.4 24.3 13.6 2022 8.5 17.0 13.9 2023 5.5 14.3 14.2 Thereafter 2.9 26.3 32.9 Total $ 97.8 $ 146.3 $ 101.0
Schedule of Other Lease Arrangement	The following table summarizes the Company’s unconditional purchase obligations and future minimum payments under non-cancelable operating and other lease arrangements for each of the next five years and thereafter as of December 31, 2018 (in millions): Leases Years Ending December 31, Unconditional Purchase Obligations Operating Leases Other Lease Arrangement 2019 $ 43.1 $ 33.7 $ 13.1 2020 26.4 30.7 13.3 2021 11.4 24.3 13.6 2022 8.5 17.0 13.9 2023 5.5 14.3 14.2 Thereafter 2.9 26.3 32.9 Total $ 97.8 $ 146.3 $ 101.0
Unrecorded Unconditional Purchase Obligations Disclosure	The following table summarizes the Company’s unconditional purchase obligations and future minimum payments under non-cancelable operating and other lease arrangements for each of the next five years and thereafter as of December 31, 2018 (in millions): Leases Years Ending December 31, Unconditional Purchase Obligations Operating Leases Other Lease Arrangement 2019 $ 43.1 $ 33.7 $ 13.1 2020 26.4 30.7 13.3 2021 11.4 24.3 13.6 2022 8.5 17.0 13.9 2023 5.5 14.3 14.2 Thereafter 2.9 26.3 32.9 Total $ 97.8 $ 146.3 $ 101.0

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Schedule of Selected Quarterly Financial Data (Unaudited)	The table below sets forth selected unaudited financial data for each quarter of the years ended December 31, 2018 and December 31, 2017 (in millions, except per share amounts): Year Ended December 31, 2018 Year Ended December 31, 2017 First Quarter Second Quarter Third Quarter Fourth Quarter First Quarter Second Quarter Third Quarter Fourth Quarter Net revenues $ 1,082.6 $ 1,204.1 $ 1,179.8 $ 1,181.0 $ 1,221.0 $ 1,308.9 $ 1,257.8 $ 1,239.5 Gross margin 618.4 700.9 711.0 710.9 746.6 801.9 772.4 751.2 Income before income taxes 41.4 150.9 152.0 188.4 140.6 245.2 225.8 200.2 Net income (loss) (1) $ 34.4 $ 116.5 $ 223.8 $ 192.2 $ 108.8 $ 179.8 $ 165.7 $ (148.1 ) Net income (loss) per share: (2) Basic $ 0.10 $ 0.33 $ 0.65 $ 0.56 $ 0.29 $ 0.47 $ 0.44 $ (0.40 ) Diluted (3) $ 0.10 $ 0.33 $ 0.64 $ 0.55 $ 0.28 $ 0.47 $ 0.43 $ (0.40 ) _______________ (1) Net income for the third and fourth quarters of 2018 include a lower statutory tax rate due to the Tax Act and tax benefits related to items unique to 2018. See Note 14, Income Taxes , for further discussion. Net loss for the fourth quarter of 2017 includes an estimated $289.5 million of tax expense related to the Tax Act, and restructuring charges of $36.2 million . (2) Net income (loss) per share is computed independently. Therefore, the sum of the quarterly net income per share may not equal the total computed for the year or any cumulative interim period. (3) Potentially dilutive common shares for the fourth quarter of 2017 were excluded from the computation of diluted net loss per share because their effect would be anti-dilutive.

Description of Business and B_2

Description of Business and Basis of Presentation - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Restricted cash	$ 52.6	$ 47.4	$ 0.4

Significant Accounting Polici_4

Significant Accounting Policies - Narrative (Details) $ in Millions	Jan. 01, 2018USD ($)	Dec. 31, 2018USD ($)Customer	Dec. 31, 2017USD ($)Customer	Dec. 31, 2016USD ($)Customer	Jan. 01, 2019USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Maturity of highly liquid investments		3 months
Warranty period for hardware products (in years)		1 year
Warranty period for software (in days)		90 days
Advertising expense		$ 20	$ 19.9	$ 15.8
More than likely percentage of being realized upon settlement, tax benefit		50.00%
Liability for unrecognized tax benefits as current, period		1 year
Number of customers accounting for more than 10% of revenues | Customer		0	0	0
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of tax effects upon adoption of ASU 2018-02		$ (5.7)
Accounting Standards Update 2018-02 | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of tax effects upon adoption of ASU 2018-02	$ (5.7)
Accounting Standards Update 2014-09 | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect on retained earnings, net of tax	324.7
Cumulative effect on retained earnings, tax	$ 63.9
Accounting Standards Update 2016-02 | Forecast | Subsequent Event
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
ROU assets					$ 200
Lease liability					$ 230
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customers, terms of payment (in days)		30 days
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contract with customers, terms of payment (in days)		90 days
Computers, equipment, and software | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		1 year 6 months
Computers, equipment, and software | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		7 years
Furniture and fixtures | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		5 years
Furniture and fixtures | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		7 years
Building and building improvements | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		7 years
Building and building improvements | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		40 years
Land improvements | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		10 years
Land improvements | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		40 years
Leasehold improvements
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life		10 years

Significant Accounting Polici_5

Significant Accounting Policies - Contract Revenue Adjustments on Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net of allowance for doubtful accounts of $4.9 and $5.7 as of December 31, 2018 and 2017, respectively	$ 754.6	$ 850.1	$ 852
Prepaid expenses and other current assets	268.1	331.4	299.9
Other long-term assets	403.5	394.4	415.5
Total assets	9,363.3	9,842.3	9,833.8
Deferred revenue	829.3	804.9	1,030.3
Other accrued liabilities	233.5	338.1	304.3
Long-term deferred revenue	384.3	384.4	509
Total liabilities	4,540.1	4,836.7	5,152.9
Accumulated deficit	(2,831.4)	(3,031.1)	(3,355.8)
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net of allowance for doubtful accounts of $4.9 and $5.7 as of December 31, 2018 and 2017, respectively	746.3		852
Prepaid expenses and other current assets	241.6		299.9
Other long-term assets	400.4		415.5
Total assets	9,325.6		9,833.8
Deferred revenue	1,111.9		1,030.3
Other accrued liabilities	178.6		304.3
Long-term deferred revenue	431.8		509
Total liabilities	4,815.2		5,152.9
Accumulated deficit	(3,144.3)		$ (3,355.8)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net of allowance for doubtful accounts of $4.9 and $5.7 as of December 31, 2018 and 2017, respectively	8.3	(1.9)
Prepaid expenses and other current assets	26.5	31.5
Other long-term assets	3.1	(21.1)
Total assets	37.7	8.5
Deferred revenue	(282.6)	(225.4)
Other accrued liabilities	54.9	33.8
Long-term deferred revenue	(47.5)	(124.6)
Total liabilities	(275.1)	(316.2)
Accumulated deficit	$ 312.9	$ 324.7

Significant Accounting Polici_6

Significant Accounting Policies - Contract Revenue Adjustments on Income Statement (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 1,181	$ 1,179.8	$ 1,204.1	$ 1,082.6	$ 1,239.5	$ 1,257.8	$ 1,308.9	$ 1,221	$ 4,647.5	$ 5,027.2	$ 4,990.1
Sales and marketing									927.4	950.2	972.9
Product
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									3,107.1	3,446.2	3,528.9
Service
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									1,540.4	$ 1,581	$ 1,461.2
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									4,670.1
Sales and marketing									929.3
Calculated under Revenue Guidance in Effect before Topic 606 | Product
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									3,006.8
Calculated under Revenue Guidance in Effect before Topic 606 | Service
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									1,663.3
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									(22.6)
Sales and marketing									(1.9)
Difference between Revenue Guidance in Effect before and after Topic 606 | Product | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									100.3
Difference between Revenue Guidance in Effect before and after Topic 606 | Service | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues									$ (122.9)

Business Combinations - Purchas

Business Combinations - Purchase Price Allocation (Details) - USD ($) $ in Millions	Dec. 07, 2018	Sep. 18, 2017	Dec. 06, 2016	Aug. 09, 2016	Apr. 01, 2016
HTBase
Business Acquisition [Line Items]
Net tangible assets acquired/(liabilities) assumed	$ (1)
Intangible assets	7.8
Goodwill	14.4
Total	$ 21.2
Cyphort
Business Acquisition [Line Items]
Net tangible assets acquired/(liabilities) assumed		$ 1.4
Intangible assets		15.4
Goodwill		16.7
Total		$ 33.5
AppFormix
Business Acquisition [Line Items]
Net tangible assets acquired/(liabilities) assumed			$ (5.3)
Intangible assets			20.3
Goodwill			32.9
Total			$ 47.9
Aurrion
Business Acquisition [Line Items]
Net tangible assets acquired/(liabilities) assumed				$ 6
Intangible assets				49
Goodwill				46.9
Total				$ 101.9
BTI
Business Acquisition [Line Items]
Net tangible assets acquired/(liabilities) assumed					$ (19.7)
Intangible assets					43.3
Goodwill					20.2
Total					$ 43.8

Business Combinations - Intangi

Business Combinations - Intangible Assets Acquired (Details) - USD ($) $ in Millions	Dec. 07, 2018	Sep. 18, 2017	Dec. 06, 2016	Apr. 01, 2016	Aug. 09, 2016
Cyphort
Business Acquisition [Line Items]
Finite-lived intangible assets:		$ 15.4
Intangible assets		15.4
Cyphort | IPR&D
Business Acquisition [Line Items]
Indefinite-lived intangible assets:		$ 0
Cyphort | Existing technology
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)		5 years
Finite-lived intangible assets:		$ 15.4
Cyphort | Customer relationships
Business Acquisition [Line Items]
Finite-lived intangible assets:		0
Cyphort | Other
Business Acquisition [Line Items]
Finite-lived intangible assets:		$ 0
AppFormix
Business Acquisition [Line Items]
Finite-lived intangible assets:			$ 20.3
Intangible assets			20.3
AppFormix | IPR&D
Business Acquisition [Line Items]
Indefinite-lived intangible assets:			$ 0
AppFormix | Existing technology
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)			5 years
Finite-lived intangible assets:			$ 20.1
AppFormix | Customer relationships
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)			1 year
Finite-lived intangible assets:			$ 0.2
AppFormix | Other
Business Acquisition [Line Items]
Finite-lived intangible assets:			$ 0
Aurrion
Business Acquisition [Line Items]
Finite-lived intangible assets:					$ 0
Intangible assets					49
Aurrion | IPR&D
Business Acquisition [Line Items]
Intangible assets					49
Aurrion | Existing technology
Business Acquisition [Line Items]
Finite-lived intangible assets:					0
Aurrion | Customer relationships
Business Acquisition [Line Items]
Finite-lived intangible assets:					0
Aurrion | Other
Business Acquisition [Line Items]
Finite-lived intangible assets:					$ 0
BTI
Business Acquisition [Line Items]
Finite-lived intangible assets:				$ 43.3
Intangible assets				43.3
BTI | IPR&D
Business Acquisition [Line Items]
Indefinite-lived intangible assets:				$ 0
BTI | Existing technology
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)				8 years
Finite-lived intangible assets:				$ 37.1
BTI | Customer relationships
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)				8 years
Finite-lived intangible assets:				$ 5.3
BTI | Other
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)				1 year
Finite-lived intangible assets:				$ 0.9
HTBase
Business Acquisition [Line Items]
Finite-lived intangible assets:	$ 7.8
Intangible assets	7.8
HTBase | IPR&D
Business Acquisition [Line Items]
Indefinite-lived intangible assets:	$ 0
HTBase | Existing technology
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)	4 years
Finite-lived intangible assets:	$ 7.8
HTBase | Customer relationships
Business Acquisition [Line Items]
Finite-lived intangible assets:	0
HTBase | Other
Business Acquisition [Line Items]
Finite-lived intangible assets:	$ 0

Business Combinations - Narrati

Business Combinations - Narrative (Details) - USD ($) $ in Millions	Dec. 07, 2018	Sep. 18, 2017	Dec. 06, 2016	Aug. 09, 2016	Apr. 01, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Aug. 08, 2016	Mar. 31, 2016
Business Acquisition [Line Items]
Acquisition related costs						$ 4.4	$ 2.1	$ 11.8
HTBase
Business Acquisition [Line Items]
Payments to acquire business	$ 19.6
Fair value of pre-existing debt	1.6
Share-based awards assumed, fair value	$ 3.8
Voting interest acquired	100.00%
Cyphort
Business Acquisition [Line Items]
Payments to acquire business		$ 33.5
Share-based awards assumed, fair value		$ 3.8
Voting interest acquired		100.00%
AppFormix
Business Acquisition [Line Items]
Payments to acquire business			$ 47.9
Share-based awards assumed, fair value			$ 23.9
Voting interest acquired			100.00%
Aurrion
Business Acquisition [Line Items]
Payments to acquire business				$ 74.3
Share-based awards assumed, fair value				$ 55
Ownership interest prior to acquisition of remaining ownership interest									18.00%
Ownership interest				100.00%
Fair value of pre-existing equity investment				$ 17.2
Fair value of pre-existing convertible debt				$ 10.4
BTI
Business Acquisition [Line Items]
Payments to acquire business					$ 25.8
Fair value of pre-existing debt					0.9
Share-based awards assumed, fair value					$ 8.6
Ownership interest prior to acquisition of remaining ownership interest										12.00%
Ownership interest					100.00%
Fair value of pre-existing equity investment					$ 17.1
Repayment of liabilities assumed					$ 18.6

Cash Equivalents and Investme_3

Cash Equivalents and Investments - Available for Sale Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale debt securities:
Amortized Cost	$ 2,223.6	$ 2,386.3
Gross Unrealized Gains	37.4	37.9
Gross Unrealized Losses	4.2	5.4
Estimated Fair Value	2,256.8	2,418.8
Cash equivalents
Available-for-sale debt securities:
Amortized Cost	936.5	351
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	936.5	351
Short-term investments
Available-for-sale debt securities:
Amortized Cost	1,069.2	1,027.2
Gross Unrealized Gains	0	0.1
Gross Unrealized Losses	1.9	1.2
Estimated Fair Value	1,067.3	1,026.1
Long-term investments
Available-for-sale debt securities:
Amortized Cost	201.3	992.2
Gross Unrealized Gains	0	0.4
Gross Unrealized Losses	2.3	4.2
Estimated Fair Value	199	988.4
Other long-term assets
Available-for-sale debt securities:
Amortized Cost	16.6	15.9
Gross Unrealized Gains	37.4	37.4
Gross Unrealized Losses	0	0
Estimated Fair Value	54	53.3
Asset-backed securities
Available-for-sale debt securities:
Amortized Cost	46.8	287.1
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0.3	0.6
Estimated Fair Value	46.5	286.5
Certificates of deposit
Available-for-sale debt securities:
Amortized Cost	152.9	83.8
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	152.9	83.8
Commercial paper
Available-for-sale debt securities:
Amortized Cost	393.6	217.1
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	393.6	217.1
Corporate debt securities
Available-for-sale debt securities:
Amortized Cost	416.1	929.6
Gross Unrealized Gains	0	0.4
Gross Unrealized Losses	3.1	3
Estimated Fair Value	413	927
Foreign government debt securities
Available-for-sale debt securities:
Amortized Cost	20	62.9
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0.1	0.2
Estimated Fair Value	19.9	62.7
Time deposits
Available-for-sale debt securities:
Amortized Cost	278.6	239.2
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	278.6	239.2
U.S. government agency securities
Available-for-sale debt securities:
Amortized Cost	87.2	143.9
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0.2	0.7
Estimated Fair Value	87	143.2
U.S. government securities
Available-for-sale debt securities:
Amortized Cost	811.8	406.8
Gross Unrealized Gains	0	0.1
Gross Unrealized Losses	0.5	0.9
Estimated Fair Value	811.3	406
Fixed income securities
Available-for-sale debt securities:
Amortized Cost	2,207	2,370.4
Gross Unrealized Gains	0	0.5
Gross Unrealized Losses	4.2	5.4
Estimated Fair Value	2,202.8	2,365.5
Privately-held debt and redeemable preferred stock securities
Available-for-sale debt securities:
Amortized Cost	16.6	15.9
Gross Unrealized Gains	37.4	37.4
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 54	$ 53.3

Cash Equivalents and Investme_4

Cash Equivalents and Investments - Maturities of Available for Sale Investments (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Amortized Cost
Amortized Cost	$ 2,223.6	$ 2,386.3
Estimated Fair Value
Total	2,256.8	2,418.8
Fixed Income Securities
Amortized Cost
Due in less than one year	2,005.7
Due between one and five years	201.3
Amortized Cost	2,207	2,370.4
Estimated Fair Value
Due in less than one year	2,003.8
Due between one and five years	199
Total	$ 2,202.8	$ 2,365.5

Cash Equivalents and Investme_5

Cash Equivalents and Investments - Unrealized Loss Position on Fixed Income Securities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value
Less than 12 Months	$ 423.2	$ 1,238.3
12 Months or Greater	500.8	273.3
Total	924	1,511.6
Unrealized Loss
Less than 12 Months	0.1	3.6
12 Months or Greater	4.1	1.8
Total	4.2	5.4
Asset-backed securities
Fair Value
Less than 12 Months	3.1	215.2
12 Months or Greater	43	38.4
Total	46.1	253.6
Unrealized Loss
Less than 12 Months	0	0.4
12 Months or Greater	0.3	0.2
Total	0.3	0.6
Corporate debt securities
Fair Value
Less than 12 Months	72.6	646.7
12 Months or Greater	330.7	108.6
Total	403.3	755.3
Unrealized Loss
Less than 12 Months	0.1	2.1
12 Months or Greater	3	0.9
Total	3.1	3
Foreign government debt securities
Fair Value
Less than 12 Months	1.5	47.3
12 Months or Greater	18.4	6.6
Total	19.9	53.9
Unrealized Loss
Less than 12 Months	0	0.2
12 Months or Greater	0.1	0
Total	0.1	0.2
U.S. government agency securities
Fair Value
Less than 12 Months	2	68.3
12 Months or Greater	45.2	67.9
Total	47.2	136.2
Unrealized Loss
Less than 12 Months	0	0.2
12 Months or Greater	0.2	0.5
Total	0.2	0.7
U.S. government securities
Fair Value
Less than 12 Months	344	260.8
12 Months or Greater	63.5	51.8
Total	407.5	312.6
Unrealized Loss
Less than 12 Months	0	0.7
12 Months or Greater	0.5	0.2
Total	$ 0.5	$ 0.9

Cash Equivalents and Investme_6

Cash Equivalents and Investments - Narrative (Details)	12 Months Ended
	Dec. 31, 2018USD ($)Investment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Total investments In unrealized loss position | Investment	490
OTTI, associated with credit losses	$ 0
Available-for-sale debt securities, gross realized gain	0	$ 0	$ 0
Available-for-sale debt securities, gross realized losses	0	0	0
Equity investments, unrealized gains (losses)	(3,200,000)
Equity investments, unrealized gains		0	0
Equity investments, unrealized losses		0	0
Restricted cash and investments	52,700,000
Prepaid expenses and other current assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	27,600,000
Other long-term assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	25,100,000
Debt Securities
Restricted Cash and Cash Equivalents Items [Line Items]
OTTI, associated with credit losses	$ 0	$ 0	$ 0

Cash Equivalents and Investme_7

Cash Equivalents and Investments - Equity Securities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity investments without readily determinable fair value	$ 36.4
Total equity securities	1,060.4
Equity investments without readily determinable fair value		$ 29.7
Total equity securities		1,027.1
Cash equivalents
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Total equity securities	985.3
Total equity securities		928
Short-term investments
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Total equity securities	2.8
Total equity securities		0
Prepaid expenses and other current assets
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Total equity securities	10.9
Total equity securities		36.3
Other long-term assets
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Total equity securities	61.4
Total equity securities		62.8
Money market funds
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity investments with readily determinable fair value	996.9
Equity investments with readily determinable fair value		969.8
Mutual funds
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity investments with readily determinable fair value	24.3
Equity investments with readily determinable fair value		27.6
Publicly-traded equity securities
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity investments with readily determinable fair value	$ 2.8
Equity investments with readily determinable fair value		$ 0

Cash Equivalents and Investme_8

Cash Equivalents and Investments Cash Equivalents and Investments - Restricted Cash and Investments (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 2,489	$ 2,006.5
Restricted cash		52.6	$ 47.4	$ 0.4
Total cash, cash equivalents, and restricted cash	2,505.8	2,059.1	$ 1,880.6	$ 1,421.3
Prepaid expenses and other current assets
Cash and Cash Equivalents [Line Items]
Restricted cash	16.8	49.6
Other long-term assets
Cash and Cash Equivalents [Line Items]
Restricted cash	$ 0	$ 3

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	$ 2,256.8	$ 2,418.8
Derivative liabilities:
Acquisition-related escrows	11.6	16.8
Indemnification trust		25
Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	936.5	351
Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	1,067.3	1,026.1
Long-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	199	988.4
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	46.5	286.5
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	152.9	83.8
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	393.6	217.1
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	413	927
Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	19.9	62.7
Time deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	278.6	239.2
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	87	143.2
U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	811.3	406
Privately-held debt and redeemable preferred stock securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	54	53.3
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	996.9
Equity investments with readily determinable fair value		969.8
Publicly-traded equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2.8
Equity investments with readily determinable fair value		0
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	1,024
Equity investments with readily determinable fair value		997.4
Derivative assets:
Assets, Fair Value Disclosure	3,286.1	3,425.4
Derivative liabilities:
Liability measured at non-recurring basis	7.1	1.8
Fair Value, Measurements, Recurring | Cash equivalents
Derivative assets:
Assets, Fair Value Disclosure	1,921.8	1,279
Fair Value, Measurements, Recurring | Short-term investments
Derivative assets:
Assets, Fair Value Disclosure	1,070.1	1,026.1
Fair Value, Measurements, Recurring | Long-term investments
Derivative assets:
Assets, Fair Value Disclosure	199	988.4
Fair Value, Measurements, Recurring | Prepaid expenses and other current assets
Derivative assets:
Assets, Fair Value Disclosure	16.1	45.5
Fair Value, Measurements, Recurring | Other long-term assets
Derivative assets:
Assets, Fair Value Disclosure	79.1	86.4
Fair Value, Measurements, Recurring | Other accrued liabilities
Derivative liabilities:
Liability measured at non-recurring basis	7.1	1.8
Fair Value, Measurements, Recurring | Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	5.3	9.2
Derivative liabilities:
Foreign exchange contracts	(7.1)	(1.8)
Fair Value, Measurements, Recurring | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	2,256.8	2,418.8
Fair Value, Measurements, Recurring | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	46.5	286.5
Fair Value, Measurements, Recurring | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	152.9	83.8
Fair Value, Measurements, Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	393.6	217.1
Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	413	927
Fair Value, Measurements, Recurring | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	19.9	62.7
Fair Value, Measurements, Recurring | Time deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	278.6	239.2
Fair Value, Measurements, Recurring | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	87	143.2
Fair Value, Measurements, Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	811.3	406
Fair Value, Measurements, Recurring | Privately-held debt and redeemable preferred stock securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	54	53.3
Fair Value, Measurements, Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	996.9
Equity investments with readily determinable fair value		969.8
Fair Value, Measurements, Recurring | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	24.3
Equity investments with readily determinable fair value		27.6
Fair Value, Measurements, Recurring | Publicly-traded equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2.8
Equity investments with readily determinable fair value		0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	1,024
Equity investments with readily determinable fair value		997.4
Derivative assets:
Assets, Fair Value Disclosure	1,376.8	1,319.8
Derivative liabilities:
Liability measured at non-recurring basis	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Cash equivalents
Derivative assets:
Assets, Fair Value Disclosure	1,025.2	928.1
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Short-term investments
Derivative assets:
Assets, Fair Value Disclosure	297.5	247.5
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Long-term investments
Derivative assets:
Assets, Fair Value Disclosure	18.2	74.8
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Prepaid expenses and other current assets
Derivative assets:
Assets, Fair Value Disclosure	10.8	36.3
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Other long-term assets
Derivative assets:
Assets, Fair Value Disclosure	25.1	33.1
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Other accrued liabilities
Derivative liabilities:
Liability measured at non-recurring basis	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	0	0
Derivative liabilities:
Foreign exchange contracts	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	352.8	322.4
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Time deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	352.8	322.4
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Privately-held debt and redeemable preferred stock securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	996.9
Equity investments with readily determinable fair value		969.8
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	24.3
Equity investments with readily determinable fair value		27.6
Quoted Prices in Active Markets For Identical Assets (Level 1) | Fair Value, Measurements, Recurring | Publicly-traded equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2.8
Equity investments with readily determinable fair value		0
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Equity investments with readily determinable fair value		0
Derivative assets:
Assets, Fair Value Disclosure	1,855.3	2,052.3
Derivative liabilities:
Liability measured at non-recurring basis	7.1	1.8
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Cash equivalents
Derivative assets:
Assets, Fair Value Disclosure	896.6	350.9
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Short-term investments
Derivative assets:
Assets, Fair Value Disclosure	772.6	778.6
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Long-term investments
Derivative assets:
Assets, Fair Value Disclosure	180.8	913.6
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Prepaid expenses and other current assets
Derivative assets:
Assets, Fair Value Disclosure	5.3	9.2
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Other long-term assets
Derivative assets:
Assets, Fair Value Disclosure	0	0
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Other accrued liabilities
Derivative liabilities:
Liability measured at non-recurring basis	7.1	1.8
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	5.3	9.2
Derivative liabilities:
Foreign exchange contracts	(7.1)	(1.8)
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	1,850	2,043.1
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	46.5	286.5
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	152.9	83.8
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	393.6	217.1
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	413	927
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	19.9	62.7
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Time deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	278.6	239.2
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	87	143.2
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	458.5	83.6
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Privately-held debt and redeemable preferred stock securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Equity investments with readily determinable fair value		0
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Equity investments with readily determinable fair value		0
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring | Publicly-traded equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Equity investments with readily determinable fair value		0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Equity investments with readily determinable fair value		0
Derivative assets:
Assets, Fair Value Disclosure	54	53.3
Derivative liabilities:
Liability measured at non-recurring basis	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Cash equivalents
Derivative assets:
Assets, Fair Value Disclosure	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Short-term investments
Derivative assets:
Assets, Fair Value Disclosure	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Long-term investments
Derivative assets:
Assets, Fair Value Disclosure	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Prepaid expenses and other current assets
Derivative assets:
Assets, Fair Value Disclosure	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Other long-term assets
Derivative assets:
Assets, Fair Value Disclosure	54	53.3
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Other accrued liabilities
Derivative liabilities:
Liability measured at non-recurring basis	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	0	0
Derivative liabilities:
Foreign exchange contracts	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	54	53.3
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Foreign government debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Time deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Privately-held debt and redeemable preferred stock securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale debt securities	54	53.3
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Equity investments with readily determinable fair value		0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0
Equity investments with readily determinable fair value		0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring | Publicly-traded equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	$ 0
Equity investments with readily determinable fair value		$ 0

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value Measurement - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill and intangible impairment	$ 0	$ 0	$ 0
Equity securities without readily determinable fair value, impairment	0
Equity securities without readily determinable fair value, upward adjustment	0
Equity securities without readily determinable fair value, downward adjustment	0
Remaining outstanding	69,000,000	61,200,000
Contract manufacturer deposit (non-interest bearing)	23,900,000	0
Long-term trade accounts receivable	15,000,000
Junos Pulse
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Remaining outstanding	69,000,000	61,200,000
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	2,158,700,000	2,252,900,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability measured at non-recurring basis	7,100,000	1,800,000
Fair Value, Measurements, Recurring | Significant Other Unobservable Remaining Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability measured at non-recurring basis	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Remaining Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability measured at non-recurring basis	7,100,000	1,800,000
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability measured at non-recurring basis	0	$ 0
Privately-held debt and redeemable preferred stock securities | Fair Value, Measurements, Recurring | Significant Other Unobservable Remaining Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss) on investments	$ 0

Derivative Instruments - Notion

Derivative Instruments - Notional Amount (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivative	$ 656.4	$ 629.4
Non-designated derivatives
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivative	158.7	108.3
Cash flow hedges | Designated as hedge
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivative	$ 497.7	$ 521.1

Derivative Instruments - Narrat

Derivative Instruments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Foreign exchange contracts | Cost of revenues and operating expenses
Derivatives, Fair Value [Line Items]
Changes in fiar value of non-designated derivatives	$ 7.6	$ 1.8	$ 0.5
Cash flow hedges | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in other comprehensive income (loss), Effective portion	(8.7)	20.2	(1.3)
Ineffective portion	0	0	0
Cash flow hedges | Foreign exchange contracts | Cost of revenues and operating expenses
Derivatives, Fair Value [Line Items]
Gain (loss) reclassified	$ 0.9	$ 7.6	$ 1.8
Designated as hedge | Cash flow hedges
Derivatives, Fair Value [Line Items]
Maturities of cash flow hedge derivatives	17 months
Losses expected to be reclassified into earnings within the next 12 months	$ 1.6

Goodwill and Purchased Intang_3

Goodwill and Purchased Intangible Assets - GoodwillRollforward (Details)	12 Months Ended
	Dec. 31, 2018USD ($)Reportable_Segment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Goodwill [Roll Forward]
Goodwill, beginning of period	$ 3,096,200,000	$ 3,081,700,000
Additions due to business combination	14,400,000	16,700,000
Other	(1,800,000)	(2,200,000)
Goodwill, end of period	$ 3,108,800,000	3,096,200,000	$ 3,081,700,000
Number of reporting units | Reportable_Segment	3
Goodwill impairment	$ 0	$ 0	$ 0

Goodwill and Purchased Intang_4

Goodwill and Purchased Intangible Assets - Purchased Intangible Assets, Net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Purchased Intangible Assets [Line Items]
Gross	$ 733,700,000	$ 725,900,000
Accumulated amortization	611,500,000	594,100,000
Impairment and other charges	(52,700,000)	(52,700,000)
Net	69,500,000	79,100,000
Total purchased intangible assets, gross	782,700,000	774,900,000
Purchased intangible assets, net	118,500,000	128,100,000
Amortization of intangible assets	17,400,000	17,500,000	$ 16,300,000
Impairment of intangible assets	0	0	$ 0
IPR&D
Purchased Intangible Assets [Line Items]
Indefinite-lived intangible assets:	49,000,000	49,000,000
Technologies and patents
Purchased Intangible Assets [Line Items]
Gross	648,100,000	640,300,000
Accumulated amortization	534,000,000	518,100,000
Impairment and other charges	(49,900,000)	(49,900,000)
Net	64,200,000	72,300,000
Customer contracts, support agreements, and related relationships
Purchased Intangible Assets [Line Items]
Gross	83,600,000	83,600,000
Accumulated amortization	75,500,000	74,100,000
Impairment and other charges	(2,800,000)	(2,800,000)
Net	5,300,000	6,700,000
Other
Purchased Intangible Assets [Line Items]
Gross	2,000,000	2,000,000
Accumulated amortization	2,000,000	1,900,000
Impairment and other charges	0	0
Net	$ 0	$ 100,000

Goodwill and Purchased Intang_5

Goodwill and Purchased Intangible Assets - Estimated Future Amortization Expense Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2,019	$ 25.1
2,020	17.2
2,021	12.9
2,022	7.7
2,023	5.3
Thereafter	1.3
Net	$ 69.5	$ 79.1

Other Financial Information - I

Other Financial Information - Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Other Financial Information [Abstract]
Production materials	$ 60.6	$ 71.2
Finished goods	21.4	26.6
Inventory	82	97.8
Schedule Of Inventory [Line Items]
Inventory	82	97.8
Prepaid expenses and other current assets
Other Financial Information [Abstract]
Inventory	80.6	93.8
Schedule Of Inventory [Line Items]
Inventory	80.6	93.8
Other long-term assets
Other Financial Information [Abstract]
Inventory	1.4	4
Schedule Of Inventory [Line Items]
Inventory	$ 1.4	$ 4

Other Financial Information - P

Other Financial Information - Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property and Equipment [Line Items]
Contract with Customer, Liability	$ 1,213.6	$ 1,539.3
Property and equipment, gross	2,124.1	2,223.3
Accumulated depreciation	(1,172.4)	(1,202.2)
Property and equipment, net	951.7	1,021.1
Depreciation expense	193.2	202.8	$ 184.5
Computers and equipment
Property and Equipment [Line Items]
Property and equipment, gross	1,100	1,151.7
Software
Property and Equipment [Line Items]
Property and equipment, gross	223.3	217.8
Leasehold improvements
Property and Equipment [Line Items]
Property and equipment, gross	235.2	258.6
Furniture and fixtures
Property and Equipment [Line Items]
Property and equipment, gross	48.6	47.9
Building and building improvements
Property and Equipment [Line Items]
Property and equipment, gross	254.3	252.8
Land and land improvements
Property and Equipment [Line Items]
Property and equipment, gross	243.2	241
Construction-in-process
Property and Equipment [Line Items]
Property and equipment, gross	$ 19.5	$ 53.5

Other Financial Information - N

Other Financial Information - Note Receivable and Deposit (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Other Financial Information [Abstract]
Pulse Note (including accumulated interest paid in kind)	$ 69	$ 61.2
Contract manufacturer deposit (non-interest bearing)	23.9	0
Total	$ 92.9	$ 61.2

Other Financial Information -_2

Other Financial Information - Notes Receivable and Deposit, Revenue, Deferred Commissions Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 31, 2019	Oct. 01, 2014
Disaggregation of Revenue [Line Items]
Proceeds from Pulse note receivable		$ 0	$ 75,000,000	$ 0
Pulse Note (including accumulated interest paid in kind)	$ 69,000,000	69,000,000	61,200,000
Non-interest bearing deposit to contract manufacturer	25,000,000	25,000,000
Non-interest bearing deposit to contract manufacturer, unamortized discount	$ 1,100,000	1,100,000
Non-interest bearing deposit to contract manufacturer, imputed interest rate	4.80%
Impairment charge, notes receivable		0	0	0
Deferred commission	$ 33,700,000	33,700,000
Amortization of deferred commission		144,200,000
Impairment loss		0
Product
Disaggregation of Revenue [Line Items]
Contract with customer, liability, revenue recognized		104,200,000
Service
Disaggregation of Revenue [Line Items]
Contract with customer, liability, revenue recognized		690,300,000
Junos Pulse
Disaggregation of Revenue [Line Items]
Promissory note						$ 125,000,000
Proceeds from Pulse note receivable			75,000,000
Pulse Note (including accumulated interest paid in kind)	$ 69,000,000	69,000,000	61,200,000
Interest income		$ 8,400,000	$ 8,300,000	$ 10,600,000
Forecast | Subsequent Event
Disaggregation of Revenue [Line Items]
Non-interest bearing deposit to contract manufacturer					$ 22,000,000

Other Financial Information - W

Other Financial Information - Warranties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Warranty Reserve [Roll Forward]
Beginning balance	$ 27.4	$ 41.3
Provisions made during the period, net	30.7	36.7
Actual costs incurred during the period	(30.1)	(50.6)
Ending balance	$ 28	$ 27.4

Other Financial Information - D

Other Financial Information - Deferred Revenue (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Deferred product revenue:
Deferred revenue	$ 1,213.6		$ 1,539.3
Reported as:
Deferred revenue	829.3	$ 804.9	1,030.3
Long-term deferred revenue	384.3	$ 384.4	509
Undelivered Product Commitments and Other Product Deferrals [Member]
Deferred product revenue:
Deferred revenue, gross	163.3		312.6
Distributor Inventory and Other Sell-through Items [Member]
Deferred product revenue:
Deferred revenue, gross	0		68.1
Product
Deferred product revenue:
Deferred revenue, gross	163.3		380.7
Deferred cost	18.9		46.5
Deferred revenue	144.4		334.2
Service
Deferred product revenue:
Deferred revenue	$ 1,069.2		$ 1,205.1

Other Financial Information - R

Other Financial Information - Revenue, Remaining Performance Obligation (Details) $ in Millions	Dec. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 848.3
Revenue recognition expected by period, satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 321.7
Revenue recognition expected by period, satisfaction period	2 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 62.5
Revenue recognition expected by period, satisfaction period
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 1,232.5
Product | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 131.2
Revenue recognition expected by period, satisfaction period	1 year
Product | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 28.9
Revenue recognition expected by period, satisfaction period	2 years
Product | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 3.2
Revenue recognition expected by period, satisfaction period
Product | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 163.3
Service | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 717.1
Revenue recognition expected by period, satisfaction period	1 year
Service | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 292.8
Revenue recognition expected by period, satisfaction period	2 years
Service | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 59.3
Revenue recognition expected by period, satisfaction period
Service | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Disaggregation of Revenue [Line Items]
Revenue recognition expected by period	$ 1,069.2

Other Financial Information - O

Other Financial Information - Other Expense, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Financial Information [Abstract]
Interest income	$ 72.7	$ 53	$ 35.4
Interest expense	(103.2)	(101.2)	(97.7)
(Loss) gain on investments, net	(7.4)	14.6	(1.8)
Other	(1.6)	(2.7)	1.8
Other expense, net	$ (39.5)	$ (36.3)	$ (62.3)

Restructuring Charges - Include

Restructuring Charges - Included in Cost of Revenues and Restructuring and Other Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring charges (benefits)	$ 7.3	$ 65.6	$ 3.3
Restructuring charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges (benefits)	7.3	65.6	3.3
Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges (benefits)	8.3	57.7	2.8
Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring charges (benefits)	0	0	0.5
Contract terminations
Restructuring Cost and Reserve [Line Items]
Restructuring charges (benefits)	$ (1)	$ 7.9	$ 0

Restructuring Charges - Narrati

Restructuring Charges - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 5
2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 3.3

Restructuring Charges - Roll-fo

Restructuring Charges - Roll-forward (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance		$ 20
Charges/(Benefits)	$ 36.2	7.3	$ 65.6	$ 3.3
Cash Payments		(26.3)
Other		0.1
Restructuring liability, ending balance	20		20
2017 Restructuring Plan
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance
Restructuring liability, ending balance		1.1
2017 Restructuring Plan | Severance
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance		17.7
Charges/(Benefits)		8.3
Cash Payments		(25)
Other		0.1
Restructuring liability, ending balance	17.7	1.1	17.7
2017 Restructuring Plan | Contract terminations
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance		2.3
Charges/(Benefits)		(1)
Cash Payments		(1.3)
Other		0
Restructuring liability, ending balance	$ 2.3	$ 0	$ 2.3

Debt and Financing - Shedule of

Debt and Financing - Shedule of Debt (Details) $ in Millions	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 2,150
Unaccreted discount and debt issuance costs	(11)
Total	2,139
3.125% fixed-rate notes (2019 Notes)
Debt Instrument [Line Items]
Long-term debt	$ 350
Stated interest rate	3.125%
Effective interest rate	3.36%
3.300% fixed-rate notes (2020 Notes)
Debt Instrument [Line Items]
Long-term debt	$ 300
Stated interest rate	3.30%
Effective interest rate	3.47%
4.600% fixed-rate notes
Debt Instrument [Line Items]
Long-term debt	$ 300
Stated interest rate	4.60%
Effective interest rate	4.69%
4.500% fixed-rate notes (2024 Notes)
Debt Instrument [Line Items]
Long-term debt	$ 350
Stated interest rate	4.50%
Effective interest rate	4.63%
4.500% fixed-rate notes (2024 Notes)
Debt Instrument [Line Items]
Long-term debt	$ 150
Stated interest rate	4.50%
Effective interest rate	4.87%
4.350% fixed-rate notes (2025 Notes)
Debt Instrument [Line Items]
Long-term debt	$ 300
Stated interest rate	4.35%
Effective interest rate	4.47%
5.950% fixed-rate notes
Debt Instrument [Line Items]
Long-term debt	$ 400
Stated interest rate	5.95%
Effective interest rate	6.03%

Debt and Financing - Schedule o

Debt and Financing - Schedule of Aggregate Debt Maturities (Details) $ in Millions	Dec. 31, 2018USD ($)
Debt Disclosure [Abstract]
2,019	$ 350
2,020	300
2,021	300
2,022	0
2,023	0
Thereafter	1,200
Total	$ 2,150

Debt and Financing - Narrative

Debt and Financing - Narrative (Details) - USD ($)	Jun. 27, 2014	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Repurchase price percentage related to change in control		101.00%
Financing Arrangements [Abstract]
Sale of receivables		$ 122,800,000	$ 169,400,000	$ 95,600,000
Proceeds from sale and collection of receivables		123,200,000	169,300,000	$ 83,200,000
Receivables from sale of receivables		17,200,000	13,700,000
Cash received from financing provider		$ 0	$ 16,900,000
Minimum
Financing Arrangements [Abstract]
Number of days due from receivable		1 day
Maximum
Financing Arrangements [Abstract]
Number of days due from receivable		90 days
Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 500,000,000
Additional borrowing capacity	$ 200,000,000
Revolving Credit Facility | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Revolving Credit Facility | ICE Benchmark Administration Settlement Rate
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Revolving Credit Facility | Minimum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
Revolving Credit Facility | Minimum | Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate	0.90%
Revolving Credit Facility | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Revolving Credit Facility | Maximum | Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
3.300% fixed-rate notes (2020 Notes)
Debt Instrument [Line Items]
Debt instrument, redemption, redemption period		1 month
4.350% fixed-rate notes (2025 Notes)
Debt Instrument [Line Items]
Debt instrument, redemption, redemption period		3 months
Other Fixed Rate Notes
Debt Instrument [Line Items]
Debt instrument, redemption price, percent		100.00%
One Month Prior to Maturity | 3.300% fixed-rate notes (2020 Notes) | Treasury Rate
Debt Instrument [Line Items]
Debt instrument, redemption, discount rate, basis spread on variable rate		0.30%
One Month Prior to Maturity | 4.350% fixed-rate notes (2025 Notes) | Treasury Rate
Debt Instrument [Line Items]
Debt instrument, redemption, discount rate, basis spread on variable rate		0.375%
One Month Prior to Maturity | Fixed Rate Notes Due 2020 And 2025
Debt Instrument [Line Items]
Debt instrument, redemption price, percent		100.00%
Any Time on or After May 15, 2020 | 3.300% fixed-rate notes (2020 Notes)
Debt Instrument [Line Items]
Debt instrument, redemption price, percent		100.00%
Any Time on or After May 15, 2020 | 4.350% fixed-rate notes (2025 Notes)
Debt Instrument [Line Items]
Debt instrument, redemption price, percent		100.00%

Equity - Stock Repurchase Activ

Equity - Stock Repurchase Activities (Details) $ / shares in Units, shares in Millions	Dec. 26, 2018$ / shares	Oct. 24, 2018$ / shares	Sep. 25, 2018$ / shares	Jul. 26, 2018$ / shares	Jun. 22, 2018$ / shares	May 02, 2018$ / shares	Mar. 22, 2018$ / shares	Jan. 30, 2018$ / shares	Dec. 31, 2018USD ($)shares	Mar. 31, 2018USD ($)shares	Dec. 31, 2018USD ($)Dividend$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Feb. 28, 2018USD ($)	Jan. 31, 2018USD ($)
Dividends
Per Share (in dollars per share) | $ / shares	$ 0.18		$ 0.18		$ 0.18		$ 0.18				$ 0.72	$ 0.40	$ 0.40
Amount											$ 249,300,000	$ 150,400,000	$ 152,500,000
Stock Repurchase Program
Number of quarterly cash dividends declared | Dividend											4
Cash dividends declared per share of common stock (in dollars per share) | $ / shares		$ 0.18		$ 0.18		$ 0.18		$ 0.18
Cash dividends paid per share of common stock (in dollars per share) | $ / shares	$ 0.18		$ 0.18		$ 0.18		$ 0.18				$ 0.72	$ 0.40	$ 0.40
Payment to repurchase stock											$ 756,600,000	$ 725,800,000	$ 324,600,000
Stock Repurchase Program 2018
Stock Repurchase Program
Shares (in shares) | shares											29.3
Average price per share (in dollars per share) | $ / shares											$ 25.62
Amount											$ 750,000,000
Tax Withholding Amount											6,600,000
Total of Dividends and Stock Repurchase Program, Amount											1,005,900,000
Stock repurchase program, authorized amount															$ 2,000,000,000
Stock repurchase program, authorized funds remaining									$ 1,300,000,000		$ 1,300,000,000
Accelerated Share Repurchase Program
Stock Repurchase Program
Shares (in shares) | shares									6	23.3	29.3	26.1
Average price per share (in dollars per share) | $ / shares											$ 25.62	$ 27.61
Amount												$ 719,700,000
Tax Withholding Amount												6,100,000
Total of Dividends and Stock Repurchase Program, Amount												$ 876,200,000
Stock repurchase program, authorized amount														$ 750,000,000	$ 750,000,000
Payment to repurchase stock										$ 750,000,000
Stock Repurchase Program 2014
Stock Repurchase Program
Shares (in shares) | shares													13.5
Average price per share (in dollars per share) | $ / shares													$ 23.25
Amount													$ 312,900,000
Tax Withholding Amount													11,700,000
Total of Dividends and Stock Repurchase Program, Amount													$ 477,100,000

Equity - Accumulated Other Comp

Equity - Accumulated Other Comprehensive Income, Net of Tax (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Other comprehensive income before reclassifications		$ 39.2	$ (15.8)
Amount reclassified from accumulated other comprehensive loss		(7.3)	(2.3)
Other comprehensive income, net		31.9	(18.1)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Balance at beginning of period	$ (5.4)	(37.3)	(19.2)
Other comprehensive income before reclassifications	(18.2)
Amount reclassified from accumulated other comprehensive loss	(0.3)
Reclassification of tax effects upon adoption of ASU 2018-02	5.7
Other comprehensive income, net	(18.5)
Balance at end of period	(18.2)	(5.4)	(37.3)
Unrealized Gains on Available-for- Sale Securities
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Balance at beginning of period	19	16.6	17
Other comprehensive income before reclassifications	0.6	4.5	0.8
Amount reclassified from accumulated other comprehensive loss	0.9	(2.1)	(1.2)
Reclassification of tax effects upon adoption of ASU 2018-02	5
Other comprehensive income, net	1.5	2.4	(0.4)
Balance at end of period	25.5	19	16.6
Unrealized Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Balance at beginning of period	6	(4.5)	(1.3)
Other comprehensive income before reclassifications	(6.4)	15.7	(2.1)
Amount reclassified from accumulated other comprehensive loss	(1.2)	(5.2)	(1.1)
Reclassification of tax effects upon adoption of ASU 2018-02	0.7
Other comprehensive income, net	(7.6)	10.5	(3.2)
Balance at end of period	(0.9)	6	(4.5)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Balance at beginning of period	(30.4)	(49.4)	(34.9)
Other comprehensive income before reclassifications	(12.4)	19	(14.5)
Amount reclassified from accumulated other comprehensive loss	0	0	0
Reclassification of tax effects upon adoption of ASU 2018-02	0
Other comprehensive income, net	(12.4)	19	(14.5)
Balance at end of period	$ (42.8)	$ (30.4)	$ (49.4)

Employee Benefit Plans - Equity

Employee Benefit Plans - Equity Incentive Plans (Details)	Nov. 06, 2017period	May 31, 2017shares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017shares	May 19, 2015shares
Share-Based Compensation Plans
Additional shares authorized (in shares)		23,000,000
Number of shares available for future issuance (in shares)				33,500,000
ESPP, offering period (in months)	24 months
ESPP, Number of offering period | period	4
ESPP, Purchase period (in months)	6 months
ESPP, Purchase price (in percentage)	85.00%
Common stock - shares issued (in shares)			346,400,000	365,500,000
Common shares outstanding from equity awards through acquisition (in shares)			2,200,000
Various Acquisitions
Share-Based Compensation Plans
Common shares outstanding from equity awards through acquisition (in shares)			4,100,000
Equity Incentive Plan 2015
Share-Based Compensation Plans
Number of shares authorized (in shares)					38,000,000
Additional shares authorized (in shares)			0
Number of shares available for future issuance (in shares)			21,900,000
Equity Incentive Plan 1996 and 2006
Share-Based Compensation Plans
Maximum additional shares expire unexercised, under 1996 and 2000 plan (in shares)					29,000,000
Number of shares available for future issuance (in shares)				0
Equity Incentive Plan 2015 and 2006
Share-Based Compensation Plans
Aggregate shares subject to outstanding equity awards			15,300,000
Employee Stock Purchase Plan 2008
Share-Based Compensation Plans
Number of shares authorized (in shares)			35,000,000
Number of shares available for future issuance (in shares)			8,700,000
Discount on share purchase price for purchases made under ESPP			15.00%
Periodic payroll deduction - percentage of base salary			10.00%
ESPP individual purchase limits (in shares)			6,000
Period for share purchases under ESPP			12 months
ESPP individual purchase limits | $			$ 25,000
Period for ESPP purchases			1 year
Common stock - shares issued (in shares)			26,300,000

Employee Benefit Plans - RSU, R

Employee Benefit Plans - RSU, RSA, and PSA Activities (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted Average Grant-Date Fair Value per Share
Fair value of RSUs, RSAs and PSAs	$ 200.5	$ 187.3	$ 185.7
Restricted Stock Units (RSU) and Restricted Stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Restricted Stock Units (RSUs)
Number of Shares
Granted (in shares)	7.4
Substituted in acquisitions (in shares)	0.1
Vested (in shares)	(6.5)
Canceled (in shares)	(2)
Weighted Average Grant-Date Fair Value per Share
Granted (in dollars per share)	$ 25.40
Substituted in acquisitions (in dollars per share)	26.26
Vested (in dollars per share)	25.67
Canceled (in dollars per share)	25.92
Balance at end of period (in dollars per share)	$ 25.33
Performance Shares (PSAs)
Number of Shares
Granted (in shares)	0.9
Vested (in shares)	(1.1)
Canceled (in shares)	(0.8)
Weighted Average Grant-Date Fair Value per Share
Granted (in dollars per share)	$ 24.62
Vested (in dollars per share)	24.14
Canceled (in dollars per share)	24.45
Balance at end of period (in dollars per share)	$ 24.66
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options,Performance Goal, Number of Shares	0.7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Number of Shares Modified	1.9
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	$ 6.9
Performance Shares (PSAs) | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	2 years
Weighted Average Grant-Date Fair Value per Share
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options,Performance Goal, Number of Shares	0
Performance Shares (PSAs) | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Weighted Average Grant-Date Fair Value per Share
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options,Performance Goal, Number of Shares	1
RSA
Number of Shares
Substituted in acquisitions (in shares)	0.1
Vested (in shares)	(0.2)
Weighted Average Grant-Date Fair Value per Share
Substituted in acquisitions (in dollars per share)	$ 27.66
Vested (in dollars per share)	25.12
Balance at end of period (in dollars per share)	$ 27.53
RSUs, RSAs, and PSAs
Number of Shares
Balance at beginning of period (in shares)	19.5
Balance at end of period (in shares)	17.4	19.5
Weighted Average Grant-Date Fair Value per Share
Balance at beginning of period (in dollars per share)	$ 25.39
Balance at end of period (in dollars per share)	$ 25.32	$ 25.39
Weighted Average Remaining Contractual Term (In Years)	11 months 26 days
Aggregate Intrinsic Value	$ 467.6
Vested and Expected-to-Vest RSUs and PSAs, Number of Shares at Period End	15.5
Vested and Expected-to-Vest RSUs and PSAs, Grant Date Fair Value (in USD per share)	$ 25.31
Vested and Expected-to-Vest Options, Weighted Average Remaining Contractual Term at Period End	1 year
Vested and Expected-to-Vest RSUs and PSAs, Aggregate Intrinsic Value	$ 418.4

Employee Benefit Plans - Shares

Employee Benefit Plans - Shares Available For Grant (Details) - shares shares in Millions	1 Months Ended	12 Months Ended
	May 31, 2017	Dec. 31, 2018
Shares Available For Grant
Balance as of beginning of period (in shares)		33.5
Additional shares authorized (in shares)	23
Equity Incentive Plan 2015
Shares Available For Grant
Additional shares authorized (in shares)		0
RSUs and PSAs granted (in shares)		(17.7)
RSUs and PSAs canceled (in shares)		5.4
Options canceled/expired (in shares)		0.7
Balance as of end of period (in shares)		21.9

Employee Benefit Plans - Employ

Employee Benefit Plans - Employee Stock Purchase Plan and Valuation Assumptions (Details) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Stock Purchase Plan
Estimates of Fair Value
Volatility	29.00%	25.00%	32.00%
Risk-free interest rate	1.90%	0.90%	0.40%
Expected life (years)	1 year 2 months 30 days	6 months	6 months
Dividend yield	2.70%	1.50%	1.80%
Weighted-average fair value per share	$ 6.93	$ 6.04	$ 5.56
Market-based RSUs
Estimates of Fair Value
Volatility	28.00%	30.00%	36.00%
Risk-free interest rate	2.40%	1.90%	1.20%
Dividend yield	2.60%	1.40%	1.70%
Weighted-average fair value per share	$ 28.39	$ 19.30	$ 14.71
Employee Stock Purchase Plan 2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares purchased through ESPP (in shares)	2.5	2.7	2.7
Average exercise price of shares purchased through ESPP (in dollar per share)	$ 22.31	$ 20.83	$ 19.66

Employee Benefit Plans - Share-

Employee Benefit Plans - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	$ 217.1	$ 187.5	$ 226.8
Stock Options
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	0.4	0.5	4.4
RSUs, RSAs, and PSAs
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	198.2	171.3	206.9
Employee Stock Purchase Plan
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	18.5	15.7	15.5
Cost of Revenues, Product
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	6.3	4.6	6.4
Cost of Revenues, Service
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	18	17.5	15.3
Research and Development Expense
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	120.6	86.6	126.5
Selling and Marketing Expense
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	51.1	55.6	55.2
General and Administrative Expense
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	$ 21.1	$ 23.2	$ 23.4

Employee Benefit Plans - Shar_2

Employee Benefit Plans - Share-Based Compensation Expense Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company recognized tax benefits on total stock-based compensation expense	$ 33.8	$ 29.1	$ 53.3
Tax benefit realized related to awards vested or exercised during the period	38.9	$ 64.1	$ 58.6
Unrecognized compensation cost	$ 280.4
RSUs, RSAs, and PSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period that unrecognized compensation cost will be recognized	1 year 4 months 24 days

Employee Benefit Plans - 401(k)

Employee Benefit Plans - 401(k) plan, Deferred Compensation Plan and Non-US Pension Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Benefit Textuals [Abstract]
Employee Contribution Matched in Percent	30.00%
Matching Contributions to Plan	$ 20.2	$ 21.1	$ 20.7
Fair value of the Pension Plans	13.1	11.3
Net plan liability	2.5	4.3
NQDC
Employee Benefit Textuals [Abstract]
Deferred compensation liability	24.3	27.6
Investment	24.3	27.6
Prepaid expenses and other current assets | NQDC
Employee Benefit Textuals [Abstract]
Investment	3.6	4.9
Other long-term assets | NQDC
Employee Benefit Textuals [Abstract]
Investment	20.7	22.7
Other accrued liabilities | NQDC
Employee Benefit Textuals [Abstract]
Deferred compensation liability	3.6	4.9
Other long-term liabilities | NQDC
Employee Benefit Textuals [Abstract]
Deferred compensation liability	$ 20.7	$ 22.7

Segments - Revenue (Details)

Segments - Revenue (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)Customersegment	Dec. 31, 2017USD ($)Customer	Dec. 31, 2016USD ($)Customer
Segment Reporting Information [Line Items]
Number of reportable segments | segment									1
Net Revenues [Abstract]
Net revenues	$ 1,181	$ 1,179.8	$ 1,204.1	$ 1,082.6	$ 1,239.5	$ 1,257.8	$ 1,308.9	$ 1,221	$ 4,647.5	$ 5,027.2	$ 4,990.1
Number of customers accounting for more than 10% of revenues | Customer									0	0	0
Routing
Net Revenues [Abstract]
Net revenues									$ 1,839.7	$ 2,189.5	$ 2,352.9
Switching
Net Revenues [Abstract]
Net revenues									934.4	963.4	858
Security
Net Revenues [Abstract]
Net revenues									333	293.3	318
Product
Net Revenues [Abstract]
Net revenues									3,107.1	3,446.2	3,528.9
Service
Net Revenues [Abstract]
Net revenues									1,540.4	1,581	1,461.2
Cloud
Net Revenues [Abstract]
Net revenues									1,049.9	1,310.7	1,315.9
Service Provider
Net Revenues [Abstract]
Net revenues									2,066.7	2,319.4	2,316.4
Enterprise
Net Revenues [Abstract]
Net revenues									$ 1,530.9	$ 1,397.1	$ 1,357.8

Segments - Geographical (Detail

Segments - Geographical (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net Revenues by Geographic Region [Line Items]
Property and equipment, net and purchased intangible assets, net	$ 1,070.2				$ 1,149.2				$ 1,070.2	$ 1,149.2
Net revenues	1,181	$ 1,179.8	$ 1,204.1	$ 1,082.6	1,239.5	$ 1,257.8	$ 1,308.9	$ 1,221	4,647.5	5,027.2	$ 4,990.1
Total Americas
Net Revenues by Geographic Region [Line Items]
Net revenues									2,541.2	2,947.2	2,968.8
United States
Net Revenues by Geographic Region [Line Items]
Property and equipment, net and purchased intangible assets, net	941.7				1,005.1				941.7	1,005.1
Net revenues									2,339.1	2,712.6	2,737
Other
Net Revenues by Geographic Region [Line Items]
Net revenues									202.1	234.6	231.8
Europe, Middle East, and Africa
Net Revenues by Geographic Region [Line Items]
Net revenues									1,290.8	1,195.8	1,238.1
Asia Pacific
Net Revenues by Geographic Region [Line Items]
Net revenues									815.5	884.2	$ 783.2
Total
Net Revenues by Geographic Region [Line Items]
Property and equipment, net and purchased intangible assets, net	$ 128.5				$ 144.1				$ 128.5	$ 144.1

Income Taxes - Components of In

Income Taxes - Components of Income Tax (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory rate									21.00%	35.00%	35.00%
Components of income before provision for income taxes and noncontrolling interest
Domestic									$ 160.6	$ 474.2	$ 466.2
Foreign									372.1	337.6	361.2
Income before income taxes	$ 188.4	$ 152	$ 150.9	$ 41.4	$ 200.2	$ 225.8	$ 245.2	$ 140.6	532.7	811.8	827.4
Current (benefit) provision:
Federal									(126.1)	594.3	121.4
States									9	13.9	10.3
Foreign									38.9	45.4	46
Total current (benefit) provision									(78.2)	653.6	177.7
Deferred (benefit) provision:
Federal									36.6	(128.7)	57.2
States									2.2	(17.7)	4.3
Foreign									5.2	(1.6)	(4.5)
Total deferred (benefit) provision									44	(148)	57
Total (benefit) provision for income taxes									(34.2)	505.6	234.7
Income tax reconciliation
Expected provision at 35% rate									111.9	284.1	289.6
State taxes, net of federal benefit									7.4	12	8.9
Foreign income at different tax rates									(12.8)	(46.4)	(53.4)
R&D tax credits									(22.1)	(15.1)	(16.8)
Share-based compensation									4.7	0	10.5
Release of valuation allowance									0	(1.7)	(0.7)
Domestic production activities									0	(12.4)	(9.5)
Non-deductible compensation									1.9	1.6	2.4
Impact of the U.S. Tax Cuts and Jobs Act									2.8	289.5	0
Tax accounting method changes									(65.4)	0	0
Lapses in federal statutes of limitations									67.6	0	0
Other									5	(6)	3.7
Total (benefit) provision for income taxes									(34.2)	505.6	$ 234.7
Schedule Of Income Taxes [Line Items]
Provisional income tax change					$ 289.5					$ 289.5
Product
Schedule Of Income Taxes [Line Items]
Reduction of expected tax liabilities, change in accounting method for tax recognition of deferred revenue									33.2
Service
Schedule Of Income Taxes [Line Items]
Reduction of expected tax liabilities, change in accounting method for tax recognition of deferred revenue									$ 32.2

Income Taxes - Deferred Taxes (

Income Taxes - Deferred Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carry-forwards	$ 12.9	$ 18.3
Research and other credit carry-forwards	220	198.8
Deferred revenue	37.7	103.5
Share-based compensation	26.1	31.1
Cost sharing adjustment	12.2	12.4
Reserves and accruals not currently deductible	62.7	76.7
Other	13.2	12.8
Total deferred tax assets	384.8	453.6
Valuation allowance	(233.7)	(214.5)
Deferred tax assets, net of valuation allowance	151.1	239.1
Deferred tax liabilities:
Property and equipment basis differences	(40.6)	(42.5)
Purchased intangibles	(13.7)	(12.4)
Unremitted foreign earnings	(26.4)	(25.4)
Deferred compensation and other	(8.9)	(10.4)
Total deferred tax liabilities	(89.6)	(90.7)
Net deferred tax assets	61.5	148.4
Valuation allowance	233.7	214.5
Increase (decrease) in DTA valuation allowance	19.2	$ 60.1
Federal
Deferred tax liabilities:
Net operating loss carry-forwards	54.4
Tax credit carry-forwards	2.6
California
Deferred tax liabilities:
Net operating loss carry-forwards	150.4
Tax credit carry-forwards	244.1
California Deferred Tax Assets
Deferred tax assets:
Valuation allowance	(206)
Deferred tax liabilities:
Valuation allowance	206
Net operating loss carry-forwards	150.4
Massachusetts Deferred Tax Assets
Deferred tax assets:
Valuation allowance	(20.2)
Deferred tax liabilities:
Valuation allowance	20.2
Canadian Deferred Tax Assets
Deferred tax assets:
Valuation allowance	(3.1)
Deferred tax liabilities:
Valuation allowance	3.1
Capital Loss Carryforward
Deferred tax assets:
Valuation allowance	(4.4)
Deferred tax liabilities:
Valuation allowance	$ 4.4

Income Taxes - Income Tax Conti

Income Taxes - Income Tax Contingencies (Details) - USD ($) $ in Millions	Nov. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate		$ 175.3
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year		264.5	$ 223.1	$ 216.1
Current Year [Abstract]
Additions		4.3	64.6	27.2
Prior Years [Abstract]
Additions		12.7	1.8	1
Reductions		(33.8)	(16.6)	(4.1)
Settlements		(2.6)	(4)	(14.3)
Lapses in statutes of limitations		(67)	(4.4)	(2.8)
Balance at end of year		178.1	264.5	223.1
Tax expense recognized for net interest and penalties in the Consolidated Statements of Operations		5.2	8.5	6
Previously unrecognized tax benefits, income tax examination	$ 5.4
income tax examination, interest and penalties	$ 4.6
State and Local Jurisdiction | California Franchise Tax Board
Prior Years [Abstract]
Reductions		(7.7)
Other Long Term Liabilities
Prior Years [Abstract]
Interest and penalties accrued related to unrecognized tax benefits		$ 33.8	$ 40.7	$ 31.3

Net Income per Share (Details)

Net Income per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income	$ 192.2	$ 223.8	$ 116.5	$ 34.4	$ (148.1)	$ 165.7	$ 179.8	$ 108.8	$ 566.9	$ 306.2	$ 592.7
Denominator:
Weighted-average shares used to compute basic net income per share									349	377.7	381.7
Dilutive effect of employee stock awards									5.4	6.5	6.1
Weighted-average shares used to compute diluted net income per share									354.4	384.2	387.8
Net income per share:
Basic (in dollars per share)	$ 0.56	$ 0.65	$ 0.33	$ 0.10	$ (0.40)	$ 0.44	$ 0.47	$ 0.29	$ 1.62	$ 0.81	$ 1.55
Diluted (in dollars per share)	$ 0.55	$ 0.64	$ 0.33	$ 0.10	$ (0.40)	$ 0.43	$ 0.47	$ 0.28	$ 1.60	$ 0.80	$ 1.53
Anti-dilutive shares excluded from computation of diluted earnings per share									3.9	1.1	2.5

Commitments and Contingencies -

Commitments and Contingencies - Commitments (Details) ft² in Thousands, $ in Millions	Jul. 10, 2015ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Unconditional Purchase Obligations
2,019		$ 43.1
2,020		26.4
2,021		11.4
2,022		8.5
2,023		5.5
Thereafter		2.9
Total		97.8
Operating Leases
2,019		33.7
2,020		30.7
2,021		24.3
2,022		17
2,023		14.3
Thereafter		26.3
Total		146.3
Other Lease Arrangement
2,019		13.1
2,020		13.3
2,021		13.6
2,022		13.9
2,023		14.2
Thereafter		32.9
Total		101
Rent expense		39	$ 39.3	$ 37.9
Property and equipment, net		951.7	1,021.1
Other lease arrangement		101
Purchase commitments		663.3
Accrual for estimated carrying charges or obsolete materials charges		30.4
Long-term debt		2,139
Remaining balance of transition tax obligation		245.2
Long-term income taxes payable		178.1	264.5	$ 223.1	$ 216.1
Long-term Income Taxes
Other Lease Arrangement
Long-term income taxes payable		159.2
Other Lease Arrangement
Other Lease Arrangement
Total		101
Square Feet of Leased Unit | ft²	63
Property and equipment, net			$ 60.9
Other lease arrangement		101
Other Lease Arrangement | Other long-term liabilities
Other Lease Arrangement
Total		59.7
Other lease arrangement		$ 59.7
Other Lease Arrangement | Maximum
Other Lease Arrangement
Lease Term		10 years
Master Service Agreement
Other Lease Arrangement
Master service agreement, expected amount		$ 325
Development, Testing and Related Work
Unconditional Purchase Obligations
Total		$ 18

Commitments and Contingencies_2

Commitments and Contingencies - Guarantees (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Indemnification Agreement
Guarantor Obligations [Line Items]
Guarantor obligations, current carrying value	$ 11.9	$ 20.4
Financing guarantees, bank guarantees, and standby letters of credit
Guarantor Obligations [Line Items]
Guarantor obligations, current carrying value	$ 23.1	$ 23

Commitments and Contingencies_3

Commitments and Contingencies - Legal Proceedings (Details) $ in Millions	Dec. 31, 2018USD ($)
Investigations by U.S. Securities and Exchange Commission and U.S. Department of Justice | Pending Litigation
Loss Contingencies [Line Items]
Estimated legal reserve	$ 12

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Selected Quarterly Financial Information [Abstract]
Net revenues	$ 1,181	$ 1,179.8	$ 1,204.1	$ 1,082.6	$ 1,239.5	$ 1,257.8	$ 1,308.9	$ 1,221	$ 4,647.5	$ 5,027.2	$ 4,990.1
Gross margin	710.9	711	700.9	618.4	751.2	772.4	801.9	746.6	2,741.2	3,072.1	3,104.5
Income before income taxes	188.4	152	150.9	41.4	200.2	225.8	245.2	140.6	532.7	811.8	827.4
Net income (loss)	$ 192.2	$ 223.8	$ 116.5	$ 34.4	$ (148.1)	$ 165.7	$ 179.8	$ 108.8	$ 566.9	$ 306.2	$ 592.7
Net income per share:
Basic (in dollars per share)	$ 0.56	$ 0.65	$ 0.33	$ 0.10	$ (0.40)	$ 0.44	$ 0.47	$ 0.29	$ 1.62	$ 0.81	$ 1.55
Diluted (in dollars per share)	$ 0.55	$ 0.64	$ 0.33	$ 0.10	$ (0.40)	$ 0.43	$ 0.47	$ 0.28	$ 1.60	$ 0.80	$ 1.53
Provisional income tax change					$ 289.5					$ 289.5
Restructuring charges					$ 36.2				$ 7.3	$ 65.6	$ 3.3

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 29, 2019	Oct. 24, 2018	Jul. 26, 2018	May 02, 2018	Jan. 30, 2018	Jan. 31, 2019	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Restructuring charges							$ 36.2	$ 7.3	$ 65.6	$ 3.3
Cash dividends declared per share of common stock (in dollars per share)		$ 0.18	$ 0.18	$ 0.18	$ 0.18
Subsequent Event
Subsequent Event [Line Items]
Cash dividends declared per share of common stock (in dollars per share)	$ 0.19
Minimum | Subsequent Event
Subsequent Event [Line Items]
Restructuring charges						$ 18
Maximum | Subsequent Event
Subsequent Event [Line Items]
Restructuring charges						$ 22

Schedule II- Valuation and Qu_2

Schedule II- Valuation and Qualifying Account (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 5.7	$ 7.6	$ 9.3
Charged to (Reversed from) Costs and Expenses	(0.8)	(2)	1
Write-offs, Net of Recoveries	0	0.1	(2.7)
Balance at End of Year	4.9	5.7	7.6
Sales return reserve	5.7	7.6	9.3
Sales Return Reserve
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	55.2	71.4	71.2
Charged as a Reduction in Revenues	70.7	25	44.6
Charged to Other Accounts	0	65.9	89.6
Used	(82.5)	(107.1)	(134)
Balance at End of Year	32.7	55.2	71.4
Sales return reserve	$ 55.2	$ 71.4	$ 71.2	$ 44.5
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09 | Sales Return Reserve
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Sales return reserve				$ (10.7)

Uncategorized Items - jnpr-2018

Label	Element	Value
Accounting Standards Update 2016-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 3,800,000
Accounting Standards Update 2016-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(9,000,000)
Accounting Standards Update 2016-09 [Member] | Common Stock Including Additional Paid in Capital [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 12,800,000