Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	May 04, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	JUNIPER NETWORKS INC
Entity Central Index Key	0001043604
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		349,152,345

Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net revenues:
Product	$ 710.8	$ 828.9
Service	371.8	392.1
Total net revenues	1,082.6	1,221.0
Revenue	1,082.6	1,221.0
Cost of revenues:
Product	306.4	330.2
Service	157.8	144.2
Total cost of revenues	464.2	474.4
Gross margin	618.4	746.6
Operating expenses:
Research and development	269.4	276.2
Sales and marketing	239.4	244.2
General and administrative	56.0	50.5
Restructuring (benefits) charges	(1.9)	19.4
Total operating expenses	562.9	590.3
Operating income	55.5	156.3
Other expense, net	(14.1)	(15.7)
Income before income taxes	41.4	140.6
Income tax provision	7.0	31.8
Net income	$ 34.4	$ 108.8
Net income per share:
Basic (in dollars per share)	$ 0.10	$ 0.29
Diluted, (in dollars per share)	$ 0.10	$ 0.28
Shares used in computing net income per share:
Basic (in shares)	355.3	380.9
Diluted (in shares)	360.6	388.0
Cash dividends declared per common stock (in dollars per share)	$ 0.18	$ 0.10

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 34.4	$ 108.8
Available-for-sale debt securities:
Unrealized (loss) gain, net of tax benefit of $1.4 and tax provision $0.7, respectively	(2.0)	1.5
Reclassification adjustment for realized net loss (gain) included in net income, net of tax provisions of zero for each period	0.9	(0.1)
Net change on available-for-sale debt securities, net of tax	(1.1)	1.4
Cash flow hedges:
Unrealized gains, net of tax provisions of $0.3 and $1.7, respectively	13.1	5.3
Reclassification adjustment for realized net (gain) loss included in net income, net of tax provisions of $0.6 and $0.3, respectively	(5.1)	1.1
Net change on cash flow hedges, net of tax	8.0	6.4
Change in foreign currency translation adjustments	5.3	7.9
Other comprehensive income, net of tax	12.2	15.7
Comprehensive income	$ 46.6	$ 124.5

Condensed Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Unrealized (loss) gain, net of tax benefit of $1.4 and tax provision $0.7, respectively	$ 1.4	$ (0.7)
Reclassification adjustment for realized net loss (gain) included in net income, net of tax provisions of zero for each period	0.0	0.0
Unrealized gains, net of tax provisions of $0.3 and $1.7, respectively	(0.3)	(1.7)
Reclassification adjustment for realized net (gain) loss included in net income, net of tax provisions of $0.6 and $0.3, respectively	$ 0.6	$ 0.3

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 2,614.2	$ 2,006.5
Short-term investments	317.7	1,026.1
Accounts receivable, net of allowances	679.9	852.0
Prepaid expenses and other current assets	308.9	299.9
Total current assets	3,920.7	4,184.5
Property and equipment, net	1,013.8	1,021.1
Long-term investments	516.5	988.4
Purchased intangible assets, net	123.8	128.1
Goodwill	3,096.2	3,096.2
Other long-term assets	407.5	415.5
Total assets	9,078.5	9,833.8
Current liabilities:
Accounts payable	189.2	217.6
Accrued compensation	172.8	186.0
Deferred revenue	888.2	1,030.3
Short-term debt	349.3	0.0
Other accrued liabilities	230.5	304.3
Total current liabilities	1,830.0	1,738.2
Long-term debt	1,787.7	2,136.3
Long-term deferred revenue	368.7	509.0
Long-term income taxes payable	649.5	650.6
Other long-term liabilities	117.9	118.8
Total liabilities	4,753.8	5,152.9
Commitments and contingencies (Note 14)
Stockholders' equity:
Convertible preferred stock, $0.00001 par value; 10.0 shares authorized; none issued and outstanding	0.0	0.0
Common stock, $0.00001 par value; 1,000.0 shares authorized; 349.0 shares and 365.5 shares issued and outstanding as of March 31, 2018 and December 31, 2017, respectively	0.0	0.0
Additional paid-in capital	7,615.5	8,042.1
Accumulated other comprehensive income (loss)	12.5	(5.4)
Accumulated deficit	(3,303.3)	(3,355.8)
Total stockholders' equity	4,324.7	4,680.9
Total liabilities and stockholders' equity	$ 9,078.5	$ 9,833.8

Condensed Consolidated Balance Sheets (Parentheticals) (Unaudited) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Convertible preferred stock - par value (in dollars per share)	$ 0.00001	$ 0.00001
Convertible preferred stock - shares authorized (shares)	10,000,000	10,000,000
Convertible preferred stock - issued (shares)	0	0
Convertible preferred stock - outstanding (shares)	0	0
Common stock - par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock - shares authorized (shares)	1,000,000,000	1,000,000,000
Common stock - issued (shares)	349,000,000	365,500,000
Common stock - outstanding (shares)	349,000,000	365,500,000

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income	$ 34.4	$ 108.8
Adjustments to reconcile net income to net cash provided by operating activities:
Share-based compensation expense	70.4	62.0
Depreciation, amortization, and accretion	55.7	55.8
Other	1.7	(1.0)
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, net	170.8	383.0
Prepaid expenses and other assets	(11.7)	(3.5)
Accounts payable	(31.2)	(18.4)
Accrued compensation	(14.1)	(47.2)
Income taxes payable	(7.6)	4.1
Other accrued liabilities	(51.1)	(8.9)
Deferred revenue	53.8	11.9
Net cash provided by operating activities	271.1	546.6
Cash flows from investing activities:
Purchases of property and equipment	(42.2)	(32.1)
Purchases of available-for-sale debt investments	(8.1)	(378.9)
Purchases of available-for-sale debt investments	968.0	218.8
Proceeds from maturities and redemptions of available-for-sale debt investments	215.4	184.3
Purchases of trading investments	0.0	(1.8)
Purchases of equity investments	(2.0)	0.0
Proceeds from sales of equity investments	3.3	0.0
Payment of escrow balance related to prior year acquisition	(22.2)	0.0
Net cash provided by (used in) investing activities	1,112.2	(9.7)
Cash flows from financing activities:
Repurchase and retirement of common stock, including prepayment under an accelerated share repurchase program	(754.2)	(129.7)
Proceeds from issuance of common stock	29.3	33.7
Payment of dividends	(62.1)	(38.0)
Change in customer financing arrangement	(16.6)	0.0
Net cash used in financing activities	(803.6)	(134.0)
Effect of foreign currency exchange rates on cash, cash equivalents and restricted cash	6.2	7.2
Net increase in cash, cash equivalents and restricted cash	585.9	410.1
Cash, cash equivalents and restricted cash at beginning of period	2,059.1	1,880.6
Cash, cash equivalents and restricted cash at end of period	$ 2,645.0	$ 2,290.7

Basis of Presentation	3 Months Ended
Basis of Presentation	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Basis of Presentation The unaudited Condensed Consolidated Financial Statements of Juniper Networks, Inc. (the “Company” or “Juniper”) have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The Condensed Consolidated Balance Sheet as of December 31, 2017, has been derived from the audited Consolidated Financial Statements at that date. In the opinion of management, all adjustments, including normal recurring accruals, considered necessary for a fair presentation have been included. The results of operations for the three months ended March 31, 2018, are not necessarily indicative of the results that may be expected for the year ending December 31, 2018, or any future period. The information included in this Quarterly Report on Form 10-Q (“Report”) should be read in conjunction with “Management's Discussion and Analysis of Financial Condition and Results of Operations,” “Risk Factors,” “Quantitative and Qualitative Disclosures About Market Risk,” and the Consolidated Financial Statements and footnotes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 (the "Form 10-K"). The Company adopted Financial Accounting Standards Board ("FASB") Accounting Standards Update ("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 $48.7 million in the prior period have been included with cash and cash equivalents when reconciling the beginning and ending total amounts, respectively, on the statement of cash flows for the three months ended March 31, 2017, 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 Condensed Consolidated Statement of Cash Flows for the three months ended March 31, 2017. See Note 3, Cash Equivalents and Investments for a reconciliation of the cash balances within our Condensed Consolidated Statements of Cash Flows to the Condensed Consolidated Balance Sheets. The preparation of the financial statements and related disclosures in accordance with U.S. GAAP requires the Company to make judgments, assumptions, and estimates that affect the amounts reported in the Condensed Consolidated Financial Statements and the accompanying notes. Actual results could differ materially from those estimates under different assumptions or conditions.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Except for the change in certain policies upon adoption of the accounting standards described below, there have been no material changes to the Company's significant accounting policies, compared to the accounting policies described in Note 2, Significant Accounting Policies, in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K.

Recently Adopted Accounting Standard

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 income (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 impact of the adoption on the Company's Condensed Consolidated Financial Statements was as follows:


•	Equity investments with readily determinable fair value: The Company is required to account for changes in fair value of its equity investments with readily determinable fair value in the statements of operations. The Company adopted the standard using a modified retrospective transition method, resulting in no impact to the January 1, 2018 opening accumulated deficit balance.

•

Equity investments without readily determinable fair value: The Company elected the measurement alternative, defined as cost, less impairments, adjusted for subsequent observable price changes on a prospective basis for all equity investments without readily determinable fair value and is required to account for any subsequent observable changes in fair value in the statements of operations. In addition, the Company is required to perform a qualitative assessment considering impairment indicators at each reporting period to evaluate whether the investment is impaired. If the investment is impaired, the Company will estimate the fair value of the investment and record an impairment loss in the statements of operations equal to the difference between the estimated fair value of the investment and its carrying amount. See Note 3, Cash Equivalents and Investments for additional disclosures required upon adopting the standard.

•

Deferred tax assets: The Company is required to assess the realizability of deferred tax assets related to available for sale debt securities in combination with its other deferred tax assets, using the same sources of taxable income that are used to assess the need for a valuation allowance on other deferred tax assets. The Company adopted the standard using a modified retrospective transition method, resulting in no impact to the January 1, 2018 opening accumulated deficit balance.

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 our Condensed 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		$	(211.7	)	$	818.6
Other accrued liabilities	304.3			31.3			335.6
Long-term deferred revenue	509.0			(124.6		)	384.4
Total liabilities	$	5,152.9		$	(305.0	)	$	4,847.9

Equity:
Accumulated deficit	$	(3,355.8	)	$	313.5		$	(3,042.3	)

Upon adoption, the Company recorded a cumulative effect adjustment of $313.5 million, net of tax adjustment of $61.4 million, which decreased the January 1, 2018 opening accumulated deficit balance on the Condensed 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 ("VSOE") 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 adoption of Topic 606 on the Company's Condensed Consolidated Statement of Operations and Condensed Consolidated Balance Sheet was as follows (in millions):



	Three Months Ended March 31, 2018^*
	As reported		Without Adoption of Topic 606		Topic 606 Impact
Net revenues:
Product	$	710.8	$	682.1	$	28.7
Service	371.8		398.6		(26.8		)
Total net revenues	$	1,082.6	$	1,080.7	$	1.9

________________________________


^*	Except as disclosed above, the adoption of Topic 606 did not have a significant impact on the Company’s Condensed Consolidated Statement of Operations for the three months ended March 31, 2018.



	As of March 31, 2018
	As reported			Without Adoption of Topic 606			Topic 606 Impact
Assets:
Accounts receivable, net of allowances	$	679.9		$	674.6		$	5.3
Prepaid expenses and other current assets	308.9			280.4			28.5
Other long-term assets	407.5			402.2			5.3
Total assets	$	9,078.5		$	9,039.4		$	39.1

Liabilities:
Deferred revenue	$	888.2		$	1,104.5		$	(216.3	)
Other accrued liabilities	230.5			170.6			59.9
Long-term deferred revenue	368.7			484.5			(115.8		)
Total liabilities	$	4,753.8		$	5,026.0		$	(272.2	)

Equity:
Accumulated deficit	$	(3,303.3	)	$	(3,614.6	)	$	311.3

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 Condensed Consolidated Statements of Operations.

Recent Accounting Standards Not Yet Effective

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, which expands an entity's ability to hedge financial and nonfinancial risk components and amends how companies assess effectiveness as well as changes the presentation and disclosure requirements. The new standard is to be applied on a modified retrospective basis and is effective for interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the impact of adoption on the Consolidated Financial Statements.

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 Company is currently evaluating the impact of adoption 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 Impairment, 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.

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. This pronouncement is effective for reporting periods beginning after December 15, 2019, and interim periods within those fiscal years, using a modified retrospective adoption method. Early adoption is permitted. The Company is currently evaluating the impact that this standard will have on its Consolidated Financial Statements and disclosures.

Leases: In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases, which requires recognition of lease assets and lease liabilities on the balance sheet by lessees for leases classified as operating leases with a lease term of more than twelve months. This ASU should be applied on a modified retrospective basis and is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company has commenced the assessment phase to determine the approach for implementing this standard and expects it to have a material impact on its Consolidated Balance Sheets and disclosures. The Company is still evaluating the impact this standard will have on the Consolidated Statements of Operations.

Cash Equivalents and Investments

3 Months Ended

Mar. 31, 2018

Cash Equivalents and Investments [Abstract]

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 March 31, 2018 and December 31, 2017 (in millions):



	As of March 31, 2018									As of December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Fixed income securities:
Asset-backed securities	$	118.6	$	—	$	(0.7	)	$	117.9	$	287.1	$	—	$	(0.6	)	$	286.5
Certificates of deposit	16.5		—		—			16.5		83.8		—		—			83.8
Commercial paper	40.2		—		—			40.2		217.1		—		—			217.1
Corporate debt securities	464.9		—		(5.1		)	459.8		929.6		0.4		(3.0		)	927.0
Foreign government debt securities	24.5		—		(0.2		)	24.3		62.9		—		(0.2		)	62.7
Time deposits	265.6		—		—			265.6		239.2		—		—			239.2
U.S. government agency securities	56.7		—		(0.5		)	56.2		143.9		—		(0.7		)	143.2
U.S. government securities	140.8		—		(0.9		)	139.9		406.8		0.1		(0.9		)	406.0
Total fixed income securities	1,127.8		—		(7.4		)	1,120.4		2,370.4		0.5		(5.4		)	2,365.5
Privately-held debt and redeemable preferred stock securities	16.1		37.4		—			53.5		15.9		37.4		—			53.3
Total available-for-sale debt securities	$	1,143.9	$	37.4	$	(7.4	)	$	1,173.9	$	2,386.3	$	37.9	$	(5.4	)	$	2,418.8

Reported as:
Cash equivalents	$	286.2	$	—	$	—		$	286.2	$	351.0	$	—	$	—		$	351.0
Short-term investments	318.9		—		(1.2		)	317.7		1,027.2		0.1		(1.2		)	1,026.1
Long-term investments	522.7		—		(6.2		)	516.5		992.2		0.4		(4.2		)	988.4
Other long-term assets	16.1		37.4		—			53.5		15.9		37.4		—			53.3
Total	$	1,143.9	$	37.4	$	(7.4	)	$	1,173.9	$	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 March 31, 2018 (in millions):



	Amortized Cost		Estimated Fair Value
Due in less than one year	$	605.1	$	603.9
Due between one and five years	522.7		516.5
Total	$	1,127.8	$	1,120.4

The following tables present the Company's total fixed income securities that were in an unrealized loss position as of March 31, 2018 and December 31, 2017 (in millions):



	As of March 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	$	90.7	$	(0.5	)	$	26.2	$	(0.2	)	$	116.9	$	(0.7	)
Corporate debt securities	359.4		(4.0		)	87.8		(1.1		)	447.2		(5.1		)
Foreign government debt securities	18.8		(0.2		)	5.5		—			24.3		(0.2		)
U.S. government agency securities	21.9		(0.1		)	34.3		(0.3		)	56.2		(0.4		)
U.S. government securities	97.0		(0.6		)	32.8		(0.4		)	129.8		(1.0		)
Total fixed income securities	$	587.8	$	(5.4	)	$	186.6	$	(2.0	)	$	774.4	$	(7.4	)



	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	)

For available-for-sale debt securities that have unrealized losses, the Company assesses impairment by evaluating various factors, including whether (i) it has the intention to sell any of these investments and (ii) whether it is more likely than not that it will be required to sell any of these investments before recovery of the entire amortized cost basis. As of March 31, 2018, the Company had 583 investments in unrealized loss positions. The gross unrealized losses related to these investments were primarily due to changes in market interest rates. The Company anticipates that it will recover the entire amortized cost basis of such available-for-sale debt securities and has determined that no other-than-temporary impairments associated with credit losses were required to be recognized during the three months ended March 31, 2018 and March 31, 2017.

During the three months ended March 31, 2018 and March 31, 2017, 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 March 31, 2018. Balances as of December 31, 2017 were included for comparative purpose and continue to be reported under the accounting standard in effect before adoption of ASU 2016-01 (in millions):



	As of
	March 31, 2018		December 31, 2017
Equity investments with readily determinable fair value
Money market funds ⁽¹⁾	$	1,584.1	$	969.8
Mutual funds ⁽²⁾	25.9		27.6
Equity investments without readily determinable fair value ⁽³⁾	30.4		29.7
Total equity securities	$	1,640.4	$	1,027.1

Reported as:
Cash equivalents	$	1,542.3	$	928.0
Prepaid expenses and other current assets	34.6		36.3
Other long-term assets	63.5		62.8
Total	$	1,640.4	$	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 Condensed Consolidated Statements of Operations.


⁽²⁾	Prior to January 1, 2018, mutual funds related to the Company's non-qualified deferred compensation ("NQDC") plan, were classified as trading securities. Unrealized gains or losses were recognized in the Condensed 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 Condensed Consolidated Statements of Operations.

For the three months ended March 31, 2018 and March 31, 2017, there were no material unrealized gains or losses recognized for equity investments.

Restricted Cash and Investments

There have been no material changes to the composition of the Company's restricted cash and investments as described in Note 4, Cash Equivalents and Investments, in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K, except that the restricted investments are now designated as equity investments upon adoption of ASU 2016-01 as described in Note 2, Summary of Significant Accounting Policies. As of March 31, 2018, total restricted cash and investments was $98.5 million, of which $62.4 million was included in prepaid expenses and other current assets and $36.1 million was included in other long-term assets on the Condensed Consolidated Balance Sheets.

The following table provides a reconciliation of cash, cash equivalents and restricted cash included in the Condensed Consolidated Balance Sheets as of March 31, 2018 and December 31, 2017 (in millions):



	As of
	March 31, 2018		December 31, 2017
Cash and cash equivalents	$	2,614.2	$	2,006.5
Restricted cash included in Prepaid expenses and other current assets	27.8		49.6
Restricted cash included in Other long-term assets	3.0		3.0
Total cash, cash equivalents and restricted cash	$	2,645.0	$	2,059.1

Fair Value Measurements

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following table provides a summary of assets and liabilities measured at fair value on a recurring basis and as reported in the Condensed Consolidated Balance Sheets (in millions):



	Fair Value Measurements at March 31, 2018										Fair Value Measurements at December 31, 2017
	Quoted Prices in Active Markets For Identical Assets (Level 1)		Significant Other Observable Remaining Inputs (Level 2)			Significant Other Unobservable Remaining Inputs (Level 3)		Total			Quoted Prices in Active Markets For Identical Assets (Level 1)		Significant Other Observable Remaining Inputs (Level 2)			Significant Other Unobservable Remaining Inputs (Level 3)		Total
Assets:
Available-for-sale debt securities:
Asset-backed securities	$	—	$	117.9		$	—	$	117.9		$	—	$	286.5		$	—	$	286.5
Certificates of deposit	—		16.5			—		16.5			—		83.8			—		83.8
Commercial paper	—		40.2			—		40.2			—		217.1			—		217.1
Corporate debt securities	—		459.8			—		459.8			—		927.0			—		927.0
Foreign government debt securities	—		24.3			—		24.3			—		62.7			—		62.7
Time deposits	—		265.6			—		265.6			—		239.2			—		239.2
U.S. government agency securities	—		56.2			—		56.2			—		143.2			—		143.2
U.S. government securities	122.9		17.0			—		139.9			322.4		83.6			—		406.0
Privately-held debt and redeemable preferred stock securities	—		—			53.5		53.5			—		—			53.3		53.3
Total available-for-sale debt securities	122.9		997.5			53.5		1,173.9			322.4		2,043.1			53.3		2,418.8
Equity securities:
Mutual funds⁽¹⁾	25.9		—			—		25.9			27.6		—			—		27.6
Money market funds⁽²⁾	1,584.1		—			—		1,584.1			969.8		—			—		969.8
Total equity securities	1,610.0		—			—		1,610.0			997.4		—			—		997.4
Derivative assets:
Foreign exchange contracts	—		15.9			—		15.9			—		9.2			—		9.2
Total assets measured at fair value	$	1,732.9	$	1,013.4		$	53.5	$	2,799.8		$	1,319.8	$	2,052.3		$	53.3	$	3,425.4
Liabilities:
Derivative liabilities:
Foreign exchange contracts	$	—	$	(0.7	)	$	—	$	(0.7	)	$	—	$	(1.8	)	$	—	$	(1.8	)
Total liabilities measured at fair value	$	—	$	(0.7	)	$	—	$	(0.7	)	$	—	$	(1.8	)	$	—	$	(1.8	)

Total assets, reported as:
Cash equivalents	$	1,542.3	$	286.2		$	—	$	1,828.5		$	928.1	$	350.9		$	—	$	1,279.0
Short-term investments	77.1		240.6			—		317.7			247.5		778.6			—		1,026.1
Long-term investments	45.8		470.7			—		516.5			74.8		913.6			—		988.4
Prepaid expenses and other current assets	34.6		15.9			—		50.5			36.3		9.2			—		45.5
Other long-term assets	33.1		—			53.5		86.6			33.1		—			53.3		86.4
Total assets measured at fair value	$	1,732.9	$	1,013.4		$	53.5	$	2,799.8		$	1,319.8	$	2,052.3		$	53.3	$	3,425.4

Total liabilities, reported as:
Other accrued liabilities	$	—	$	(0.7	)	$	—	$	(0.7	)	$	—	$	(1.8	)	$	—	$	(1.8	)
Total liabilities measured at fair value	$	—	$	(0.7	)	$	—	$	(0.7	)	$	—	$	(1.8	)	$	—	$	(1.8	)

________________________________


⁽¹⁾	Balance relates to restricted investments measured at fair value related to the Company's NQDC plan.


⁽²⁾	Balance includes $41.8 million restricted investments measured at fair value, related to the Company's Directors and Officers indemnification trust ("D&O") Trust and acquisition-related escrows as of March 31, 2018 and December 31, 2017.

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 three months ended March 31, 2018, the Company had no transfers between levels of the fair value hierarchy of its assets or liabilities measured at fair value.

All of the Company's privately-held debt and redeemable preferred stock securities are classified as Level 3 assets due to the lack of observable inputs to determine fair value. The Company estimates the fair value of its privately-held debt and redeemable preferred stock securities on a recurring basis using an analysis of the financial condition and near-term prospects of the investee, including recent financing activities and the investee's capital structure. During the three months ended March 31, 2018, there were no significant activities related to privately-held debt and redeemable preferred stocks securities.

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 three months ended March 31, 2018.

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 three months ended March 31, 2018, there was no impairment charges or adjustments resulting from observable price changes for equity investments without readily determinable fair value.

As of March 31, 2018 and December 31, 2017, the Company had no liabilities required to be measured at fair value on a nonrecurring basis.

Assets and Liabilities Not Measured at Fair Value

The carrying amounts of the Company's accounts receivable, accounts payable, and other accrued liabilities approximate fair value due to their short maturities. As of March 31, 2018 and December 31, 2017, the estimated fair value of the Company's short-term and long-term debt in the Condensed Consolidated Balance Sheets was $2,200.0 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”), of $61.2 million approximates its fair value as of March 31, 2018 and December 31, 2017. The Pulse Note is classified as a Level 3 asset due to the lack of observable inputs to determine fair value.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Derivative Instruments

3 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Instruments

The Company uses derivatives to partially offset its market exposure to fluctuations in certain foreign currencies and does not enter into derivatives for speculative or trading purposes.

The notional amount of the Company's foreign currency derivatives are summarized as follows (in millions):



	As of
	March 31, 2018		December 31, 2017
Cash flow hedges	$	378.3	$	521.1
Non-designated derivatives	157.7		108.3
Total	$	536.0	$	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. Execution of cash flow hedge derivatives typically occurs every month with maturities of eighteen months or less. As of March 31, 2018, an estimated $15.9 million of existing net gains within accumulated other comprehensive income (loss) is expected to be reclassified into earnings within the next 12 months.

The Company recognized an unrealized gain of $13.4 million and $7.0 million in accumulated other comprehensive income (loss) for the effective portion of its derivative instruments for the three months ended March 31, 2018 and March 31, 2017, respectively. The Company reclassified a gain of $5.6 million out of accumulated other comprehensive income (loss) to cost of revenues and operating expenses in the Condensed Consolidated Statements of Operations during the three months ended March 31, 2018. The amount reclassified out of accumulated other comprehensive income (loss) to cost of revenues and operating expenses in the Condensed Consolidated Statements of Operations during the three months ended March 31, 2017 was not material.

The ineffective portion of the Company's derivative instruments recognized in its Condensed Consolidated Statements of Operations was not material during the three months ended March 31, 2018 and March 31, 2017.

See Note 4, Fair Value Measurements, for the fair values of the Company's derivative instruments in the Condensed Consolidated Balance Sheets.

Non-Designated Derivatives

The Company also uses foreign currency forward contracts to mitigate variability in gains and losses generated from the remeasurement of certain monetary assets and liabilities denominated in foreign currencies. These foreign exchange forward contracts typically have maturities of approximately one 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 Condensed Consolidated Statements of Operations were not material during the three months ended March 31, 2018 and March 31, 2017.

Other Financial Information

3 Months Ended

Mar. 31, 2018

Other Financial Information [Abstract]

Other Financial Information

Inventory

Total inventory consisted of the following (in millions):



	As of
	March 31, 2018		December 31, 2017
Production and service materials	$	62.9	$	71.2
Finished goods	33.1		26.6
Inventory	$	96.0	$	97.8

Reported as:
Prepaid expenses and other current assets	$	92.6	$	93.8
Other long-term assets	3.4		4.0
Total	$	96.0	$	97.8

Warranties

Changes during the three months ended March 31, 2018 in the Company’s warranty reserve as reported within other accrued liabilities in the Condensed Consolidated Balance Sheets were as follows (in millions):



Balance as of December 31, 2017	$	27.4
Provisions made during the period	8.2
Actual costs incurred during the period	(8.3		)
Balance as of March 31, 2018	$	27.3

Deferred Revenue

Details of the Company's deferred revenue, as reported in the Condensed Consolidated Balance Sheets, were as follows (in millions):



	As of
	March 31, 2018			December 31, 2017
Deferred product revenue:
Undelivered product commitments and other product deferrals	$	166.4		$	312.6
Distributor inventory and other sell-through items	—			68.1
Deferred gross product revenue	166.4			380.7
Deferred cost of product revenue	(7.6		)	(46.5		)
Deferred product revenue, net	158.8			334.2
Deferred service revenue	1,098.1			1,205.1
Total	$	1,256.9		$	1,539.3
Reported as:
Current	$	888.2		$	1,030.3
Long-term	368.7			509.0
Total	$	1,256.9		$	1,539.3

Revenue

See Note 11, Segments for disaggregated revenue by product and service, customer vertical and geographic region.

Product and service revenue of $39.5 million and $265.0 million included in deferred revenue at January 1, 2018 was recognized during the three months ended March 31, 2018.

The following table summarizes the transaction price for contracts that have not yet been recognized as revenue as of March 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	$	166.4	$	144.0	$	19.1	$	3.3
Service	1,098.1		751.9		324.2		22.0
Total	$	1,264.5	$	895.9	$	343.3	$	25.3

Deferred Commissions

Deferred commissions were $30.9 million as of March 31, 2018. For the three months ended March 31, 2018, amortization expense for the deferred commissions was $40.5 million and there was no impairment loss in relation to the deferred commissions.

Other Expense, Net

Other expense, net, consisted of the following (in millions):



	Three Months Ended March 31,
	2018			2017
Interest income	$	14.9		$	10.4
Interest expense	(26.0		)	(25.3		)
(Loss) gain on investments, net	(0.5		)	1.2
Other	(2.5		)	(2.0		)
Other expense, net	$	(14.1	)	$	(15.7	)

Restructuring (Benefits) Charges

3 Months Ended

Mar. 31, 2018

Restructuring and Related Activities [Abstract]

Restructuring (Benefits) Charges

During 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 (benefits) charges in the Condensed Consolidated Statements of Operations.

Restructuring liabilities are reported within other accrued liabilities in the Condensed Consolidated Balance Sheets. The following table provides a summary of changes in the restructuring liabilities (in millions):



	December 31, 2017		Benefits			Cash Payments			Other		March 31, 2018
Severance	$	17.7	$	(0.9	)	$	(14.2	)	$	0.1	$	2.7
Contract terminations and other	2.3		(1.0		)	(1.3		)	—		—
Total	$	20.0	$	(1.9	)	$	(15.5	)	$	0.1	$	2.7

The Company does not anticipate future charges under the 2017 Restructuring Plan and expects to pay the remaining restructuring liabilities in the second quarter of 2018, at which time, the Company would consider the 2017 Restructuring Plan to be substantially completed.

Financing Arrangements	3 Months Ended
Financing Arrangements	Mar. 31, 2018
Receivables [Abstract]
Financing Arrangements	Financing Arrangements The Company provides certain customers with access to extended financing arrangements that allow for longer payment terms than those typically provided by the Company by factoring accounts receivable to third-party financing providers (“financing providers”). The program does not and is not intended to affect the timing of the Company's revenue recognition. Under the financing arrangements, proceeds from the financing providers are due to the Company within 1 to 90 days from the sale of the receivable. In these transactions with the financing providers, the Company surrenders control over the transferred assets. Pursuant to the financing arrangements for the sale of receivables, the Company sold net receivables of $35.8 million and $25.4 million during the three months ended March 31, 2018 and March 31, 2017, respectively. The Company received cash proceeds from financing providers of $33.0 million and $23.1 million during the three months ended March 31, 2018 and March 31, 2017, respectively. As of March 31, 2018 and December 31, 2017, the amounts owed by the financing providers were $16.5 million and $13.7 million, respectively, which were recorded in accounts receivable in the Condensed Consolidated Balance Sheets.

Equity

3 Months Ended

Mar. 31, 2018

Stockholders' Equity Note [Abstract]

Equity

Cash Dividends on Shares of Common Stock

During the three months ended March 31, 2018, the Company declared a quarterly cash dividend of $0.18 per share of common stock on January 30, 2018, which was paid on March 22, 2018 to stockholders of record on March 1, 2018 in the aggregate amount of $62.1 million. 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 15, Subsequent Events, for discussion of the Company's dividend declaration subsequent to March 31, 2018.

Stock Repurchase Activities

In January 2018, the Board approved a $2.0 billion share repurchase program, including $750.0 million to be used pursuant to an accelerated share repurchase program ("2018 Stock 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 three months ended March 31, 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 for an aggregate price of $600.0 million, based on the market value of the Company's common stock on the date of the transaction. The initial shares received by the Company were retired, accounted for as a reduction to stockholders' equity in the Condensed Consolidated Balance Sheets, and treated as a repurchase of common stock for purposes of calculating earnings per share. The forward contract for the remaining $150.0 million is considered indexed to the Company's common stock and met all of the applicable criteria for equity classification.

The total number of shares of the Company's common stock to be ultimately received under the ASR will be calculated using the average daily volume weighted average price of the Company's stock during the repurchase period, less an agreed upon discount. Final settlement of the transactions under the ASR is expected to be completed no sooner than May 11, 2018 and no later than August 6, 2018. If the initial shares received are less than the calculated total number of shares to be ultimately received under the ASR, then the financial institutions will be required to deliver additional shares of common stock to the Company at settlement. If however, the initial shares received are greater than the calculated total number of shares to be ultimately received, the Company has the option to either issue shares of common stock or make cash payments to the financial institutions.

The following table summarizes the Company's stock repurchases and retirements, including prepayment pursuant to the ASR, under its stock repurchase programs (in millions, except per share amounts):



	Three Months Ended March 31,
	2018 ⁽¹⁾		2017 ⁽²⁾
Repurchases Under Stock Repurchase Program
Shares repurchased	23.3		4.5
Average price per share	$	25.80	$	28.03
Amount repurchased	$	750.0	$	125.0

________________________________

⁽¹⁾Shares repurchased under the 2018 Stock Repurchase Program.

⁽²⁾Shares repurchased under the 2014 Stock Repurchase Program.

As of March 31, 2018, there was $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.

In addition to repurchases under the 2018 Stock Repurchase Program, the Company also repurchases common stock from certain employees in connection with the net issuance of shares to satisfy applicable tax withholding requirements upon the vesting of certain stock awards issued to such employees. Repurchases associated with tax withholdings were not material during the three months ended March 31, 2018 and March 31, 2017.

Accumulated Other Comprehensive Income (Loss), Net of Tax

The components of accumulated other comprehensive income (loss), net of related taxes, for the three months ended March 31, 2018 were as follows (in millions):



	Unrealized Gains/Losses on Available-for- Sale Debt Securities⁽¹⁾			Unrealized Gains on Cash Flow Hedges⁽²⁾			Foreign Currency Translation Adjustments			Total
Balance as of December 31, 2017	$	19.0		$	6.0		$	(30.4	)	$	(5.4	)
Other comprehensive income before reclassifications	(2.0		)	13.1			5.3			16.4
Amount reclassified from accumulated other comprehensive income (loss)	0.9			(5.1		)	—			(4.2		)
Reclassification of tax effects upon adoption of ASU 2018-02	5.0			0.7			—			5.7
Other comprehensive income, net	3.9			8.7			5.3			17.9
Balance as of March 31, 2018	$	22.9		$	14.7		$	(25.1	)	$	12.5

________________________________


⁽¹⁾	The reclassifications out of accumulated other comprehensive income (loss) during the three months ended March 31, 2018 for realized losses on available-for-sale debt securities were included in other expense, net, in the Condensed Consolidated Statements of Operations.


⁽²⁾	The reclassifications out of accumulated other comprehensive income (loss) during the three months ended March 31, 2018 for realized gains on cash flow hedges were included within cost of revenues, research and development, sales and marketing, and general and administrative in the Condensed Consolidated Statements of Operations and were not material individually.

Employee Benefit Plans

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Employee Benefit Plans

Equity Incentive Plans

The Company has stock-based compensation plans pursuant to which it has granted stock options, restricted stock units (“RSUs”), and performance share awards (“PSAs”). The Company also maintains its 2008 Employee Stock Purchase Plan (the “ESPP”) for all eligible employees.

As of March 31, 2018, 24.3 million and 9.9 million shares were available for future issuance under the Company's 2015 Equity Incentive Plan (the "2015 Plan") and the ESPP, respectively.

Stock Option Activities

The following table summarizes the Company’s stock option activity and related information as of and for the three months ended March 31, 2018 (in millions, except for per share amounts and years):



	Outstanding Options
	Number of Shares		Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term (In Years)	Aggregate Intrinsic Value
Balance as of December 31, 2017	0.9		$	34.41
Expired/Canceled	(0.6	)	40.75
Balance as of March 31, 2018	0.3		$	20.02	2.5	$	1.9

As of March 31, 2018:
Vested and expected-to-vest options	0.3		$	20.02	2.5	$	1.9
Exercisable options	0.2		$	21.87	1.8	$	1.4

Restricted Stock Unit, Restricted Stock Award, and Performance Share Award Activities

The Company’s RSU, restricted stock award ("RSA"), and PSA activity and related information as of and for the three months ended March 31, 2018 were as follows (in millions, except per share amounts and years):



	Outstanding RSUs, RSAs, and PSAs⁽⁴⁾
	Number of Shares		Weighted Average Grant-Date Fair Value per Share		Weighted Average Remaining Contractual Term (In Years)	Aggregate Intrinsic Value
Balance as of December 31, 2017	19.5		$	25.39
RSUs granted ⁽¹⁾⁽³⁾	4.9		25.11
PSAs granted⁽²⁾⁽³⁾	0.7		24.43
RSUs vested	(4.5	)	25.42
PSAs vested	(1.1	)	24.13
RSUs canceled	(0.5	)	26.36
PSAs canceled	(0.6	)	24.26
Balance as of March 31, 2018	18.4		$	25.35	1.4	$	448.0

________________________________

⁽¹⁾

Includes service-based and market-based RSUs. The number of shares subject to market-based condition 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 market-based condition that would be issued if market criteria determined by the Compensation Committee of the Board are achieved at target is 0.1 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 0.3 million shares.

⁽²⁾

The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee of the Board are achieved at target is 0.4 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 0.7 million shares.

⁽³⁾

The grant date fair value of RSUs and PSAs were reduced by the present value of dividends expected to be paid on the underlying shares of common stock during the requisite and derived service period as these awards are not entitled to receive dividends until vested. During the three months ended March 31, 2018, the Company declared a quarterly cash dividend of $0.18 per share of common stock on January 30, 2018.

⁽⁴⁾

Excludes 1.9 million shares of PSAs that were modified during the three months ended March 31, 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 $5.6 million to be recognized over the remaining terms of the modified awards.

Employee Stock Purchase Plan

On November 6, 2017, the Company’s Compensation Committee amended and restated the ESPP to provide that for the offering period that begins on February 1, 2018, the ESPP will consist of a 24-month offering period with four 6-month purchase periods in each offering period. The purchase price for the Company’s common stock under the ESPP will be 85% of the lower of the fair market value of the shares at (1) the beginning of a rolling 2 year 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.

For the three months ended March 31, 2018 and March 31, 2017, employees purchased approximately 1.3 million and 1.5 million shares of common stock through the ESPP at an average exercise price of $22.23 and $19.21 per share, respectively.

Share-Based Compensation Expense

Share-based compensation expense associated with stock options, RSUs, RSAs, PSAs, and ESPP was recorded in the following cost and expense categories in the Condensed Consolidated Statements of Operations (in millions):



	Three Months Ended March 31,
	2018		2017
Cost of revenues - Product	$	1.9	$	0.9
Cost of revenues - Service	4.8		4.3
Research and development	44.1		34.8
Sales and marketing	13.5		15.3
General and administrative	6.1		6.7
Total	$	70.4	$	62.0

The following table summarizes share-based compensation expense by award type (in millions):



	Three Months Ended March 31,
	2018		2017
Stock options	$	0.1	$	0.1
RSUs, RSAs, and PSAs	65.6		57.8
ESPP	4.7		4.1
Total	$	70.4	$	62.0

As of March 31, 2018, the total unrecognized compensation cost related to unvested share-based awards was $413.9 million to be recognized over a weighted-average period of 1.9 years.

Segments

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

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):



	Three Months Ended March 31,
	2018		2017
Routing	$	408.1	$	521.6
Switching	230.0		241.6
Security	72.7		65.7
Total product	710.8		828.9

Total service	371.8		392.1
Total	$	1,082.6	$	1,221.0

The following table presents net revenues by customer vertical (in millions):



	Three Months Ended March 31,
	2018		2017
Cloud	$	268.3	$	331.6
Service Provider	479.9		568.5
Enterprise	334.4		320.9
Total	$	1,082.6	$	1,221.0

The Company attributes revenues to geographic region based on the customer’s shipping address. The following table presents net revenues by geographic region (in millions):



	Three Months Ended March 31,
	2018		2017
Americas:
United States	$	532.3	$	658.1
Other	55.3		53.5
Total Americas	587.6		711.6
Europe, Middle East, and Africa	308.0		284.5
Asia Pacific	187.0		224.9
Total	$	1,082.6	$	1,221.0

Income Taxes

3 Months Ended

Mar. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

The following table provides details of income taxes (in millions, except percentages):



	Three Months Ended March 31,
	2018			2017
Income before income taxes	$	41.4		$	140.6
Income tax provision	$	7.0		$	31.8
Effective tax rate	16.9		%	22.6		%

The Tax Act enacted in December 22, 2017 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% and created a minimum tax on foreign earnings.

Due to the timing of the enactment and the complexity involved in applying the provisions of the Tax Act, the Company made reasonable estimates of the effects and recorded provisional amounts in the financial statements as of December 31, 2017. As the Company collects and prepares the necessary data, interprets the Tax Act and reviews any additional guidance issued by the U.S. Treasury Department, state revenue and taxation authorities and other standard-setting bodies, the Company may make adjustments to the provisional amounts which may materially impact its provision for income taxes from continuing operations in the period in which the adjustments are made. The adjustments made in the first quarter of 2018 were not material. The accounting for the tax effects of the Tax Act will be completed later in 2018.

The Tax Act also includes provisions for Global Intangible Low-Taxed Income (“GILTI”), which imposes taxes on foreign income in excess of a deemed return on tangible assets of foreign corporations. Because of the complexities of the new provisions, the Company is continuing to evaluate how the provisions will be accounted for under U.S. GAAP. Companies are allowed to make an accounting policy election of either (i) account for GILTI as a component of income tax expense in the period in which the Company is subject to the rules (the “period cost method”), or (ii) account for GILTI in the Company’s measurement of deferred taxes (the “deferred method”). The Company has not elected a method and will do so after completing its analysis of the GILTI provisions of the Tax Act depending on the analysis of the Company’s global income. Therefore, the Company has not recorded any potential deferred tax effects related to the GILTI in its financial statements and has no policy election regarding whether to record deferred taxes on GILTI or use the period cost method. The Company has however, included an estimate of the current GILTI impact in its annual effective tax rate for 2018. The Company expects to complete the accounting during the measurement period.

The Company's effective tax rate during the three months ended March 31, 2018 differs from the statutory rate of 21% primarily due to the benefit of the federal research and development credit and foreign earnings taxed at lower rates. The rate for the period includes a discrete benefit of 4.4% primarily related to the net impact of unrecognized tax benefits.

As of March 31, 2018, the total amount of gross unrecognized tax benefits was $263.1 million.

The Company engages in continuous discussions and negotiations with tax authorities regarding tax matters in various jurisdictions. It is reasonably possible that the balance of unrecognized tax benefits could decrease up to $45.8 million within the next twelve months due to lapses of applicable statutes of limitations and the completion of tax review cycles in various tax jurisdictions. The balance primarily relates to matters involving U.S and non-U.S taxation of cross-border transactions and the utilization of losses.

Net Income Per Share

3 Months Ended

Mar. 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):



	Three Months Ended March 31,
	2018		2017
Numerator:
Net income	$	34.4	$	108.8
Denominator:
Weighted-average shares used to compute basic net income per share	355.3		380.9
Dilutive effect of employee stock awards	5.3		7.1
Weighted-average shares used to compute diluted net income per share	360.6		388.0
Net income per share
Basic	$	0.10	$	0.29
Diluted	$	0.10	$	0.28

Anti-dilutive shares	10.4		1.6

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments Except for the items below, there have been no material changes to the Company's commitments compared to the commitments described in Note 16, Commitments and Contingencies, in Notes to Consolidated Financial Statements in Item 8 of Part II of the Form 10-K. 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 $616.6 million as of March 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 March 31, 2018, the Company had accrued $25.8 million based on its estimate of such charges. 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 March 31, 2018 and December 31, 2017, the Company recorded $9.4 million and $20.4 million, respectively, for such indemnification obligations in other accrued liabilities and other long-term liabilities on the Condensed Consolidated Balance Sheets. Legal Proceedings Investigations The Company previously disclosed that the U.S. Securities and Exchange Commission ("SEC") and the U.S. Department of Justice ("DOJ") were conducting investigations into possible violations by the Company of the U.S. Foreign Corrupt Practices Act ("FCPA"). The Company has been cooperating with these agencies regarding these matters. 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’s Audit Committee, with the assistance of independent advisors, has been investigating and conducting a thorough review of possible violations of the FCPA, and has made recommendations for remedial measures, including employee disciplinary actions in foreign jurisdictions, which the Company has implemented and continues to implement. The Company is unable to predict the duration, scope or outcome of the ongoing SEC investigation, but believes that an adverse outcome is reasonably possible. However, the Company is not able to estimate a reasonable range of possible loss. The SEC could take action against the Company or the Company could agree to settle. In such event, the Company could be required to pay substantial fines and sanctions and/or implement additional remedial measures; in addition, it may be determined that the Company violated the FCPA. Other Litigations and Investigations In addition to the investigations discussed above, the Company is involved in other investigations, disputes, litigations, and legal proceedings. The Company records an accrual for loss contingencies for legal proceedings when it believes that an unfavorable outcome is both (a) probable and (b) the amount or range of any possible loss is reasonably estimable. The Company intends to aggressively defend itself in these matters, and while there can be no assurances and the outcome of these matters is currently not determinable, the Company currently believes that none of these existing claims or proceedings are likely to have a material adverse effect on its financial position. Notwithstanding the foregoing, there are many uncertainties associated with any litigation and these matters or other third-party claims against the Company may cause the Company to incur costly litigation and/or substantial settlement charges. In addition, the resolution of any intellectual property litigation may require the Company to make royalty payments, which could adversely affect gross margins in future periods. If any of those events were to occur, the Company's business, financial condition, results of operations, and cash flows could be adversely affected. The actual liability in any such matters may be materially different from the Company's estimates, if any, which could result in the need to adjust the liability and record additional expenses.

Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Dividend Declaration On May 2, 2018, the Company announced that it had declared a cash dividend of $0.18 per share of common stock payable on June 22, 2018 to stockholders of record as of the close of business on June 1, 2018.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Basis of Presentation

The unaudited Condensed Consolidated Financial Statements of Juniper Networks, Inc. (the “Company” or “Juniper”) have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The Condensed Consolidated Balance Sheet as of December 31, 2017, has been derived from the audited Consolidated Financial Statements at that date. In the opinion of management, all adjustments, including normal recurring accruals, considered necessary for a fair presentation have been included. The results of operations for the three months ended March 31, 2018, are not necessarily indicative of the results that may be expected for the year ending December 31, 2018, or any future period.

The information included in this Quarterly Report on Form 10-Q (“Report”) should be read in conjunction with “Management's Discussion and Analysis of Financial Condition and Results of Operations,” “Risk Factors,” “Quantitative and Qualitative Disclosures About Market Risk,” and the Consolidated Financial Statements and footnotes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 (the "Form 10-K").

The Company adopted Financial Accounting Standards Board ("FASB") Accounting Standards Update ("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 $48.7 million in the prior period have been included with cash and cash equivalents when reconciling the beginning and ending total amounts, respectively, on the statement of cash flows for the three months ended March 31, 2017, 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 Condensed Consolidated Statement of Cash Flows for the three months ended March 31, 2017. See Note 3, Cash Equivalents and Investments for a reconciliation of the cash balances within our Condensed Consolidated Statements of Cash Flows to the Condensed Consolidated Balance Sheets.

The preparation of the financial statements and related disclosures in accordance with U.S. GAAP requires the Company to make judgments, assumptions, and estimates that affect the amounts reported in the Condensed Consolidated Financial Statements and the accompanying notes. Actual results could differ materially from those estimates under different assumptions or conditions.

Recent accounting pronouncements

Recently Adopted Accounting Standard

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 income (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 impact of the adoption on the Company's Condensed Consolidated Financial Statements was as follows:


•	Equity investments with readily determinable fair value: The Company is required to account for changes in fair value of its equity investments with readily determinable fair value in the statements of operations. The Company adopted the standard using a modified retrospective transition method, resulting in no impact to the January 1, 2018 opening accumulated deficit balance.

•

Equity investments without readily determinable fair value: The Company elected the measurement alternative, defined as cost, less impairments, adjusted for subsequent observable price changes on a prospective basis for all equity investments without readily determinable fair value and is required to account for any subsequent observable changes in fair value in the statements of operations. In addition, the Company is required to perform a qualitative assessment considering impairment indicators at each reporting period to evaluate whether the investment is impaired. If the investment is impaired, the Company will estimate the fair value of the investment and record an impairment loss in the statements of operations equal to the difference between the estimated fair value of the investment and its carrying amount. See Note 3, Cash Equivalents and Investments for additional disclosures required upon adopting the standard.

•

Deferred tax assets: The Company is required to assess the realizability of deferred tax assets related to available for sale debt securities in combination with its other deferred tax assets, using the same sources of taxable income that are used to assess the need for a valuation allowance on other deferred tax assets. The Company adopted the standard using a modified retrospective transition method, resulting in no impact to the January 1, 2018 opening accumulated deficit balance.

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 our Condensed 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		$	(211.7	)	$	818.6
Other accrued liabilities	304.3			31.3			335.6
Long-term deferred revenue	509.0			(124.6		)	384.4
Total liabilities	$	5,152.9		$	(305.0	)	$	4,847.9

Equity:
Accumulated deficit	$	(3,355.8	)	$	313.5		$	(3,042.3	)

Upon adoption, the Company recorded a cumulative effect adjustment of $313.5 million, net of tax adjustment of $61.4 million, which decreased the January 1, 2018 opening accumulated deficit balance on the Condensed 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 ("VSOE") 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 adoption of Topic 606 on the Company's Condensed Consolidated Statement of Operations and Condensed Consolidated Balance Sheet was as follows (in millions):



	Three Months Ended March 31, 2018^*
	As reported		Without Adoption of Topic 606		Topic 606 Impact
Net revenues:
Product	$	710.8	$	682.1	$	28.7
Service	371.8		398.6		(26.8		)
Total net revenues	$	1,082.6	$	1,080.7	$	1.9

________________________________


^*	Except as disclosed above, the adoption of Topic 606 did not have a significant impact on the Company’s Condensed Consolidated Statement of Operations for the three months ended March 31, 2018.



	As of March 31, 2018
	As reported			Without Adoption of Topic 606			Topic 606 Impact
Assets:
Accounts receivable, net of allowances	$	679.9		$	674.6		$	5.3
Prepaid expenses and other current assets	308.9			280.4			28.5
Other long-term assets	407.5			402.2			5.3
Total assets	$	9,078.5		$	9,039.4		$	39.1

Liabilities:
Deferred revenue	$	888.2		$	1,104.5		$	(216.3	)
Other accrued liabilities	230.5			170.6			59.9
Long-term deferred revenue	368.7			484.5			(115.8		)
Total liabilities	$	4,753.8		$	5,026.0		$	(272.2	)

Equity:
Accumulated deficit	$	(3,303.3	)	$	(3,614.6	)	$	311.3

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 Condensed Consolidated Statements of Operations.

Recent Accounting Standards Not Yet Effective

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, which expands an entity's ability to hedge financial and nonfinancial risk components and amends how companies assess effectiveness as well as changes the presentation and disclosure requirements. The new standard is to be applied on a modified retrospective basis and is effective for interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the impact of adoption on the Consolidated Financial Statements.

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 Company is currently evaluating the impact of adoption 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 Impairment, 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.

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. This pronouncement is effective for reporting periods beginning after December 15, 2019, and interim periods within those fiscal years, using a modified retrospective adoption method. Early adoption is permitted. The Company is currently evaluating the impact that this standard will have on its Consolidated Financial Statements and disclosures.

Leases: In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases, which requires recognition of lease assets and lease liabilities on the balance sheet by lessees for leases classified as operating leases with a lease term of more than twelve months. This ASU should be applied on a modified retrospective basis and is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted. The Company has commenced the assessment phase to determine the approach for implementing this standard and expects it to have a material impact on its Consolidated Balance Sheets and disclosures. The Company is still evaluating the impact this standard will have on the Consolidated Statements of Operations.

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2018

Accounting Policies [Abstract]

Schedule of new accounting pronouncements and changes in accounting principles

The cumulative effect of the changes made to our Condensed 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		$	(211.7	)	$	818.6
Other accrued liabilities	304.3			31.3			335.6
Long-term deferred revenue	509.0			(124.6		)	384.4
Total liabilities	$	5,152.9		$	(305.0	)	$	4,847.9

Equity:
Accumulated deficit	$	(3,355.8	)	$	313.5		$	(3,042.3	)

The impact of adoption of Topic 606 on the Company's Condensed Consolidated Statement of Operations and Condensed Consolidated Balance Sheet was as follows (in millions):



	Three Months Ended March 31, 2018^*
	As reported		Without Adoption of Topic 606		Topic 606 Impact
Net revenues:
Product	$	710.8	$	682.1	$	28.7
Service	371.8		398.6		(26.8		)
Total net revenues	$	1,082.6	$	1,080.7	$	1.9

________________________________


^*	Except as disclosed above, the adoption of Topic 606 did not have a significant impact on the Company’s Condensed Consolidated Statement of Operations for the three months ended March 31, 2018.



	As of March 31, 2018
	As reported			Without Adoption of Topic 606			Topic 606 Impact
Assets:
Accounts receivable, net of allowances	$	679.9		$	674.6		$	5.3
Prepaid expenses and other current assets	308.9			280.4			28.5
Other long-term assets	407.5			402.2			5.3
Total assets	$	9,078.5		$	9,039.4		$	39.1

Liabilities:
Deferred revenue	$	888.2		$	1,104.5		$	(216.3	)
Other accrued liabilities	230.5			170.6			59.9
Long-term deferred revenue	368.7			484.5			(115.8		)
Total liabilities	$	4,753.8		$	5,026.0		$	(272.2	)

Equity:
Accumulated deficit	$	(3,303.3	)	$	(3,614.6	)	$	311.3

Cash Equivalents and Investments (Tables)

3 Months Ended

Mar. 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 March 31, 2018 and December 31, 2017 (in millions):



	As of March 31, 2018									As of December 31, 2017
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Fixed income securities:
Asset-backed securities	$	118.6	$	—	$	(0.7	)	$	117.9	$	287.1	$	—	$	(0.6	)	$	286.5
Certificates of deposit	16.5		—		—			16.5		83.8		—		—			83.8
Commercial paper	40.2		—		—			40.2		217.1		—		—			217.1
Corporate debt securities	464.9		—		(5.1		)	459.8		929.6		0.4		(3.0		)	927.0
Foreign government debt securities	24.5		—		(0.2		)	24.3		62.9		—		(0.2		)	62.7
Time deposits	265.6		—		—			265.6		239.2		—		—			239.2
U.S. government agency securities	56.7		—		(0.5		)	56.2		143.9		—		(0.7		)	143.2
U.S. government securities	140.8		—		(0.9		)	139.9		406.8		0.1		(0.9		)	406.0
Total fixed income securities	1,127.8		—		(7.4		)	1,120.4		2,370.4		0.5		(5.4		)	2,365.5
Privately-held debt and redeemable preferred stock securities	16.1		37.4		—			53.5		15.9		37.4		—			53.3
Total available-for-sale debt securities	$	1,143.9	$	37.4	$	(7.4	)	$	1,173.9	$	2,386.3	$	37.9	$	(5.4	)	$	2,418.8

Reported as:
Cash equivalents	$	286.2	$	—	$	—		$	286.2	$	351.0	$	—	$	—		$	351.0
Short-term investments	318.9		—		(1.2		)	317.7		1,027.2		0.1		(1.2		)	1,026.1
Long-term investments	522.7		—		(6.2		)	516.5		992.2		0.4		(4.2		)	988.4
Other long-term assets	16.1		37.4		—			53.5		15.9		37.4		—			53.3
Total	$	1,143.9	$	37.4	$	(7.4	)	$	1,173.9	$	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 March 31, 2018 (in millions):



	Amortized Cost		Estimated Fair Value
Due in less than one year	$	605.1	$	603.9
Due between one and five years	522.7		516.5
Total	$	1,127.8	$	1,120.4

Available-for-sale securities in unrealized loss position

The following tables present the Company's total fixed income securities that were in an unrealized loss position as of March 31, 2018 and December 31, 2017 (in millions):



	As of March 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	$	90.7	$	(0.5	)	$	26.2	$	(0.2	)	$	116.9	$	(0.7	)
Corporate debt securities	359.4		(4.0		)	87.8		(1.1		)	447.2		(5.1		)
Foreign government debt securities	18.8		(0.2		)	5.5		—			24.3		(0.2		)
U.S. government agency securities	21.9		(0.1		)	34.3		(0.3		)	56.2		(0.4		)
U.S. government securities	97.0		(0.6		)	32.8		(0.4		)	129.8		(1.0		)
Total fixed income securities	$	587.8	$	(5.4	)	$	186.6	$	(2.0	)	$	774.4	$	(7.4	)



	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 March 31, 2018. Balances as of December 31, 2017 were included for comparative purpose and continue to be reported under the accounting standard in effect before adoption of ASU 2016-01 (in millions):



	As of
	March 31, 2018		December 31, 2017
Equity investments with readily determinable fair value
Money market funds ⁽¹⁾	$	1,584.1	$	969.8
Mutual funds ⁽²⁾	25.9		27.6
Equity investments without readily determinable fair value ⁽³⁾	30.4		29.7
Total equity securities	$	1,640.4	$	1,027.1

Reported as:
Cash equivalents	$	1,542.3	$	928.0
Prepaid expenses and other current assets	34.6		36.3
Other long-term assets	63.5		62.8
Total	$	1,640.4	$	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 Condensed Consolidated Statements of Operations.


⁽²⁾	Prior to January 1, 2018, mutual funds related to the Company's non-qualified deferred compensation ("NQDC") plan, were classified as trading securities. Unrealized gains or losses were recognized in the Condensed 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 Condensed 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 Condensed Consolidated Balance Sheets as of March 31, 2018 and December 31, 2017 (in millions):



	As of
	March 31, 2018		December 31, 2017
Cash and cash equivalents	$	2,614.2	$	2,006.5
Restricted cash included in Prepaid expenses and other current assets	27.8		49.6
Restricted cash included in Other long-term assets	3.0		3.0
Total cash, cash equivalents and restricted cash	$	2,645.0	$	2,059.1

Fair Value Measurements (Tables)

3 Months Ended

Mar. 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 Condensed Consolidated Balance Sheets (in millions):



	Fair Value Measurements at March 31, 2018										Fair Value Measurements at December 31, 2017
	Quoted Prices in Active Markets For Identical Assets (Level 1)		Significant Other Observable Remaining Inputs (Level 2)			Significant Other Unobservable Remaining Inputs (Level 3)		Total			Quoted Prices in Active Markets For Identical Assets (Level 1)		Significant Other Observable Remaining Inputs (Level 2)			Significant Other Unobservable Remaining Inputs (Level 3)		Total
Assets:
Available-for-sale debt securities:
Asset-backed securities	$	—	$	117.9		$	—	$	117.9		$	—	$	286.5		$	—	$	286.5
Certificates of deposit	—		16.5			—		16.5			—		83.8			—		83.8
Commercial paper	—		40.2			—		40.2			—		217.1			—		217.1
Corporate debt securities	—		459.8			—		459.8			—		927.0			—		927.0
Foreign government debt securities	—		24.3			—		24.3			—		62.7			—		62.7
Time deposits	—		265.6			—		265.6			—		239.2			—		239.2
U.S. government agency securities	—		56.2			—		56.2			—		143.2			—		143.2
U.S. government securities	122.9		17.0			—		139.9			322.4		83.6			—		406.0
Privately-held debt and redeemable preferred stock securities	—		—			53.5		53.5			—		—			53.3		53.3
Total available-for-sale debt securities	122.9		997.5			53.5		1,173.9			322.4		2,043.1			53.3		2,418.8
Equity securities:
Mutual funds⁽¹⁾	25.9		—			—		25.9			27.6		—			—		27.6
Money market funds⁽²⁾	1,584.1		—			—		1,584.1			969.8		—			—		969.8
Total equity securities	1,610.0		—			—		1,610.0			997.4		—			—		997.4
Derivative assets:
Foreign exchange contracts	—		15.9			—		15.9			—		9.2			—		9.2
Total assets measured at fair value	$	1,732.9	$	1,013.4		$	53.5	$	2,799.8		$	1,319.8	$	2,052.3		$	53.3	$	3,425.4
Liabilities:
Derivative liabilities:
Foreign exchange contracts	$	—	$	(0.7	)	$	—	$	(0.7	)	$	—	$	(1.8	)	$	—	$	(1.8	)
Total liabilities measured at fair value	$	—	$	(0.7	)	$	—	$	(0.7	)	$	—	$	(1.8	)	$	—	$	(1.8	)

Total assets, reported as:
Cash equivalents	$	1,542.3	$	286.2		$	—	$	1,828.5		$	928.1	$	350.9		$	—	$	1,279.0
Short-term investments	77.1		240.6			—		317.7			247.5		778.6			—		1,026.1
Long-term investments	45.8		470.7			—		516.5			74.8		913.6			—		988.4
Prepaid expenses and other current assets	34.6		15.9			—		50.5			36.3		9.2			—		45.5
Other long-term assets	33.1		—			53.5		86.6			33.1		—			53.3		86.4
Total assets measured at fair value	$	1,732.9	$	1,013.4		$	53.5	$	2,799.8		$	1,319.8	$	2,052.3		$	53.3	$	3,425.4

Total liabilities, reported as:
Other accrued liabilities	$	—	$	(0.7	)	$	—	$	(0.7	)	$	—	$	(1.8	)	$	—	$	(1.8	)
Total liabilities measured at fair value	$	—	$	(0.7	)	$	—	$	(0.7	)	$	—	$	(1.8	)	$	—	$	(1.8	)

Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative instruments

The notional amount of the Company's foreign currency derivatives are summarized as follows (in millions):



	As of
	March 31, 2018		December 31, 2017
Cash flow hedges	$	378.3	$	521.1
Non-designated derivatives	157.7		108.3
Total	$	536.0	$	629.4

- Definition

Tabular disclosure of pertinent information about a derivative or group of derivatives on a disaggregated basis, such as for individual instruments, or small groups of similar instruments. May include a combination of the type of instrument, risks being hedged, notional amount, hedge designation, related hedged item, inception date, maturity date, or other relevant item.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41641-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41678-113959

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41638-113959

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579240-113959

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41620-113959

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(n)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

Other Financial Information (Tables)

3 Months Ended

Mar. 31, 2018

Other Financial Information [Abstract]

Inventories

Total inventory consisted of the following (in millions):



	As of
	March 31, 2018		December 31, 2017
Production and service materials	$	62.9	$	71.2
Finished goods	33.1		26.6
Inventory	$	96.0	$	97.8

Reported as:
Prepaid expenses and other current assets	$	92.6	$	93.8
Other long-term assets	3.4		4.0
Total	$	96.0	$	97.8

Warranties

Changes during the three months ended March 31, 2018 in the Company’s warranty reserve as reported within other accrued liabilities in the Condensed Consolidated Balance Sheets were as follows (in millions):



Balance as of December 31, 2017	$	27.4
Provisions made during the period	8.2
Actual costs incurred during the period	(8.3		)
Balance as of March 31, 2018	$	27.3

Deferred revenue

Details of the Company's deferred revenue, as reported in the Condensed Consolidated Balance Sheets, were as follows (in millions):



	As of
	March 31, 2018			December 31, 2017
Deferred product revenue:
Undelivered product commitments and other product deferrals	$	166.4		$	312.6
Distributor inventory and other sell-through items	—			68.1
Deferred gross product revenue	166.4			380.7
Deferred cost of product revenue	(7.6		)	(46.5		)
Deferred product revenue, net	158.8			334.2
Deferred service revenue	1,098.1			1,205.1
Total	$	1,256.9		$	1,539.3
Reported as:
Current	$	888.2		$	1,030.3
Long-term	368.7			509.0
Total	$	1,256.9		$	1,539.3

Other expense, net

Other expense, net, consisted of the following (in millions):



	Three Months Ended March 31,
	2018			2017
Interest income	$	14.9		$	10.4
Interest expense	(26.0		)	(25.3		)
(Loss) gain on investments, net	(0.5		)	1.2
Other	(2.5		)	(2.0		)
Other expense, net	$	(14.1	)	$	(15.7	)

Restructuring (Benefits) Charges (Tables)

3 Months Ended

Mar. 31, 2018

Restructuring and Related Activities [Abstract]

Schedule of restructuring liabilities



	December 31, 2017		Benefits			Cash Payments			Other		March 31, 2018
Severance	$	17.7	$	(0.9	)	$	(14.2	)	$	0.1	$	2.7
Contract terminations and other	2.3		(1.0		)	(1.3		)	—		—
Total	$	20.0	$	(1.9	)	$	(15.5	)	$	0.1	$	2.7

The Company does not anticipate future charges under the 2017 Restructuring Plan and expects to pay the remaining restructuring liabilities in the second quarter of 2018, at which time, the Company would consider the 2017 Restructuring Plan to be substantially completed.

Equity (Tables)

3 Months Ended

Mar. 31, 2018

Stockholders' Equity Note [Abstract]

Schedule of repurchase agreements

The following table summarizes the Company's stock repurchases and retirements, including prepayment pursuant to the ASR, under its stock repurchase programs (in millions, except per share amounts):



	Three Months Ended March 31,
	2018 ⁽¹⁾		2017 ⁽²⁾
Repurchases Under Stock Repurchase Program
Shares repurchased	23.3		4.5
Average price per share	$	25.80	$	28.03
Amount repurchased	$	750.0	$	125.0

________________________________

⁽¹⁾Shares repurchased under the 2018 Stock Repurchase Program.

⁽²⁾Shares repurchased under the 2014 Stock Repurchase Program.

Components of accumulated other comprehensive income, net of taxes

The components of accumulated other comprehensive income (loss), net of related taxes, for the three months ended March 31, 2018 were as follows (in millions):



	Unrealized Gains/Losses on Available-for- Sale Debt Securities⁽¹⁾			Unrealized Gains on Cash Flow Hedges⁽²⁾			Foreign Currency Translation Adjustments			Total
Balance as of December 31, 2017	$	19.0		$	6.0		$	(30.4	)	$	(5.4	)
Other comprehensive income before reclassifications	(2.0		)	13.1			5.3			16.4
Amount reclassified from accumulated other comprehensive income (loss)	0.9			(5.1		)	—			(4.2		)
Reclassification of tax effects upon adoption of ASU 2018-02	5.0			0.7			—			5.7
Other comprehensive income, net	3.9			8.7			5.3			17.9
Balance as of March 31, 2018	$	22.9		$	14.7		$	(25.1	)	$	12.5

________________________________


⁽¹⁾	The reclassifications out of accumulated other comprehensive income (loss) during the three months ended March 31, 2018 for realized losses on available-for-sale debt securities were included in other expense, net, in the Condensed Consolidated Statements of Operations.


⁽²⁾	The reclassifications out of accumulated other comprehensive income (loss) during the three months ended March 31, 2018 for realized gains on cash flow hedges were included within cost of revenues, research and development, sales and marketing, and general and administrative in the Condensed Consolidated Statements of Operations and were not material individually.

Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of share-based compensation, stock options, activity

The following table summarizes the Company’s stock option activity and related information as of and for the three months ended March 31, 2018 (in millions, except for per share amounts and years):



	Outstanding Options
	Number of Shares		Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term (In Years)	Aggregate Intrinsic Value
Balance as of December 31, 2017	0.9		$	34.41
Expired/Canceled	(0.6	)	40.75
Balance as of March 31, 2018	0.3		$	20.02	2.5	$	1.9

As of March 31, 2018:
Vested and expected-to-vest options	0.3		$	20.02	2.5	$	1.9
Exercisable options	0.2		$	21.87	1.8	$	1.4

Schedule of nonvested share activity

The Company’s RSU, restricted stock award ("RSA"), and PSA activity and related information as of and for the three months ended March 31, 2018 were as follows (in millions, except per share amounts and years):



	Outstanding RSUs, RSAs, and PSAs⁽⁴⁾
	Number of Shares		Weighted Average Grant-Date Fair Value per Share		Weighted Average Remaining Contractual Term (In Years)	Aggregate Intrinsic Value
Balance as of December 31, 2017	19.5		$	25.39
RSUs granted ⁽¹⁾⁽³⁾	4.9		25.11
PSAs granted⁽²⁾⁽³⁾	0.7		24.43
RSUs vested	(4.5	)	25.42
PSAs vested	(1.1	)	24.13
RSUs canceled	(0.5	)	26.36
PSAs canceled	(0.6	)	24.26
Balance as of March 31, 2018	18.4		$	25.35	1.4	$	448.0

________________________________

⁽¹⁾

Includes service-based and market-based RSUs. The number of shares subject to market-based condition 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 market-based condition that would be issued if market criteria determined by the Compensation Committee of the Board are achieved at target is 0.1 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 0.3 million shares.

⁽²⁾

The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee of the Board are achieved at target is 0.4 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 0.7 million shares.

⁽³⁾

The grant date fair value of RSUs and PSAs were reduced by the present value of dividends expected to be paid on the underlying shares of common stock during the requisite and derived service period as these awards are not entitled to receive dividends until vested. During the three months ended March 31, 2018, the Company declared a quarterly cash dividend of $0.18 per share of common stock on January 30, 2018.

⁽⁴⁾

Excludes 1.9 million shares of PSAs that were modified during the three months ended March 31, 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 $5.6 million to be recognized over the remaining terms of the modified awards.

Schedule of employee service share-based compensation, allocation of recognized period costs

Share-based compensation expense associated with stock options, RSUs, RSAs, PSAs, and ESPP was recorded in the following cost and expense categories in the Condensed Consolidated Statements of Operations (in millions):



	Three Months Ended March 31,
	2018		2017
Cost of revenues - Product	$	1.9	$	0.9
Cost of revenues - Service	4.8		4.3
Research and development	44.1		34.8
Sales and marketing	13.5		15.3
General and administrative	6.1		6.7
Total	$	70.4	$	62.0

Disclosure of share-based compensation arrangements by share-based payment award

The following table summarizes share-based compensation expense by award type (in millions):



	Three Months Ended March 31,
	2018		2017
Stock options	$	0.1	$	0.1
RSUs, RSAs, and PSAs	65.6		57.8
ESPP	4.7		4.1
Total	$	70.4	$	62.0

Segments (Tables)

3 Months Ended

Mar. 31, 2018

Segment Reporting [Abstract]

Financial information for each segment

The following table presents net revenues by product and service (in millions):



	Three Months Ended March 31,
	2018		2017
Routing	$	408.1	$	521.6
Switching	230.0		241.6
Security	72.7		65.7
Total product	710.8		828.9

Total service	371.8		392.1
Total	$	1,082.6	$	1,221.0

The following table presents net revenues by customer vertical (in millions):



	Three Months Ended March 31,
	2018		2017
Cloud	$	268.3	$	331.6
Service Provider	479.9		568.5
Enterprise	334.4		320.9
Total	$	1,082.6	$	1,221.0

Disaggregation of revenue

The following table presents net revenues by product and service (in millions):



	Three Months Ended March 31,
	2018		2017
Routing	$	408.1	$	521.6
Switching	230.0		241.6
Security	72.7		65.7
Total product	710.8		828.9

Total service	371.8		392.1
Total	$	1,082.6	$	1,221.0

The following table presents net revenues by customer vertical (in millions):



	Three Months Ended March 31,
	2018		2017
Cloud	$	268.3	$	331.6
Service Provider	479.9		568.5
Enterprise	334.4		320.9
Total	$	1,082.6	$	1,221.0

The Company attributes revenues to geographic region based on the customer’s shipping address. The following table presents net revenues by geographic region (in millions):



	Three Months Ended March 31,
	2018		2017
Americas:
United States	$	532.3	$	658.1
Other	55.3		53.5
Total Americas	587.6		711.6
Europe, Middle East, and Africa	308.0		284.5
Asia Pacific	187.0		224.9
Total	$	1,082.6	$	1,221.0

Net revenues by geographic region

The Company attributes revenues to geographic region based on the customer’s shipping address. The following table presents net revenues by geographic region (in millions):



	Three Months Ended March 31,
	2018		2017
Americas:
United States	$	532.3	$	658.1
Other	55.3		53.5
Total Americas	587.6		711.6
Europe, Middle East, and Africa	308.0		284.5
Asia Pacific	187.0		224.9
Total	$	1,082.6	$	1,221.0

Income Taxes (Tables)

3 Months Ended

Mar. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of effective income tax rate reconciliation

The following table provides details of income taxes (in millions, except percentages):



	Three Months Ended March 31,
	2018			2017
Income before income taxes	$	41.4		$	140.6
Income tax provision	$	7.0		$	31.8
Effective tax rate	16.9		%	22.6		%

Net Income Per Share (Tables)

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Schedule of earnings per share, basic and diluted

The Company computed basic and diluted net income per share as follows (in millions, except per share amounts):



	Three Months Ended March 31,
	2018		2017
Numerator:
Net income	$	34.4	$	108.8
Denominator:
Weighted-average shares used to compute basic net income per share	355.3		380.9
Dilutive effect of employee stock awards	5.3		7.1
Weighted-average shares used to compute diluted net income per share	360.6		388.0
Net income per share
Basic	$	0.10	$	0.29
Diluted	$	0.10	$	0.28

Anti-dilutive shares	10.4		1.6

Basis of Presentation (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Restricted cash and cash equivalents	$ 48.7	$ 47.4

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2018	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		$ 5.7
Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption	$ 5.7
Retained Earnings \| Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change on equity or net assets	313.5
Cumulative effect on retained earnings, tax	$ 61.4
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

Summary of Significant Accounting Policies (Contract Revenue Adjustments- Balance Sheet) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
ASSETS
Accounts receivable, net of allowances	$ 679.9	$ 850.1	$ 852.0
Prepaid expenses and other current assets	308.9	331.4	299.9
Other long-term assets	407.5	394.4	415.5
Total assets	9,078.5	9,842.3	9,833.8
Liabilities [Abstract]
Deferred revenue	888.2	818.6	1,030.3
Other accrued liabilities	230.5	335.6	304.3
Long-term deferred revenue	368.7	384.4	509.0
Total liabilities	4,753.8	4,847.9	5,152.9
Equity [Abstract]
Accumulated deficit	(3,303.3)	(3,042.3)	$ (3,355.8)
As reported/Without Adoption of Topic 606
ASSETS
Accounts receivable, net of allowances	674.6
Prepaid expenses and other current assets	280.4
Other long-term assets	402.2
Total assets	9,039.4
Liabilities [Abstract]
Deferred revenue	1,104.5
Other accrued liabilities	170.6
Long-term deferred revenue	484.5
Total liabilities	5,026.0
Equity [Abstract]
Accumulated deficit	(3,614.6)
Adjustments/ Topic 606 Impact
ASSETS
Prepaid expenses and other current assets	28.5
Other long-term assets	5.3
Total assets	39.1
Liabilities [Abstract]
Other accrued liabilities	59.9
Total liabilities	(272.2)
Adjustments/ Topic 606 Impact \| Accounting Standards Update 2014-09
ASSETS
Accounts receivable, net of allowances	5.3	(1.9)
Prepaid expenses and other current assets		31.5
Other long-term assets		(21.1)
Total assets		8.5
Liabilities [Abstract]
Deferred revenue	(216.3)	(211.7)
Other accrued liabilities		31.3
Long-term deferred revenue	(115.8)	(124.6)
Total liabilities		(305.0)
Equity [Abstract]
Accumulated deficit	$ 311.3	$ 313.5

Summary of Significant Accounting Policies (Contract revenue adjustment - Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net revenues:
Product	$ 710.8	$ 828.9
Service	371.8	392.1
Total net revenues	1,082.6	$ 1,221.0
Without Adoption of Topic 606
Net revenues:
Product	682.1
Service	398.6
Total net revenues	1,080.7
Topic 606 Impact \| Accounting Standards Update 2014-09
Net revenues:
Product	28.7
Service	(26.8)
Total net revenues	$ 1.9

Cash Equivalents and Investments - Available-For-Sale (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Available-for-sale debt securities:
Amortized Cost	$ 1,143.9	$ 2,386.3
Gross Unrealized Gains	37.4	37.9
Gross Unrealized Losses	(7.4)	(5.4)
Estimated Fair Value	1,173.9	2,418.8
Asset-backed securities
Available-for-sale debt securities:
Amortized Cost	118.6	287.1
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.7)	(0.6)
Estimated Fair Value	117.9	286.5
Certificates of deposit
Available-for-sale debt securities:
Amortized Cost	16.5	83.8
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	16.5	83.8
Commercial paper
Available-for-sale debt securities:
Amortized Cost	40.2	217.1
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	40.2	217.1
Corporate debt securities
Available-for-sale debt securities:
Amortized Cost	464.9	929.6
Gross Unrealized Gains	0.0	0.4
Gross Unrealized Losses	(5.1)	(3.0)
Estimated Fair Value	459.8	927.0
Foreign government debt securities
Available-for-sale debt securities:
Amortized Cost	24.5	62.9
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.2)	(0.2)
Estimated Fair Value	24.3	62.7
Time deposits
Available-for-sale debt securities:
Amortized Cost	265.6	239.2
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	265.6	239.2
U.S. government agency securities
Available-for-sale debt securities:
Amortized Cost	56.7	143.9
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.5)	(0.7)
Estimated Fair Value	56.2	143.2
U.S. government securities
Available-for-sale debt securities:
Amortized Cost	140.8	406.8
Gross Unrealized Gains	0.0	0.1
Gross Unrealized Losses	(0.9)	(0.9)
Estimated Fair Value	139.9	406.0
Fixed Income Securities
Available-for-sale debt securities:
Amortized Cost	1,127.8	2,370.4
Gross Unrealized Gains	0.0	0.5
Gross Unrealized Losses	(7.4)	(5.4)
Estimated Fair Value	1,120.4	2,365.5
Privately-held debt and redeemable preferred stock securities
Available-for-sale debt securities:
Amortized Cost	16.1	15.9
Gross Unrealized Gains	37.4	37.4
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	53.5	53.3
Cash equivalents
Available-for-sale debt securities:
Amortized Cost	286.2	351.0
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	286.2	351.0
Short-term investments
Available-for-sale debt securities:
Amortized Cost	318.9	1,027.2
Gross Unrealized Gains	0.0	0.1
Gross Unrealized Losses	(1.2)	(1.2)
Estimated Fair Value	317.7	1,026.1
Long-term investments
Available-for-sale debt securities:
Amortized Cost	522.7	992.2
Gross Unrealized Gains	0.0	0.4
Gross Unrealized Losses	(6.2)	(4.2)
Estimated Fair Value	516.5	988.4
Other long-term assets
Available-for-sale debt securities:
Amortized Cost	16.1	15.9
Gross Unrealized Gains	37.4	37.4
Gross Unrealized Losses	0.0	0.0
Estimated Fair Value	$ 53.5	$ 53.3

Cash Equivalents and Investments - Maturities of Fixed Income Investments (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Schedule of Fixed Income Securities Maturities [Abstract]
Amortized Cost	$ 1,143.9	$ 2,386.3
Total investments, estimated fair value	1,173.9	2,418.8
Fixed Income Securities
Schedule of Fixed Income Securities Maturities [Abstract]
Amortized cost due within one year	605.1
Amortized cost due between one and five years	522.7
Amortized Cost	1,127.8	2,370.4
Estimated fair value due within one year	603.9
Estimated fair value due between one and five year	516.5
Total investments, estimated fair value	$ 1,120.4	$ 2,365.5

Cash Equivalents and Investments - Narrative (Details)	3 Months Ended
Cash Equivalents and Investments - Narrative (Details)	Mar. 31, 2018 USD ($) Investment	Mar. 31, 2017 USD ($)
Cash Equivalents and Investments [Abstract]
Total investments in unrealized loss position \| Investment	583
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	$ 98,500,000
Prepaid expenses and other current assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	62,400,000
Restricted Cash and Investments, Noncurrent
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and investments	36,100,000
Debt Securities
Restricted Cash and Cash Equivalents Items [Line Items]
OTTI	$ 0	$ 0

Cash Equivalents and Investments - Unrealized Loss on Available-for-Sale Securities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fixed Income Securities
Fair Value
Less than 12 Months	$ 587.8	$ 1,238.3
12 Months or Greater	186.6	273.3
Total	774.4	1,511.6
Unrealized Loss
Less than 12 Months	5.4	3.6
12 Months or Greater	2.0	1.8
Total	7.4	5.4
Asset-backed securities
Fair Value
Less than 12 Months	90.7	215.2
12 Months or Greater	26.2	38.4
Total	116.9	253.6
Unrealized Loss
Less than 12 Months	0.5	0.4
12 Months or Greater	0.2	0.2
Total	0.7	0.6
Corporate debt securities
Fair Value
Less than 12 Months	359.4	646.7
12 Months or Greater	87.8	108.6
Total	447.2	755.3
Unrealized Loss
Less than 12 Months	4.0	2.1
12 Months or Greater	1.1	0.9
Total	5.1	3.0
Foreign government debt securities
Fair Value
Less than 12 Months	18.8	47.3
12 Months or Greater	5.5	6.6
Total	24.3	53.9
Unrealized Loss
Less than 12 Months	0.2	0.2
12 Months or Greater	0.0	0.0
Total	0.2	0.2
U.S. government agency securities
Fair Value
Less than 12 Months	21.9	68.3
12 Months or Greater	34.3	67.9
Total	56.2	136.2
Unrealized Loss
Less than 12 Months	0.1	0.2
12 Months or Greater	0.3	0.5
Total	0.4	0.7
U.S. government securities
Fair Value
Less than 12 Months	97.0	260.8
12 Months or Greater	32.8	51.8
Total	129.8	312.6
Unrealized Loss
Less than 12 Months	0.6	0.7
12 Months or Greater	0.4	0.2
Total	$ 1.0	$ 0.9

Cash Equivalents and Investments - Equity securities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity investments without readily determinable fair value	$ 30.4
Total equity securities	1,640.4
Equity investments without readily determinable fair value		$ 29.7
Total equity securities		1,027.1
Mutual funds
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity investments with readily determinable fair value	25.9
Equity investments with readily determinable fair value		27.6
Money market funds
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Equity investments with readily determinable fair value	1,584.1
Equity investments with readily determinable fair value		969.8
Cash equivalents
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Total equity securities	1,542.3
Total equity securities		928.0
Prepaid expenses and other current assets
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Total equity securities	34.6
Total equity securities		36.3
Other long-term assets
Debt Securities, Trading, and Equity Securities, FV-NI [Line Items]
Total equity securities	$ 63.5
Total equity securities		$ 62.8

Cash Equivalents and Investments - Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 2,614.2	$ 2,006.5
Restricted cash and cash equivalents			$ 48.7	$ 47.4
Total cash, cash equivalents and restricted cash and cash equivalents	2,645.0	2,059.1	$ 2,290.7	$ 1,880.6
Prepaid expenses and other current assets
Cash and Cash Equivalents [Line Items]
Restricted cash and cash equivalents	27.8	49.6
Other long-term assets
Cash and Cash Equivalents [Line Items]
Restricted cash and cash equivalents	$ 3.0	$ 3.0

Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Available-for-sale securities:
Available-for-sale debt securities	$ 1,173.9	$ 2,418.8
Asset-backed securities
Available-for-sale securities:
Available-for-sale debt securities	117.9	286.5
Certificates of deposit
Available-for-sale securities:
Available-for-sale debt securities	16.5	83.8
Commercial paper
Available-for-sale securities:
Available-for-sale debt securities	40.2	217.1
Corporate debt securities
Available-for-sale securities:
Available-for-sale debt securities	459.8	927.0
Foreign government debt securities
Available-for-sale securities:
Available-for-sale debt securities	24.3	62.7
Time deposits
Available-for-sale securities:
Available-for-sale debt securities	265.6	239.2
U.S. government agency securities
Available-for-sale securities:
Available-for-sale debt securities	56.2	143.2
U.S. government securities
Available-for-sale securities:
Available-for-sale debt securities	139.9	406.0
Privately-held debt and redeemable preferred stock securities
Available-for-sale securities:
Available-for-sale debt securities	53.5	53.3
Money market funds
Available-for-sale securities:
Equity securities	1,584.1
Equity securities		969.8
Fair Value, Measurements, Recurring
Available-for-sale securities:
Equity securities	1,610.0
Equity securities		997.4
Derivative assets:
Total assets measured at fair value	2,799.8	3,425.4
Liabilities measured at fair value:
Total liabilities measured at fair value	(0.7)	(1.8)
Fair Value, Measurements, Recurring \| Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	15.9	9.2
Liabilities measured at fair value:
Derivative liabilities	(0.7)	(1.8)
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Equity securities	1,610.0
Equity securities		997.4
Derivative assets:
Total assets measured at fair value	1,732.9	1,319.8
Liabilities measured at fair value:
Total liabilities measured at fair value	0.0	0.0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets For Identical Assets (Level 1) \| Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	0.0	0.0
Liabilities measured at fair value:
Derivative liabilities	0.0	0.0
Fair Value, Measurements, Recurring \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Equity securities	0.0
Equity securities		0.0
Derivative assets:
Total assets measured at fair value	1,013.4	2,052.3
Liabilities measured at fair value:
Total liabilities measured at fair value	(0.7)	(1.8)
Fair Value, Measurements, Recurring \| Significant Other Observable Remaining Inputs (Level 2) \| Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	15.9	9.2
Liabilities measured at fair value:
Derivative liabilities	(0.7)	(1.8)
Fair Value, Measurements, Recurring \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Equity securities	0.0
Equity securities		0.0
Derivative assets:
Total assets measured at fair value	53.5	53.3
Liabilities measured at fair value:
Total liabilities measured at fair value	0.0	0.0
Fair Value, Measurements, Recurring \| Significant Other Unobservable Remaining Inputs (Level 3) \| Foreign exchange contracts
Derivative assets:
Foreign exchange contracts	0.0	0.0
Liabilities measured at fair value:
Derivative liabilities	0.0	0.0
Fair Value, Measurements, Recurring \| Asset-backed securities
Available-for-sale securities:
Available-for-sale debt securities	117.9	286.5
Fair Value, Measurements, Recurring \| Asset-backed securities \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Asset-backed securities \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	117.9	286.5
Fair Value, Measurements, Recurring \| Asset-backed securities \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Certificates of deposit
Available-for-sale securities:
Available-for-sale debt securities	16.5	83.8
Fair Value, Measurements, Recurring \| Certificates of deposit \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Certificates of deposit \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	16.5	83.8
Fair Value, Measurements, Recurring \| Certificates of deposit \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Commercial paper
Available-for-sale securities:
Available-for-sale debt securities	40.2	217.1
Fair Value, Measurements, Recurring \| Commercial paper \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Commercial paper \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	40.2	217.1
Fair Value, Measurements, Recurring \| Commercial paper \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Corporate debt securities
Available-for-sale securities:
Available-for-sale debt securities	459.8	927.0
Fair Value, Measurements, Recurring \| Corporate debt securities \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Corporate debt securities \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	459.8	927.0
Fair Value, Measurements, Recurring \| Corporate debt securities \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Foreign government debt securities
Available-for-sale securities:
Available-for-sale debt securities	24.3	62.7
Fair Value, Measurements, Recurring \| Foreign government debt securities \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Foreign government debt securities \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	24.3	62.7
Fair Value, Measurements, Recurring \| Foreign government debt securities \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Time deposits
Available-for-sale securities:
Available-for-sale debt securities	265.6	239.2
Fair Value, Measurements, Recurring \| Time deposits \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Time deposits \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	265.6	239.2
Fair Value, Measurements, Recurring \| Time deposits \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| U.S. government agency securities
Available-for-sale securities:
Available-for-sale debt securities	56.2	143.2
Fair Value, Measurements, Recurring \| U.S. government agency securities \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| U.S. government agency securities \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	56.2	143.2
Fair Value, Measurements, Recurring \| U.S. government agency securities \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| U.S. government securities
Available-for-sale securities:
Available-for-sale debt securities	139.9	406.0
Fair Value, Measurements, Recurring \| U.S. government securities \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	122.9	322.4
Fair Value, Measurements, Recurring \| U.S. government securities \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	17.0	83.6
Fair Value, Measurements, Recurring \| U.S. government securities \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Privately-held debt and redeemable preferred stock securities
Available-for-sale securities:
Available-for-sale debt securities	53.5	53.3
Fair Value, Measurements, Recurring \| Privately-held debt and redeemable preferred stock securities \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Privately-held debt and redeemable preferred stock securities \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	0.0	0.0
Fair Value, Measurements, Recurring \| Privately-held debt and redeemable preferred stock securities \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	53.5	53.3
Fair Value, Measurements, Recurring \| Total available-for-sale debt securities
Available-for-sale securities:
Available-for-sale debt securities	1,173.9	2,418.8
Fair Value, Measurements, Recurring \| Total available-for-sale debt securities \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Available-for-sale debt securities	122.9	322.4
Fair Value, Measurements, Recurring \| Total available-for-sale debt securities \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Available-for-sale debt securities	997.5	2,043.1
Fair Value, Measurements, Recurring \| Total available-for-sale debt securities \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Available-for-sale debt securities	53.5	53.3
Fair Value, Measurements, Recurring \| Mutual funds
Available-for-sale securities:
Equity securities	25.9
Equity securities		27.6
Fair Value, Measurements, Recurring \| Mutual funds \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Equity securities	25.9
Equity securities		27.6
Fair Value, Measurements, Recurring \| Mutual funds \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Equity securities	0.0
Equity securities		0.0
Fair Value, Measurements, Recurring \| Mutual funds \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Equity securities	0.0
Equity securities		0.0
Fair Value, Measurements, Recurring \| Money market funds
Available-for-sale securities:
Equity securities	1,584.1
Equity securities		969.8
Fair Value, Measurements, Recurring \| Money market funds \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Available-for-sale securities:
Equity securities	1,584.1
Equity securities		969.8
Fair Value, Measurements, Recurring \| Money market funds \| Significant Other Observable Remaining Inputs (Level 2)
Available-for-sale securities:
Equity securities	0.0
Equity securities		0.0
Fair Value, Measurements, Recurring \| Money market funds \| Significant Other Unobservable Remaining Inputs (Level 3)
Available-for-sale securities:
Equity securities	0.0
Equity securities		0.0
Cash equivalents
Available-for-sale securities:
Available-for-sale debt securities	286.2	351.0
Cash equivalents \| Fair Value, Measurements, Recurring
Derivative assets:
Total assets measured at fair value	1,828.5	1,279.0
Cash equivalents \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Derivative assets:
Total assets measured at fair value	1,542.3	928.1
Cash equivalents \| Fair Value, Measurements, Recurring \| Significant Other Observable Remaining Inputs (Level 2)
Derivative assets:
Total assets measured at fair value	286.2	350.9
Cash equivalents \| Fair Value, Measurements, Recurring \| Significant Other Unobservable Remaining Inputs (Level 3)
Derivative assets:
Total assets measured at fair value	0.0	0.0
Short-term investments
Available-for-sale securities:
Available-for-sale debt securities	317.7	1,026.1
Short-term investments \| Fair Value, Measurements, Recurring
Derivative assets:
Total assets measured at fair value	317.7	1,026.1
Short-term investments \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Derivative assets:
Total assets measured at fair value	77.1	247.5
Short-term investments \| Fair Value, Measurements, Recurring \| Significant Other Observable Remaining Inputs (Level 2)
Derivative assets:
Total assets measured at fair value	240.6	778.6
Short-term investments \| Fair Value, Measurements, Recurring \| Significant Other Unobservable Remaining Inputs (Level 3)
Derivative assets:
Total assets measured at fair value	0.0	0.0
Long-term investments
Available-for-sale securities:
Available-for-sale debt securities	516.5	988.4
Long-term investments \| Fair Value, Measurements, Recurring
Derivative assets:
Total assets measured at fair value	516.5	988.4
Long-term investments \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Derivative assets:
Total assets measured at fair value	45.8	74.8
Long-term investments \| Fair Value, Measurements, Recurring \| Significant Other Observable Remaining Inputs (Level 2)
Derivative assets:
Total assets measured at fair value	470.7	913.6
Long-term investments \| Fair Value, Measurements, Recurring \| Significant Other Unobservable Remaining Inputs (Level 3)
Derivative assets:
Total assets measured at fair value	0.0	0.0
Prepaid expenses and other current assets \| Fair Value, Measurements, Recurring
Derivative assets:
Total assets measured at fair value	50.5	45.5
Prepaid expenses and other current assets \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Derivative assets:
Total assets measured at fair value	34.6	36.3
Prepaid expenses and other current assets \| Fair Value, Measurements, Recurring \| Significant Other Observable Remaining Inputs (Level 2)
Derivative assets:
Total assets measured at fair value	15.9	9.2
Prepaid expenses and other current assets \| Fair Value, Measurements, Recurring \| Significant Other Unobservable Remaining Inputs (Level 3)
Derivative assets:
Total assets measured at fair value	0.0	0.0
Other long-term assets \| Fair Value, Measurements, Recurring
Derivative assets:
Total assets measured at fair value	86.6	86.4
Other long-term assets \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Derivative assets:
Total assets measured at fair value	33.1	33.1
Other long-term assets \| Fair Value, Measurements, Recurring \| Significant Other Observable Remaining Inputs (Level 2)
Derivative assets:
Total assets measured at fair value	0.0	0.0
Other long-term assets \| Fair Value, Measurements, Recurring \| Significant Other Unobservable Remaining Inputs (Level 3)
Derivative assets:
Total assets measured at fair value	53.5	53.3
Other accrued liabilities \| Fair Value, Measurements, Recurring
Liabilities measured at fair value:
Total liabilities measured at fair value	(0.7)	(1.8)
Other accrued liabilities \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets For Identical Assets (Level 1)
Liabilities measured at fair value:
Total liabilities measured at fair value	0.0	0.0
Other accrued liabilities \| Fair Value, Measurements, Recurring \| Significant Other Observable Remaining Inputs (Level 2)
Liabilities measured at fair value:
Total liabilities measured at fair value	(0.7)	(1.8)
Other accrued liabilities \| Fair Value, Measurements, Recurring \| Significant Other Unobservable Remaining Inputs (Level 3)
Liabilities measured at fair value:
Total liabilities measured at fair value	$ 0.0	$ 0.0

Fair Value Measurements - Narrative (Details) - USD ($)	3 Months Ended
Fair Value Measurements - Narrative (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Investments	$ 41,800,000		$ 41,800,000
Goodwill and intangible impairment	0
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial and nonfinancial liabilities, fair value disclosure	0		0
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	2,200,000,000		2,252,900,000
Privately-held debt and redeemable preferred stock securities \| Significant Other Unobservable Remaining Inputs (Level 3) \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss) on investments	0	$ 0
Junos Pulse
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Note receivable	$ 61,200,000		$ 61,200,000

Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended
Derivative Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Derivatives, Notional Amount [Line Items]
Notional amount of foreign currency derivatives	$ 536.0		$ 629.4
Gain reclassified	5.6
Non-designated derivatives
Derivatives, Notional Amount [Line Items]
Notional amount of foreign currency derivatives	157.7		108.3
Cash flow hedges \| Designated as hedge
Derivatives, Notional Amount [Line Items]
Notional amount of foreign currency derivatives	$ 378.3		$ 521.1
Maturities of cash flow hedge derivatives	18 months
Gains or losses is expected to be reclassified into earnings within the next 12 months	$ 15.9
Foreign exchange contracts \| Cash flow hedges
Derivatives, Notional Amount [Line Items]
Derivative instruments, gain (loss) recognized in other comprehensive income (loss), Effective portion	$ 13.4	$ 7.0

Other Financial Information - Inventories, Net (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Schedule Of Inventory [Line Items]
Production and service materials	$ 62.9	$ 71.2
Finished goods	33.1	26.6
Inventory	96.0	97.8
Prepaid expenses and other current assets
Schedule Of Inventory [Line Items]
Inventory	92.6	93.8
Other long-term assets
Schedule Of Inventory [Line Items]
Inventory	$ 3.4	$ 4.0

Other Financial Information - Warranties (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance as of December 31, 2017	$ 27.4
Provisions made during the period	8.2
Actual costs incurred during the period	(8.3)
Balance as of March 31, 2018	$ 27.3

Other Financial Information - Deferred Revenue (Details) - USD ($) $ in Millions	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Reported as:
Current	$ 888.2	$ 818.6	$ 1,030.3
Long-term	368.7	$ 384.4	509.0
Deferred revenue	1,256.9		1,539.3
Undelivered product commitments and other product deferrals
Deferred product revenue:
Deferred gross product revenue	166.4		312.6
Distributor inventory and other sell-through items
Deferred product revenue:
Deferred gross product revenue	0.0		68.1
Product
Deferred product revenue:
Deferred gross product revenue	166.4		380.7
Deferred cost of product revenue	(7.6)		(46.5)
Reported as:
Deferred revenue	158.8		334.2
Service
Reported as:
Deferred revenue	$ 1,098.1		$ 1,205.1

Other Financial Information - Other Income (Expense), Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Other Financial Information [Abstract]
Interest income	$ 14.9	$ 10.4
Interest expense	(26.0)	(25.3)
(Loss) gain on investments, net	(0.5)	1.2
Other	(2.5)	(2.0)
Other expense, net	$ (14.1)	$ (15.7)

- Definition

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments.

+ References + Details

Other Financial Information (Revenue) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Disaggregation of Revenue [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	11 months 29 days
Revenue Recognition Expected by Period	$ 895.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01 \| Product
Disaggregation of Revenue [Line Items]
Revenue Recognition Expected by Period	144.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01 \| Service
Disaggregation of Revenue [Line Items]
Revenue Recognition Expected by Period	$ 751.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Disaggregation of Revenue [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	2 years
Revenue Recognition Expected by Period	$ 343.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01 \| Product
Disaggregation of Revenue [Line Items]
Revenue Recognition Expected by Period	19.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01 \| Service
Disaggregation of Revenue [Line Items]
Revenue Recognition Expected by Period	$ 324.2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01
Disaggregation of Revenue [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period
Revenue Recognition Expected by Period	$ 25.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01 \| Product
Disaggregation of Revenue [Line Items]
Revenue Recognition Expected by Period	3.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01 \| Service
Disaggregation of Revenue [Line Items]
Revenue Recognition Expected by Period	22.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Disaggregation of Revenue [Line Items]
Revenue Recognition Expected by Period	1,264.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil) \| Product
Disaggregation of Revenue [Line Items]
Revenue Recognition Expected by Period	166.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil) \| Service
Disaggregation of Revenue [Line Items]
Revenue Recognition Expected by Period	$ 1,098.1

Other Financial Information (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Deferred commission	$ 30.9
Amortization of deferred commission	40.5
Impairment loss	0.0
Product
Disaggregation of Revenue [Line Items]
Contract with customer, liability, revenue recognized	39.5
Service
Disaggregation of Revenue [Line Items]
Contract with customer, liability, revenue recognized	$ 265.0

Restructuring (Benefits) Charges (Charges and Changes to Restructuring)(Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance	$ 20.0
Benefits	(1.9)	$ 19.4
Cash Payments	(15.5)
Other	0.1
Restructuring liability, ending balance	2.7
Severance
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance	17.7
Benefits	(0.9)
Cash Payments	(14.2)
Other	0.1
Restructuring liability, ending balance	2.7
Contract terminations and other
Restructuring Reserve [Roll Forward]
Restructuring liability, beginning balance	2.3
Benefits	(1.0)
Cash Payments	(1.3)
Other	0.0
Restructuring liability, ending balance	$ 0.0

Financing Arrangements - Customer Financing Arrangements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Sale of receivable	$ 35.8	$ 25.4
Proceeds from sale and collection of receivables	33.0	$ 23.1
Receivables from sale of receivables	$ 16.5		$ 13.7
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of days due from receivable	1 day
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of days due from receivable	90 days

Equity - Cash Dividends on Shares of Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Mar. 22, 2018	Jan. 30, 2018	Mar. 31, 2018	Mar. 31, 2017
Stockholders' Equity Note [Abstract]
Cash dividends declared per common stock (in dollars per share)		$ 0.18	$ 0.18	$ 0.10
Common stock dividends paid	$ 62.1

Equity - Stock Repurchase Activities (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Feb. 28, 2018	Jan. 31, 2018
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount				$ 2,000,000,000.0
Payment to repurchase stock	$ 754,200,000	$ 129,700,000
Payments for derivative instrument	150,000,000
Stock repurchase program, remaining authorized repurchase amount	1,300,000,000
Accelerated Share Repurchase Program
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount			$ 750,000,000	$ 750,000,000
Payment to repurchase stock	$ 750,000,000
Stock repurchased (in shares)	23.3
Amount repurchased	$ 600,000,000
Stock Repurchase Program
Accelerated Share Repurchases [Line Items]
Stock repurchased (in shares)	23.3	4.5
Average price per share (in dollars per share)	$ 25.80	$ 28.03
Amount repurchased	$ 750,000,000	$ 125,000,000

Equity - Components of Accumulated Other Comprehensive (Loss) Income, Net of Tax (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income before reclassifications	$ 16.4
Amount reclassified from accumulated other comprehensive income (loss)	(4.2)
Reclassification of tax effects upon adoption of ASU No. 2018-02	5.7
Other comprehensive income, net	17.9
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of December 31, 2017	(5.4)
Balance as of March 31, 2018	12.5
Unrealized Gains on Available-for- Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of December 31, 2017	19.0
Other comprehensive income before reclassifications	(2.0)
Amount reclassified from accumulated other comprehensive income (loss)	0.9
Reclassification of tax effects upon adoption of ASU No. 2018-02	5.0
Other comprehensive income, net	3.9
Balance as of March 31, 2018	22.9
Unrealized (Losses) Gains on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of December 31, 2017	6.0
Other comprehensive income before reclassifications	13.1
Amount reclassified from accumulated other comprehensive income (loss)	(5.1)
Reclassification of tax effects upon adoption of ASU No. 2018-02	0.7
Other comprehensive income, net	8.7
Balance as of March 31, 2018	14.7
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance as of December 31, 2017	(30.4)
Other comprehensive income before reclassifications	5.3
Amount reclassified from accumulated other comprehensive income (loss)	0.0
Reclassification of tax effects upon adoption of ASU No. 2018-02	0.0
Other comprehensive income, net	5.3
Balance as of March 31, 2018	$ (25.1)

Employee Benefit Plans ( Equity Incentive Plan and Stock Option Activity) (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares
Number of Shares
Balance at beginning of period (in shares)	0.9
Expired/canceled (in shares)	(0.6)
Balance at end of period (in shares)	0.3
Weighted Average Exercise Price per Share
Balance at beginning of period (in dollars per share) \| $ / shares	$ 34.41
Expired/canceled (in dollars per share) \| $ / shares	40.75
Balance at end of period (in dollars per share) \| $ / shares	$ 20.02
Weighted average remaining contractual term at end of period	2 years 5 months 16 days
Aggregate intrinsic value at end of period \| $	$ 1.9
Vested or expected-to-vest options at end of period (in shares)	0.3
Vested or expected-to-vest options, weighted average exercise price at end of period (in dollars per share) \| $ / shares	$ 20.02
Vested and expected-to-vest options, weighted average remaining contractual term at end of period	2 years 5 months 16 days
Vested or expected-to-vest options, aggregate intrinsic value at end of period \| $	$ 1.9
Exercisable options at end of period (in shares)	0.2
Exercisable options, weighted average exercise price at end of period (in dollars per share) \| $ / shares	$ 21.87
Exercisable options, weighted average remaining contractual term at end of period	1 year 9 months 19 days
Exercisable options, aggregate intrinsic value at end of period \| $	$ 1.4
Equity incentive plan 2015
Share-Based Compensation Plans
Number of shares available for future issuance	24.3
Employee stock purchase plan 2008
Share-Based Compensation Plans
Number of shares available for future issuance	9.9

Employee Benefit Plans (ESPP) (Details) shares in Millions		3 Months Ended
Employee Benefit Plans (ESPP) (Details) shares in Millions	Nov. 06, 2017 period	Mar. 31, 2018 $ / shares shares	Mar. 31, 2017 $ / shares shares
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
ESPP offering period duration (in months)	24 months
ESPP, number of offering period \| period	4
ESPP. purchase period (in months)	6 months
ESPP, purchase price of common stock (in percent)	85.00%
ESPP, rolling years	2 years
Employee stock purchase plan 2008
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Stock issued during period, shares, employee stock purchase plans (in shares) \| shares		1.3	1.5
Average price of common stock, per share (in dollars per share) \| $ / shares		$ 22.23	$ 19.21

Employee Benefit Plans - Equity Instruments Other Than Options (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
	Jan. 30, 2018	Mar. 31, 2018	Mar. 31, 2017
Weighted Average Grant-Date Fair Value per Share
Cash dividends declared per common stock (in dollars per share)	$ 0.18	$ 0.18	$ 0.10
RSUs, RSAs, and PSAs
Number of Shares
Balance at beginning of period (in shares)		19.5
Balance at end of period (in shares)		18.4
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)		$ 25.35
Weighted Average Remaining Contractual Term (In Years)		1 year 4 months 24 days
Aggregate Intrinsic Value		$ 448.0
Restricted Stock Units (RSUs)
Number of Shares
Granted (in shares)		4.9
Vested (in shares)		(4.5)
Canceled (in shares)		(0.5)
Weighted Average Grant-Date Fair Value per Share
Granted (in dollars per share)		$ 25.11
Vested (in dollars per share)		25.42
Canceled (in dollars per share)		$ 26.36
Performance goal, number of shares ( in shares)		0.1
Performance shares (PSAs)
Number of Shares
Granted (in shares)		0.7
Vested (in shares)		(1.1)
Canceled (in shares)		(0.6)
Weighted Average Grant-Date Fair Value per Share
Granted (in dollars per share)		$ 24.43
Vested (in dollars per share)		24.13
Canceled (in dollars per share)		$ 24.26
Performance goal, number of shares ( in shares)		0.4
Number of shares modified		1.9
Incremental compensation cost resulting from the modifications		$ 5.6
Minimum \| Restricted Stock Units (RSUs)
Weighted Average Grant-Date Fair Value per Share
Performance goal, number of shares ( in shares)		0.0
Minimum \| Performance shares (PSAs)
Weighted Average Grant-Date Fair Value per Share
Performance goal, number of shares ( in shares)		0.0
Maximum \| Restricted Stock Units (RSUs)
Weighted Average Grant-Date Fair Value per Share
Performance goal, number of shares ( in shares)		0.3
Maximum \| Performance shares (PSAs)
Weighted Average Grant-Date Fair Value per Share
Performance goal, number of shares ( in shares)		0.7

Employee Benefit Plans - Share Based Compensation by Cost and Expense Categories (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	$ 70.4	$ 62.0
Stock options
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	0.1	0.1
RSUs, RSAs, and PSAs
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	65.6	57.8
ESPP
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	4.7	4.1
Cost of revenues - Product
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	1.9	0.9
Cost of revenues - Service
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	4.8	4.3
Research and development
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	44.1	34.8
Sales and marketing
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	13.5	15.3
General and administrative
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-based compensation expense	$ 6.1	$ 6.7

Employee Benefit Plans - Share Based Compensation by Share Based Payment Award Types (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Cost	$ 413.9
Weighted Average Period (In Years)	1 year 10 months 13 days

Segments (Revenue by product) (Details) $ in Millions	3 Months Ended
Segments (Revenue by product) (Details) $ in Millions	Mar. 31, 2018 USD ($) segment	Mar. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	1
Revenue	$ 1,082.6	$ 1,221.0
Revenue, Net	1,082.6	1,221.0
Product
Segment Reporting Information [Line Items]
Revenue	710.8	828.9
Routing
Segment Reporting Information [Line Items]
Revenue	408.1	521.6
Switching
Segment Reporting Information [Line Items]
Revenue	230.0	241.6
Security
Segment Reporting Information [Line Items]
Revenue	72.7	65.7
Service
Segment Reporting Information [Line Items]
Revenue	$ 371.8	$ 392.1

Segments - Revenues by Customer Vertical (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 1,082.6	$ 1,221.0
Revenue, Net	1,082.6	1,221.0
Cloud
Segment Reporting Information [Line Items]
Revenue	268.3	331.6
Service Provider
Segment Reporting Information [Line Items]
Revenue	479.9	568.5
Enterprise
Segment Reporting Information [Line Items]
Revenue	$ 334.4	$ 320.9

Segments - Geographic (Details) - USD ($) $ in Millions	3 Months Ended
Segments - Geographic (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 1,082.6	$ 1,221.0
Revenue, Net	1,082.6	1,221.0
Total Americas
Segment Reporting Information [Line Items]
Revenue	587.6	711.6
United States
Segment Reporting Information [Line Items]
Revenue	532.3	658.1
Other
Segment Reporting Information [Line Items]
Revenue	55.3	53.5
Europe, Middle East, and Africa
Segment Reporting Information [Line Items]
Revenue	308.0	284.5
Asia Pacific
Segment Reporting Information [Line Items]
Revenue	$ 187.0	$ 224.9

Income Taxes (Details of Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income before income taxes	$ 41.4	$ 140.6
Income tax provision	$ 7.0	$ 31.8
Effective tax rate	16.90%	22.60%
Discrete benefit (in percentage)	4.40%
Unrecognized tax benefits	$ 263.1
Unrecognized tax benefits could decrease up to	$ 45.8

Net Income Per Share (Basic and Diluted Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income	$ 34.4	$ 108.8
Denominator:
Weighted-average shares used to compute basic net income per share (in shares)	355.3	380.9
Dilutive effect of employee stock awards (in shares)	5.3	7.1
Weighted-average shares used to compute diluted net income per share (in shares)	360.6	388.0
Net income per share
Basic (in dollars per share)	$ 0.10	$ 0.29
Diluted, (in dollars per share)	$ 0.10	$ 0.28
Anti-dilutive shares	10.4	1.6

Commitments and Contingencies - Commitments (Details) $ in Millions	Mar. 31, 2018 USD ($)
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase Obligation	$ 616.6
Accrued Estimate Carrying Charges Or Obsolete Materials Charges	$ 25.8

Commitments and Contingencies - Guarantees (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Indemnification Agreement
Guarantor Obligations [Line Items]
Guarantor obligations, current carrying value	$ 9.4	$ 20.4

Subsequent Events (Details) - USD ($) $ / shares in Units, shares in Millions			3 Months Ended
	May 02, 2018	Jan. 30, 2018	Mar. 31, 2018	Mar. 31, 2017	Feb. 28, 2018	Jan. 31, 2018
Subsequent Event [Line Items]
Cash dividends declared per common stock (in dollars per share)		$ 0.18	$ 0.18	$ 0.10
Stock repurchase program, remaining authorized repurchase amount			$ 1,300,000,000
Stock Repurchase Program, Authorized Amount						$ 2,000,000,000.0
Subsequent Event
Subsequent Event [Line Items]
Cash dividends declared per common stock (in dollars per share)	$ 0.18
Accelerated Share Repurchase Program
Subsequent Event [Line Items]
Shares settled (in shares)			23.3
Amount repurchased			$ 600,000,000
Stock Repurchase Program, Authorized Amount					$ 750,000,000	$ 750,000,000