Juniper Networks (JNPR) 10-K 20 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 13, 2015	Jun. 30, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	JUNIPER NETWORKS INC
Entity Central Index Key	1043604
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		406,988,819
Entity Public Float			$11,331

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net revenues:
Product	$3,408.70	$3,519.90	$3,262.10
Service	1,218.40	1,149.20	1,103.30
Total net revenues	4,627.10	4,669.10	4,365.40
Cost of revenues:
Product	1,286.80	1,276.60	1,204
Service	482.1	451.1	452.6
Total cost of revenues	1,768.90	1,727.70	1,656.60
Gross margin	2,858.20	2,941.40	2,708.80
Operating expenses:
Research and development	1,006.20	1,043.20	1,101.60
Sales and marketing	1,023.60	1,075.90	1,045.50
General and administrative	231.1	217.3	206.8
Restructuring and other charges	167	39.1	46.8
Impairment of goodwill	850	0	0
Total operating expenses	3,277.90	2,375.50	2,400.70
Operating (loss) income	-419.7	565.9	308.1
Other income (expense), net	333.4	-40.4	-16.6
(Loss) income before income taxes	-86.3	525.5	291.5
Income tax provision	248	85.7	105
Net (loss) income	($334.30)	$439.80	$186.50
Net (loss) income per share:
Basic (in dollars per share)	($0.73)	$0.88	$0.36
Diluted (in dollars per share)	($0.73)	$0.86	$0.35
Shares used in computing net income per share:
Basic (in shares)	457.4	501.8	520.9
Diluted (in shares)	457.4	510.3	526.2
Cash dividends declared per common stock (in dollars per share)	$0.20	$0	$0

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net (loss) income	($334.30)	$439.80	$186.50
Available-for-sale securities:
Unrealized gains on available-for-sale securities, net of tax provision of ($29.5), ($37.9) and ($0.6) for 2014, 2013 and 2012, respectively	48.7	65.1	3.2
Reclassification adjustment for realized net gains on available-for- sale securities included in net (loss) income, net of tax provision of $61.8, $0.4 and $0.2 for 2014, 2013 and 2012, respectively	-106.5	-1	-1.2
Net change in unrealized gains on available-for-sale securities, net of taxes	-57.8	64.1	2
Cash flow hedges:
Unrealized (losses) gains on cash flow hedges, net of tax (provision) benefit of ($0.7), $1.7 and $0.2 for 2014, 2013 and 2012, respectively	-4.1	0.7	7.4
Reclassification adjustment for realized (gains) losses on cash flow hedges included in net (loss) income, net of tax provision (benefit) of $1.1, ($0.8) and ($1.0) for 2014, 2013 and 2012, respectively	-2.3	-1.5	6.5
Net change in unrealized (losses) gains on cash flow hedges, net of taxes	-6.4	-0.8	13.9
Change in foreign currency translation adjustments	-14.2	-3.4	6.4
Other comprehensive (loss) income, net of tax	-78.4	59.9	22.3
Comprehensive (loss) income	($412.70)	$499.70	$208.80

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income Parenthetical (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Tax provision on change in unrealized gains on available-for-sale securities	($29.50)	($37.90)	($0.60)
Tax provision on reclassification adjustment for realized net gains on available-for-sale securities included in net income	61.8	0.4	0.2
Tax benefit on change in unrealized gains (losses) on cash flow hedges	-0.7	1.7	0.2
Tax benefit on reclassification adjustment for realized losses (gains) included in net income	$1.10	($0.80)	($1)

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Current assets:
Cash and cash equivalents	$1,639.60	$2,284
Short-term investments	332.2	561.9
Accounts receivable, net of allowance for doubtful accounts of $4.7 and $5.4 as of December 31, 2014 and 2013, respectively	598.9	578.3
Deferred tax assets, net	147	79.8
Prepaid expenses and other current assets	254.2	199.9
Total current assets	2,971.90	3,703.90
Property and equipment, net	904.3	882.3
Long-term investments	1,133.10	1,251.90
Restricted cash and investments	46	89.5
Purchased intangible assets, net	62.4	106.9
Goodwill	2,981.50	4,057.70
Other long-term assets	303.9	233.8
Total assets	8,403.10	10,326
Current liabilities:
Accounts payable	234.6	200.4
Accrued compensation	225	273.9
Deferred revenue	780.8	705.8
Other accrued liabilities	287.3	261.3
Total current liabilities	1,527.70	1,441.40
Long-term debt	1,349	999.3
Long-term deferred revenue	294.9	363.5
Long-term income tax payable	177.5	114.4
Other long-term liabilities	134.9	105.2
Total liabilities	3,484	3,023.80
Commitments and contingencies (Note 16)
Juniper Networks stockholders' equity:
Convertible preferred stock, $0.00001 par value; 10.0 shares authorized; none issued and outstanding	0	0
Common stock, $0.00001 par value; 1,000.0 shares authorized; 416.2 shares and 495.2 shares issued and outstanding as of December 31, 2014 and 2013, respectively	0	0
Additional paid-in capital	8,794	9,868.90
Accumulated other comprehensive (loss) income	-13.8	64.6
Accumulated deficit	-3,861.10	-2,631.30
Total stockholders' equity	4,919.10	7,302.20
Total liabilities and stockholders' equity	$8,403.10	$10,326

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets Parentheticals (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Consolidated Balance Sheet Parenthetical [Abstract]
Convertible preferred stock - par value	$0.00	$0.00
Convertible preferred stock - shares authorized	10,000,000	10,000,000
Convertible preferred stock - issued	0	0
Convertible preferred stock - outstanding	0	0
Common stock - par value	$0.00	$0.00
Common stock - shares authorized	1,000,000,000	1,000,000,000
Common stock - issued	416,200,000	495,200,000
Common stock - outstanding	416,200,000	495,200,000
Allowance for doubtful accounts receivable, current	$4.70	$5.40

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net (loss) income	($334.30)	$439.80	$186.50
Adjustments to reconcile consolidated net income to net cash provided by operating activities:
Share-based compensation expense	240	244.6	242.7
Depreciation, amortization, and accretion	186.1	189.9	187.9
Restructuring and other charges	208.5	47.5	99.7
Deferred income taxes	-16.9	72.2	-18.2
Impairment of goodwill	850	0	0
Gain on sale of Junos Pulse	-19.6	0	0
(Gain) loss on investments, net	-167.9	-11.3	-26.7
Gain on legal settlement, net	-121.1	0	0
Excess tax benefits from share-based compensation	-9.4	-1.9	-7.2
Loss on disposal of fixed assets	1.7	1.4	0.6
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, net	-16.8	-139.9	139.1
Prepaid expenses and other assets	-24.5	-126	-11.4
Accounts payable	38.3	-8.9	-133.6
Accrued compensation	-46	-5.4	54.8
Income tax payable	51	-38.5	-7.5
Other accrued liabilities	-100.8	36.5	-15.4
Deferred revenue	45.1	145.9	-53.6
Net cash provided by operating activities	763.4	845.9	637.7
Cash flows from investing activities:
Purchases of property and equipment	-192.9	-230	-347.7
Proceeds from Divestiture of Businesses	105.7	0	0
Purchases of available-for-sale investments	-2,440.70	-1,776	-1,496.50
Proceeds from sales of available-for-sale investments	2,627.70	1,167.20	894.2
Proceeds from maturities of available-for-sale investments	337.6	334.6	559.7
Purchases of trading investments	-4.1	-3.7	-4.1
Proceeds from the sales of privately-held investments	4.9	9.4	36.5
Purchases of privately-held investments	-21.7	-41.3	-12.2
Payment for business acquisitions, net of cash and cash equivalents acquired	-27.1	-10	-139.4
Purchase of licensed software	0	-10	-65.3
Changes in restricted cash	44.6	-1.2	-20.8
Net cash used in investing activities	434	-561	-595.6
Cash flows from financing activities:
Proceeds from issuance of common stock	159.8	141.7	99.1
Purchases and retirement of common stock	-2,262.50	-577.8	-650.6
Issuance of long-term debt, net	346.5	0	0
Payment for capital lease obligation	-0.4	-1.4	-1.4
Customer financing arrangements	9	33.9	-2.6
Excess tax benefits from share-based compensation	9.4	1.9	7.2
Payment of cash dividends	-86	0	0
Net cash (used in) provided by financing activities	-1,824.20	-401.7	-548.3
Effect of foreign currency exchange rates on cash and cash equivalents	-17.6	-7	3.6
Net (decrease) increase in cash and cash equivalents	-644.4	-123.8	-502.6
Cash and cash equivalents at beginning of period	2,284	2,407.80	2,910.40
Cash and cash equivalents at end of period	1,639.60	2,284	2,407.80
Supplemental disclosures of cash flow information:
Cash paid for interest, net of amounts capitalized	44.9	57.4	50.1
Cash paid (received) for income taxes, net	206	105.1	118.7
Non-cash investing activities:
Receipt of a promissory note in connection with the sale of Junos Pulse	125	0	0
Issuance of common stock and equity awards assumed in business acquisitions	0	0	16.5
Property and equipment acquired under capital lease	0	0	3.7
Licensed software acquired	$0	$0	$19

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Stockholders' Equity (USD $)	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Noncontrolling Interest [Member]
In Millions, unless otherwise specified	USD ($)		USD ($)	USD ($)	USD ($)	USD ($)
Stockholders' equity, Beginning balance at Dec. 31, 2011	$7,089.70		$10,079.20	($17.60)	($2,972.40)	$0.50
Number of shares, Beginning balance at Dec. 31, 2011		526.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	186.5				186.5
Other comprehensive income (loss), net	22.3			22.3
Shares issued in connection with share-based compensation (in number of shares)		12.2
Shares issued in connection with share-based compensation	99.2		99.2
Shares assumed In connection with business acquisition, shares (in number of shares)		5.8
Shares assumed in connection with business acquisitions	16.5		16.5
Repurchase and retirement of common stock and net issuances (in number of shares)		-36
Repurchase and retirement of common stock and net issuances	-650.6		-525.1		-125.5
Share-based compensation expense	242.7		242.7
Tax benefit from employee stock option plans	-6.8		-6.8
Stockholders' equity, Ending balance at Dec. 31, 2012	6,999.50		9,905.70	4.7	-2,911.40	0.5
Number of shares, Ending balance at Dec. 31, 2012		508.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	439.8				439.8
Other comprehensive income (loss), net	59.9			59.9
Shares issued in connection with share-based compensation (in number of shares)		16
Shares issued in connection with share-based compensation	142.2		142.2
Dissolution of non-controlling interest	-0.5					-0.5
Repurchase and retirement of common stock and net issuances (in number of shares)		-29.2
Repurchase and retirement of common stock and net issuances	-577.8		-418.1		-159.7
Share-based compensation expense	244.9		244.9
Tax benefit from employee stock option plans	-5.8		-5.8
Stockholders' equity, Ending balance at Dec. 31, 2013	7,302.20		9,868.90	64.6	-2,631.30	0
Number of shares, Ending balance at Dec. 31, 2013		495.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	-334.3				-334.3
Other comprehensive income (loss), net	-78.4			-78.4
Shares issued in connection with share-based compensation (in number of shares)		17.7
Shares issued in connection with share-based compensation	159.1		159.1
Repurchase and retirement of common stock and net issuances (in number of shares)		-96.7
Repurchase and retirement of common stock and net issuances	-2,262.50		-1,367		-895.5
Share-based compensation expense	240		240
Tax benefit from employee stock option plans	-21		-21
Payment of cash dividends	-86		-86
Stockholders' equity, Ending balance at Dec. 31, 2014	$4,919.10		$8,794	($13.80)	($3,861.10)	$0
Number of shares, Ending balance at Dec. 31, 2014		416.2

Description_of_Business_and_Ba

Description of Business and Basis of Presentation (Notes)	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation
	Description of Business
	Juniper Networks, Inc. (the “Company” or “Juniper”) designs, develops, and sells products and services for high-performance networks, to enable customers to build scalable, reliable, secure and cost-effective networks for their businesses, while achieving agility, efficiency and value through automation. The Company serves the high-performance networking requirements for global service providers, cloud environments, enterprises, governments, and research and public sector organizations that view the network as critical to their success. In addition to the Company's products, the Company offers technical support and professional services, as well as education and training programs to its customers. Together, the high-performance product and service offerings help the Company's customers convert legacy networks that provide commoditized services into more valuable assets that provide differentiation, value, and increased performance, reliability, and security to end-users.
	Basis of Presentation
	The Consolidated Financial Statements, which include the Company and its wholly-owned subsidiaries, are prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). All intercompany balances and transactions have been eliminated. Certain amounts in the prior years' Consolidated Financial Statements have been reclassified to conform to the current year presentation.
	In 2014, the Company realigned its organization into a One-Juniper structure which includes consolidating each of the Company's research and development ("R&D") and go-to-market functions to reduce complexity, increase clarity of responsibilities, and improve efficiency. As a result of these changes, the Company's consolidated business is considered to be one reportable segment. In fiscal 2013, the Company operated under two reportable segments: Platform Systems Division ("PSD") and Software Solutions Division ("SSD"). This change did not impact previously reported consolidated results of operations. See Note 13, Segments, for further discussion of the Company's segment reorganization.

Significant_Accounting_Policie

Significant Accounting Policies (Notes)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies
	Use of Estimates
	The preparation of the financial statements and related disclosures in conformity with U.S. GAAP requires the Company to make judgments, assumptions, and estimates that affect the amounts reported in the Consolidated Financial Statements and the accompanying notes. The Company bases its estimates and assumptions on current facts, historical experience, and various other factors that it believes are reasonable under the circumstances, to determine the carrying values of assets and liabilities that are not readily apparent from other sources. To the extent there are material differences between the Company's estimates and the actual results, the Company's future consolidated results of operation may be affected.
	Cash, Cash Equivalents and Investments
	Cash and Cash Equivalents
	Cash and cash equivalents consist of cash on hand, demand deposits with banks, highly liquid investments in money market funds, commercial paper, government securities, certificates of deposit, and corporate debt securities, which are readily convertible into cash. All highly liquid investments purchased with original maturities of three months or less are classified as cash and cash equivalents.
	Investments in Available-for-Sale and Trading Securities
	The Company's investments in publicly-traded debt and equity securities are classified as available-for-sale. Available-for-sale investments are initially recorded at cost and periodically adjusted to fair value in the Consolidated Balance Sheets. Unrealized gains and losses on these investments are reported as a separate component of accumulated other comprehensive income. Realized gains and losses are determined based on the specific identification method and are reported in the Consolidated Statements of Operations.
	The Company periodically evaluates its investments to determine if impairment charges are required. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value has been less than the Company's cost basis, the investment's financial condition, and near-term prospects of the investee. If the Company determines that the decline in an investment's fair value is other than temporary, the difference is recognized as an impairment loss in its Consolidated Statements of Operations. The Company's non-qualified compensation plan is invested in mutual funds which are classified as trading securities and reported at fair value in the Consolidated Balance Sheets. The realized and unrealized holding gains and losses are reported in the Consolidated Statements of Operations.
	Privately-Held Investments
	The Company has privately-held investments, which are included in other long-term assets in the Consolidated Balance Sheets. These investments include debt and redeemable preferred stock securities that are carried at fair value, and non-redeemable preferred stock securities that are carried at cost. The investments carried at cost are adjusted for any impairment, as the Company does not have a controlling interest and does not have the ability to exercise significant influence over these companies. These investments are inherently high risk as the market for technologies or products manufactured by these companies are usually in their early stages at the time of the investment by the Company and such markets may never be significant. The Company measures the fair value of privately-held investments using an analysis of the financial conditions and near term prospects of the investees, including recent financing activities and their capital structure. Realized gains and losses, if any, are reported in the Consolidated Statements of Operations.
	Fair Value
	Fair value is defined as the price that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value, the Company considers the principal or most advantageous market in which it transacts, and considers assumptions that market participants would use when pricing the asset or liability. The Company applies the following fair value hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement:
	Level 1 – Quoted prices in active markets for identical assets or liabilities.
	Level 2 – Quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. These inputs are valued using market based approaches.
	Level 3 – Inputs are unobservable inputs based on the Company’s assumptions. These inputs, if any, are valued using internal financial models.
	Derivatives
	The Company uses derivatives to partially offset its market exposure to fluctuations in certain foreign currencies. The Company does not enter into derivatives for speculative or trading purposes.
	The Company uses foreign currency forward or option contracts to hedge certain forecasted foreign currency transactions relating to operating expenses. These derivatives are designated as cash flow hedges. Execution of these cash flow hedge derivatives typically occurs every month with maturities of one year or less. These derivatives are carried at fair value and the effective portion of the derivative's gain or loss is initially reported as a component of accumulated other comprehensive income, and upon occurrence of the forecasted transaction, is subsequently reclassified into the costs of services or operating expense line item to which the hedged transaction relates. The Company records any ineffectiveness of the hedging instruments in other income (expense), net, on its Consolidated Statements of Operations. Cash flows from such hedges are classified as operating activities. All amounts within other comprehensive income are expected to be reclassified into earnings within the next twelve months.
	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 derivatives are carried at fair value with changes recorded in other income (expense), net in the Consolidated Statements of Operations. Changes in the fair value of these derivatives are largely offset by remeasurement of the underlying assets and liabilities. Cash flows from such derivatives are classified as operating activities. These foreign exchange forward contracts have maturities of one year or less.
	Inventory
	Inventory consists primarily of component parts to be used in the manufacturing process and finished goods in-transit, and is stated at the lower of cost or market. Cost is computed using standard cost, which approximates actual cost, on a first-in, first-out basis. A charge is recorded to cost of product when inventory is determined to be in excess of anticipated demand or considered obsolete. At the point of loss recognition, a new, lower-cost basis for that inventory is established, and subsequent changes in facts and circumstances do not result in the restoration or increase in the newly established cost basis.
	Property and Equipment
	Property and equipment are recorded at cost less accumulated depreciation. Depreciation is calculated using the straight-line method, over the estimated useful lives of the following assets:
		Estimated Useful Life (years)
	Computers, equipment, and software	3 to 7
	Furniture and fixtures	5
	Building and building improvements	7 to 40
	Land improvements	5 to 40
	Leasehold improvements	Lease term, not to exceed 10 years
	Construction in progress is related to the construction or development of property and equipment that have not yet been placed in service for their intended use. Depreciation for equipment commences once it is placed in service and depreciation for buildings and leasehold improvements commences once they are ready for their intended use.
	Goodwill and Other Long-Lived Assets
	Goodwill represents the future economic benefits arising from other assets acquired in a business combination or an acquisition that are not individually identified and separately recorded. The excess of the purchase price over the estimated fair value of net assets of businesses acquired in a business combination is recognized as goodwill. Goodwill is tested for impairment annually during the fourth quarter or more frequently if certain circumstances change that would more likely than not indicate that the fair value of a reporting unit is below its carrying value. An impairment loss is recognized to the extent that the carrying amount of goodwill exceeds the asset's implied fair value. Other intangible assets acquired in a business combination and determined to have an indefinite useful life are not amortized but are assessed for potential impairment annually or when events or circumstances indicate that their carrying amounts might be impaired.
	Long-lived assets, such as property, plant, and equipment, and purchased intangible assets subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset, or asset group, to estimated undiscounted future cash flows expected to be generated by the asset, or asset group. An impairment charge is recognized by the amount by which the carrying amount of the asset, or asset group, exceeds its fair value.
	The Company amortizes intangible assets with estimable useful lives on a straight-line basis over their useful lives.
	Revenue Recognition
	Revenue is recognized when all of the following criteria have been met:
	•	Persuasive evidence of an arrangement exists. The Company generally relies upon sales contracts or agreements, and customer purchase orders to determine the existence of an arrangement.
	•	Delivery has occurred. The Company uses shipping terms and related documents, or written evidence of customer acceptance, when applicable, to verify delivery or performance.
	•	Sales price is fixed or determinable. The Company assesses whether the sales price is fixed or determinable based on the payment terms and whether the sales price is subject to refund or adjustment.
	•	Collectability is reasonably assured. The Company assesses collectability based on creditworthiness of customers as determined by its credit checks, their payment histories, or changes in circumstances that indicate that collectability is not reasonably assured.
	When sales arrangements contain multiple elements the Company allocates revenue to each element based on a selling price hierarchy. The selling price for a deliverable is based on either vendor-specific objective evidence (“VSOE”) if available, third-party evidence (“TPE”) if VSOE is not available, or estimated selling price (“ESP”) if neither VSOE nor TPE is available. The Company then recognizes revenue on each deliverable in accordance with its policies for product and service revenue recognition. VSOE of selling price is based on the price charged when the element is sold separately. In determining VSOE, the Company requires that a substantial majority of the selling prices fall within a reasonable range based on historical discounting trends for specific products and services. TPE of selling price is established by evaluating largely interchangeable competitor products or services in stand-alone sales to similar situated customers. However, as the Company's products contain a significant element of proprietary technology and its solutions offer substantially different features and functionality, the comparable pricing of third-party products with similar functionality typically cannot be obtained and therefore TPE is not used. ESP is established considering multiple factors including, but not limited to pricing practices in different geographies and through different sales channels, gross margin objectives, internal costs, competitor pricing strategies, and industry technology lifecycles.
	In multiple element arrangements where software deliverables are included, revenue is allocated to each separate unit of accounting for each of the non-software deliverables and to the software deliverables as a group using the relative selling prices of each of the deliverables in the arrangement based on the aforementioned selling price hierarchy. If the arrangement contains more than one software deliverable, the arrangement consideration allocated to the software deliverables as a group is then allocated to each software deliverable using the residual method when VSOE of fair value of the undelivered items exists. Under the residual method, the amount of revenue allocated to delivered elements equals the total arrangement consideration less the aggregate fair value of any undelivered elements. If VSOE of one or more undelivered items does not exist, revenue from the entire arrangement is deferred and recognized at the earlier of: (i) delivery of those elements or (ii) when fair value can be established unless maintenance services is the only undelivered element, in which case, the entire arrangement fee is recognized ratably over the maintenance service period.
	The Company limits the amount of revenue recognition for delivered elements to the amount that is not contingent on the future delivery of products or services or subject to customer-specific return or refund privileges.
	The Company records reductions to revenue for estimated product returns and pricing adjustments, such as rebates and price protection, in the same period that the related revenue is recorded. The amount of these reductions is based on historical sales returns and price protection credits, specific criteria outlined in rebate agreements, and other factors known at the time.
	A portion of the Company's sales is made through distributors under agreements allowing for pricing credits or rights of return. As reliable estimates of these credits or returns cannot be made, product revenue on sales made through these distributors is recognized upon sell-through as reported by the distributors to the Company. Deferred revenue on shipments to distributors reflects the effects of distributor pricing credits given and the amount of gross margin expected to be realized upon sell-through. Deferred revenue is recorded net of the related product costs of revenue.
	Service revenues include revenue from maintenance, training, and professional services. Maintenance is offered under renewable contracts. Revenue from maintenance service contracts is deferred and recognized ratably over the contractual support period, which is generally one to three years. Revenue from training and professional services is recognized as services are completed or ratably over the contractual period, which is generally one year or less.
	Allowance for Doubtful Accounts
	The allowance for doubtful accounts is based on the Company's assessment of the collectability of customer accounts. The Company regularly reviews its receivables that remain outstanding past their applicable payment terms and establishes an allowance by considering factors such as historical experience, credit quality, and age of the accounts receivable balances, and current economic conditions that may affect a customer's ability to pay.
	Warranty Reserves
	The Company generally offers a one-year warranty on most of its hardware products, and a 90-day warranty on the media that contains the software embedded in the products. Warranty costs are recognized as part of the Company's cost of sales based on associated material costs, logistics costs, labor costs, and overhead at the time revenue is recognized. Material costs are estimated primarily based upon the historical costs to repair or replace product returns within the warranty period. Labor, logistics and overhead costs are estimated primarily based upon historical trends in the cost to support customer cases within the warranty period.
	Contract Manufacturer Liabilities
	The Company establishes a liability for non-cancelable, non-returnable purchase commitments with its contract manufacturers for carrying charges, quantities in excess of its demand forecasts, or obsolete material charges for components purchased by the contract manufacturers to meet the Company’s demand forecast or customer orders. The demand forecasts are based upon historical trends and analysis from the Company's sales and marketing organizations, adjusted for overall market conditions.
	Research and Development
	Costs to research, design, and develop the Company's products are expensed as incurred.
	Software Development Costs
	Capitalization of software development costs for software to be sold, leased, or otherwise marketed begins when a product's technological feasibility has been established and ends when a product is available for general release to customers. Generally, the Company's products are released soon after technological feasibility has been established. As a result, costs incurred between achieving technological feasibility and product general availability have not been significant.
	The Company capitalizes costs associated with internal-use software systems that have reached the application development stage and are primarily attributable to the Company's enterprise resource planning ("ERP") implementation. Such capitalized costs include external direct costs utilized in developing or obtaining the applications and payroll and payroll-related costs for employees, who are directly associated with the development of the applications.
	Advertising
	Advertising costs are charged to sales and marketing expense as incurred. Advertising expense was $19.2 million, $20.1 million, and $20.0 million, for 2014, 2013, and 2012, respectively.
	Foreign Currency
	Assets and liabilities of foreign operations with non-U.S. Dollar functional currency are translated to U.S. Dollars using exchange rates in effect at the end of the period. Revenue and expenses are translated to U.S. Dollars using average exchange rates for the period. The resulting translation adjustments are included in the Company’s Consolidated Balance Sheets in the stockholders’ equity section as a component of accumulated other comprehensive income. For the Company’s international subsidiaries in which the functional currency is the U.S. dollar, the Company records foreign exchange gains and losses for assets and liabilities denominated in non-US dollar currencies. These remeasurement adjustments are recorded in other income (expense), net in the Consolidated Statements of Operations.
	Loss Contingencies
	The Company is subject to the possibility of various loss contingencies arising in the ordinary course of business. Management considers the likelihood of loss related to an asset, or the incurrence of a liability, as well as its ability to reasonably estimate the amount of loss, in determining loss contingencies. An estimated loss contingency is accrued when it is probable that an asset has been impaired or a liability has been incurred and the amount of loss can be reasonably estimated. The Company regularly evaluates current information available to determine whether such accruals should be adjusted and whether new accruals are required.
Share-Based Compensation
The Company measures and recognizes compensation cost for all share-based awards made to employees and directors, including employee stock options, stock awards, stock units, and employee stock purchases related to the Employee Stock Purchase Plan ("ESPP"). Share-based compensation expense is based on the fair value of the underlying awards and amortized on a straight-line basis, net of estimated forfeitures.
The Company utilizes the Black-Scholes-Merton (“BSM”) option-pricing model to estimate the fair value of its stock options and Employee Stock Purchase Plan ("ESPP") shares. The BSM model requires various highly subjective assumptions that represent management's best estimates of volatility, risk-free interest rate, expected life, and dividend yield. The Company estimates expected volatility based on the implied volatility of market-traded options, on the Company's common stock, adjusted for other relevant factors including historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected life of the Company’s stock options and ESPP. The expected life of a stock option is based on historical experience of employee exercises and post-vesting termination behavior as well as the potential effect from options that have not been exercised. The expected life of ESPP approximates the offering period.
The Company determines the fair value of its restricted stock units ("RSUs"), restricted stock awards ("RSAs"), and performance share awards ("PSAs") based on the closing market price of the Company’s common stock on the date of grant, adjusted by the present value of the expected dividend.
For market-based RSUs, the Company estimates the fair value and derived service period using the Monte Carlo simulation option pricing model ("Monte Carlo model"). The determination of the grant date fair value and derived service periods using the Monte Carlo model is affected by our stock price as well as various highly subjective assumptions that represent management's best estimates of volatility, risk-free interest rate, and dividend yield. The Company estimates expected volatility based on the implied volatility of market-traded options, on the Company's common stock, adjusted for other relevant factors including historical volatility of the Company’s common stock over the contractual life of the Company's market-based RSUs.
Provision for Income Taxes
Deferred tax assets and liabilities are recognized for the expected tax consequences of temporary differences between the tax bases of assets and liabilities and their reported amounts. Valuation allowances are recorded to reduce deferred tax assets to the amount that will more likely than not be realized.
The Company accounts for uncertainty in income taxes using a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon settlement. The Company classifies the liability for unrecognized tax benefits as current to the extent that the Company anticipates payment (or receipt) of cash within one year. Interest and penalties related to uncertain tax positions are recognized in the provision for income taxes.
Concentrations of Risk
Financial instruments that subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, investments, and accounts receivable. The Company invests only in high-quality credit instruments and maintains its cash, cash equivalents and available-for-sale investments in fixed income securities with several high-quality institutions. Deposits held with banks, including those held in foreign branches of global banks, may exceed the amount of insurance provided on such deposits. These deposits may be redeemed upon demand and, therefore, bear minimal credit risk.
The Company’s derivatives expose it to credit risk to the extent that counterparties may be unable to meet the terms of the agreement. To mitigate concentration of risk related to its derivatives, the Company establishes counterparty limits to major credit-worthy financial institutions. In addition, the potential risk of loss with any one counterparty resulting from this type of credit risk is monitored and the derivatives transacted with these entities are relatively short in duration. Therefore, the Company does not expect material losses as a result of defaults by counterparties.
Generally, credit risk with respect to accounts receivable is diversified due to the number of entities comprising the Company's customer base and their dispersion across different geographic locations throughout the world. The Company performs ongoing credit evaluations of its customers and generally does not require collateral on accounts receivable. During the years ended December 31, 2014 and December 31, 2013, no single customer accounted for 10% or more of net revenues. During the year ended December 31, 2012, Verizon Communications, Inc. ("Verizon") accounted for 10.3% of net revenues.
The Company relies on sole suppliers for certain of its components such as application-specific integrated circuits ("ASICs") and custom sheet metal. Additionally, the Company relies primarily on a limited number of significant independent contract manufacturers and outside design manufacturers for the production of its products. The inability of any supplier or manufacturer to fulfill supply requirements of the Company could negatively impact future operating results.
Recent Accounting Pronouncements
In January 2015, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2015-01 (Subtopic 225-20) - Income Statement - Extraordinary and Unusual Items, which eliminates the concept of extraordinary items. ASU 2015-01 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted. The adoption of this standard is not expected to have an impact on the Company's Consolidated Financial Statements.
In December 2014, the FASB issued ASU No. 2014-17 (Topic 805) - Business Combinations, which provides an acquired entity with an option to apply pushdown accounting in its separate financial statements upon occurrence of an event in which an acquirer obtains control of the acquired entity. ASU 2014-17 is effective on November 18, 2014. The adoption of this standard is not expected to have an impact on the Company's Consolidated Financial Statements.
In November 2014, the FASB issued ASU No. 2014-16 (Topic 815) - Derivatives and Hedging, which provides clarification on how current guidance should be interpreted in evaluating the economic characteristics and risks of a host contract in a hybrid financial instrument that is issued in the form of a share. Specifically, the amendments clarify that an entity should consider all relevant terms and features in evaluating the host contract and that no single term or feature would necessarily determine the economic characteristics and risks of the host contract ASU 2014-16 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. The amendment should be applied on a modified retrospective basis to existing hybrid financial instruments issued in the form of a share as of the beginning of the year for which the amendments are effective. Early adoption is permitted. The adoption of this standard is not expected to have a material impact on the Company's Consolidated Financial Statements.
In August 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-15 (Subtopic 205-40) - Presentation of Financial Statements—Going Concern: Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern ("ASU 2014-15") which provides guidance about management's responsibility to evaluate whether or not there is substantial doubt about the Company's ability to continue as a going concern and to provide related footnote disclosure. ASU 2014-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. Early application is permitted. The adoption of this standard is not expected to have an impact on the Company's Consolidated Financial Statements.
In June 2014, the FASB issued ASU No. 2014-12 (Topic 718) - Compensation - Stock Compensation ("ASU 2014-12") which provides guidance that a performance target that affects vesting of a share-based payment and that could be achieved after the requisite service period is a performance condition. As a result, the target is not reflected in the estimation of the award’s grant date fair value. Compensation cost for such an award would be recognized over the required service period, if it is probable that the performance condition will be achieved. ASU 2014-12 is effective for all entities for annual periods beginning after December 15, 2015 and interim periods within those annual periods. ASU 2014-12 should be applied on a prospective basis to awards that are granted or modified on or after the effective date. The adoption of this standard is not expected to have an impact on the Company's Consolidated Financial Statements.
In May 2014, the FASB issued ASU No. 2014-09 (Topic 606)—Revenue from Contracts with Customers ("ASU 2014-09") which provides guidance for revenue recognition. This ASU affects all contracts that the Company enters into with customers to transfer goods and services or for the transfer of nonfinancial assets. This ASU will supersede the revenue recognition requirements in Topic 605, and most industry specific guidance. This ASU also supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition-Construction-Type and Production-Type Contracts. The standard's core principle is that revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. In doing so, the Company will need to use additional judgment and estimates than under the existing guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 is effective for annual and interim periods beginning after December 15, 2016. Early adoption is not permitted. Accordingly, the ASU will be effective for the Company beginning fiscal year 2017. The Company is currently evaluating the impact of the adoption on its Consolidated Financial Statements.
In April 2014, the FASB issued ASU No. 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity ("ASU 2014-08") which raises the threshold for a disposal to qualify as a discontinued operation and requires new disclosures of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. ASU 2014-08 is effective for annual periods beginning on or after December 15, 2014. Early adoption is permitted but only for disposals that have not been reported in financial statements previously issued. The Company has determined that this pronouncement would not have a material impact on the Company's financial position or results of operations.

Business_Combinations_Notes

Business Combinations (Notes)	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Business Combinations	Business Combinations
	The Company's Consolidated Financial Statements include the operating results of acquired businesses from the date of each acquisition. Pro forma results of operations for these acquisitions have not been presented as the financial impact to the Company's consolidated results of operations, both individually and in aggregate, is not material. Additional information, if any, existing as of the acquisition dates but unknown to the Company may become known during the remainder of the measurement period, not to exceed 12 months from the acquisition date, which may result in changes to the amounts and allocations recorded.
	The Company completed one business combination in 2014, one business combination in 2013, and three business combinations in 2012 for cash consideration including the fair value of vested share-based awards assumed, if any, of approximately $28.7 million, $10.0 million, and $187.3 million, respectively.
	The following table presents the purchase consideration allocations for these acquisitions based upon acquisition-date fair values, including cash and cash equivalents acquired (in millions):
		2014 Acquisitions				2013 Acquisitions			2012 Acquisitions
	Net tangible assets acquired	$	—			$	0.1		$	3.5
	Net liabilities acquired	(2.7		)		—			—
	Intangible assets acquired	17.8				9.9			54.1
	Goodwill	13.6				—			129.7
	Total	$	28.7			$	10		$	187.3
	The goodwill recognized for the 2014 and 2012 acquisitions was primarily attributable to expected synergies and was not deductible for U.S. federal income tax purposes.
	2014 Acquisition
	On January 7, 2014, the Company acquired 100% of the equity securities of WANDL, Inc. ("WANDL"), for $28.7 million of cash and stock consideration. WANDL, a provider of software solutions for advanced planning, management, design and optimization of next-generation multi-layer networks, provides the Company with technology and experience in traffic engineering, multi-layer optimization and path computation to help service provider customers optimize the performance and cost of their networks.
	Under the terms of the purchase agreement, the Company assumed share-based awards for employees with a fair value of $34.9 million, which were granted in contemplation of future services and will be expensed as share-based compensation over the remaining service period.
	Intangible Assets Acquired
	The following table presents details of the Company's intangible assets acquired through the business combination completed during the twelve months ended December 31, 2014 (in millions, except years):
		Weighted		Amount
		Average
		Estimated
		Useful
		Life
		(In Years)
	Existing technology	7		$	10.7
	Customer relationships	7		6
	Trade name	4		0.6
	Backlog	1		0.2
	Non-compete agreements	2		0.3
	Total	7		$	17.8
	2013 Acquisition
	During 2013, the Company completed a business combination for approximately $10.0 million in cash consideration of which $0.1 million was allocated to net tangible assets acquired and $9.9 million to intangible assets. Intangible assets acquired consisted of existing technology with a weighted-average estimated useful life of five years.
	2012 Acquisitions
	Contrail
	On December 14, 2012, the Company acquired the remaining ownership interest in Contrail, increasing its ownership from 12% to 100%, in a cash and stock transaction for approximately $91.7 million. Contrail, a privately-held software networking company, provides software-defined networking solutions technology that augments Juniper's portfolio of products and services.
	The aggregate consideration of $91.7 million was allocated as follows: net tangible assets acquired of $3.6 million, including cash and cash equivalents of $8.6 million; intangible assets of $17.4 million; and recognized goodwill of $70.7 million.
	The Company previously accounted for its investment in Contrail at cost, which was $3.0 million prior to the acquisition. As of the acquisition date, the fair value of the Company's previous equity interest in Contrail was remeasured to its fair value of $17.7 million, which was based upon adjustments market participants would consider when estimating the fair value of the previously held interest in Contrail. This resulted in a $14.7 million gain, which was reported within other income (expense), net in the Consolidated Statements of Operations.
	Mykonos Software, Inc.
	On February 13, 2012, the Company acquired 100% of the equity securities of Mykonos Software, Inc. ("Mykonos") for $82.6 million in cash. In connection with this acquisition, the Company acquired net tangible liabilities of $0.2 million, intangible assets of $24.3 million, and recognized goodwill of $58.5 million.
	BitGravity, Inc.
	On March 8, 2012, the Company acquired a source code license and patent joint-ownership related to the service management layer of BitGravity, Inc.'s ("BitGravity") Content Delivery Network ("CDN") technology for $13.0 million in cash. In connection with this acquisition, the Company acquired net tangible assets of $0.1 million, intangible assets of $12.4 million, and recognized goodwill of $0.5 million.
	Intangible Assets Acquired
	The following table presents details of the intangible assets acquired for the business combinations completed during 2012 as of their respective acquisition dates (in millions, except years):
		Contrail						Mykonos			BitGravity
		Weighted		Amount				Weighted	Amount		Weighted	Amount
		Average						Average			Average
		Estimated						Estimated			Estimated
		Useful						Useful			Useful
		Life						Life			Life
		(In Years)						(In Years)			(In Years)
	Existing technology	—		$	—			6	$	19.3	3	$	12.4
	Trade name and trademarks	—		—				7	1		—	—
	In-process research and development	N/A		17.4				N/A	4		—	—
	Total	—		$	17.4			6	$	24.3	3	$	12.4
	Acquired in-process research and development (“IPR&D”) consists of existing research and development projects at the time of the acquisition. Projects that qualify as IPR&D assets represent those that have not yet reached technological feasibility and have no alternative future use. After initial recognition, acquired IPR&D assets are accounted for as indefinite-lived intangible assets. Development costs incurred after acquisition on acquired development projects are expensed as incurred. Upon completion of development, acquired IPR&D assets are considered amortizable intangible assets. If the IPR&D project is abandoned, the related purchased intangible asset is written-off in the period abandoned.

Cash_Equivalents_and_Investmen

Cash Equivalents and Investments (Notes)	12 Months Ended
	Dec. 31, 2014
Cash Equivalents and Investments [Abstract]
Cash Equivalents and Investments	Cash Equivalents and Investments
	Investments in Available-for-Sale and Trading Securities
	The following tables summarize the Company's unrealized gains and losses and fair value of investments designated as available-for-sale and trading securities as of December 31, 2014 and December 31, 2013 (in millions):
		Amortized		Gross Unrealized			Gross Unrealized			Estimated Fair
		Cost		Gains			Losses			Value
	As of December 31, 2014
	Fixed income securities:
	Asset-backed securities	$	269.3	$	—		$	(0.3	)	$	269
	Certificates of deposit	10.6		—			—			10.6
	Commercial paper	20.3		—			—			20.3
	Corporate debt securities	738.6		0.5			(1.1		)	738
	Foreign government debt securities	24.6		—			—			24.6
	Government-sponsored enterprise obligations	162.2		—			(0.1		)	162.1
	U.S. government securities	246.1		—			(0.1		)	246
	Total fixed income securities	1,471.70		0.5			(1.6		)	1,470.60
	Money market funds	594.2		—			—			594.2
	Mutual funds	3.9		0.1			—			4
	Publicly-traded equity securities	2.1		—			(0.1		)	2
	Total available-for-sale securities	2,071.90		0.6			(1.7		)	2,070.80
	Trading securities in mutual funds(1)	16.3		—			—			16.3
	Total	$	2,088.20	$	0.6		$	(1.7	)	$	2,087.10
	Reported as:
	Cash equivalents	$	576.6	$	—		$	—		$	576.6
	Restricted investments	45.2		—			—			45.2
	Short-term investments	332.2		0.2			(0.2		)	332.2
	Long-term investments	1,134.20		0.4			(1.5		)	1,133.10
	Total	$	2,088.20	$	0.6		$	(1.7	)	$	2,087.10
	________________________________
	-1	Balance includes the Company's non-qualified deferred compensation plan assets.
		Amortized		Gross Unrealized			Gross Unrealized			Estimated Fair
		Cost		Gains			Losses			Value
	As of December 31, 2013
	Fixed income securities:
	Asset-backed securities	$	249.9	$	0.1		$	(0.1	)	$	249.9
	Certificates of deposit	27.6		—			—			27.6
	Commercial paper	6.9		—			—			6.9
	Corporate debt securities	813.6		2			(0.3		)	815.3
	Foreign government debt securities	10.7		—			—			10.7
	Government-sponsored enterprise obligations	306.2		0.1			(0.1		)	306.2
	U.S. government securities	303.3		0.1			(0.1		)	303.3
	Total fixed income securities	1,718.20		2.3			(0.6		)	1,719.90
	Money market funds	1,043.70		—			—			1,043.70
	Mutual funds	3.9		0.1			—			4
	Publicly-traded equity securities	12		104.5			(1.9		)	114.6
	Total available-for-sale securities	2,777.80		106.9			(2.5		)	2,882.20
	Trading securities in mutual funds(1)	15.4		—			—			15.4
	Total	$	2,793.20	$	106.9		$	(2.5	)	$	2,897.60
	Reported as:
	Cash equivalents	$	996.2	$	—		$	—		$	996.2
	Restricted investments	87.5		0.1			—			87.6
	Short-term investments	459		104.9			(2.0		)	561.9
	Long-term investments	1,250.50		1.9			(0.5		)	1,251.90
	Total	$	2,793.20	$	106.9		$	(2.5	)	$	2,897.60
	_______________________________
	-1	Balance includes the Company's non-qualified deferred compensation plan assets.
	The following table presents the contractual maturities of the Company's total fixed income securities as of December 31, 2014 (in millions):
		Amortized		Gross Unrealized			Gross Unrealized			Estimated Fair
		Cost		Gains			Losses			Value
	Due in less than one year	$	337.5	$	0.1		$	(0.2	)	$	337.4
	Due between one and five years	1,134.20		0.4			(1.4		)	1,133.20
	Total	$	1,471.70	$	0.5		$	(1.6	)	$	1,470.60
	The Company had 437 and 178 investments in unrealized loss positions as of December 31, 2014 and December 31, 2013, respectively. The gross unrealized losses related to these investments were primarily due to changes in market interest rates and stock prices. The Company periodically reviews its investments to identify and evaluate investments that have an indication of possible impairment. The Company aggregates its investments by category and length of time the securities have been in a continuous unrealized loss position to facilitate its evaluation.
	For available-for-sale debt securities that have unrealized losses, the Company evaluates whether (i) it has the intention to sell any of these investments and (ii) whether it is not 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 December 31, 2014, 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 year ended December 31, 2014, 2013, and 2012.
	For available-for-sale equity securities that have unrealized losses, the Company evaluates whether there is an indication of other-than-temporary impairments. This determination is based on several factors, including the financial condition and near-term prospects of the issuer and the Company’s intent and ability to hold the publicly-traded equity securities for a period of time sufficient to allow for any anticipated recovery in market value. During the year ended December 31, 2014, the Company determined that certain available-for-sale equity securities were other-than temporarily impaired, resulting in an impairment charge of $1.1 million that was recorded within other income (expense), net, in the Consolidated Statement of Operations. During the years ended December 31, 2013 and December 31, 2012 the Company did not recognize other-than-temporary impairments associated with these investments.
During the year ended December 31, 2014, gross realized gains from available-for-sale securities were $166.8 million and gross realized losses were not material, excluding the impairment charge noted above. There were no material gross realized gains or losses from trading securities during the year ended December 31, 2014, and there were no material gross realized gains or losses from available-for-sale and trading securities during the years ended December 31, 2013, and December 31, 2012.
The following tables present the Company's available-for-sale securities that were in an unrealized loss position as of December 31, 2014 and December 31, 2013 (in millions):
	Less than 12 Months					12 Months or Greater					Total
	Fair		Unrealized			Fair			Unrealized		Fair		Unrealized
	Value		Loss			Value			Loss		Value		Loss
As of December 31, 2014
Fixed income securities:
Asset-backed securities	$	221.9	$	(0.3	)	$	—		$	—	$	221.9	$	(0.3	)
Corporate debt securities	515.9		(1.1		)	—			—		515.9		(1.1		)
Foreign government debt securities(1)	24.6		—			—			—		24.6		—
Government-sponsored enterprise obligations	113.8		(0.1		)	—			—		113.8		(0.1		)
U.S. government securities	189		(0.1		)	—			—		189		(0.1		)
Total fixed income securities	1,065.20		(1.6		)	—			—		1,065.20		(1.6		)
Publicly-traded equity securities	2		(0.1		)	—			—		2		(0.1		)
Total available-for sale securities	$	1,067.20	$	(1.7	)	$	—		$	—	$	1,067.20	$	(1.7	)
________________________________
(1) Balances less than 12 months include investments that were in an immaterial unrealized loss position as of December 31, 2014.
	Less than 12 Months					12 Months or Greater					Total
	Fair		Unrealized			Fair			Unrealized		Fair		Unrealized
	Value		Loss			Value			Loss		Value		Loss
As of December 31, 2013
Fixed income securities:
Asset-backed securities(1)	$	153	$	(0.1	)	$	0.6		$	—	$	153.6	$	(0.1	)
Corporate debt securities(1)	156.1		(0.3		)	9.7			—		165.8		(0.3		)
Foreign government debt securities(2)	10		—			—			—		10		—
Government-sponsored enterprise obligations	123.1		(0.1		)	—			—		123.1		(0.1		)
U.S. government securities	119.7		(0.1		)	—			—		119.7		(0.1		)
Total fixed income securities	561.9		(0.6		)	10.3			—		572.2		(0.6		)
Publicly-traded equity securities	6.8		(1.9		)	—			—		6.8		(1.9		)
Total available-for-sale securities	$	568.7	$	(2.5	)	$	10.3		$	—	$	579	$	(2.5	)
________________________________
(1)	Balances 12 months or greater include investments that were in an immaterial unrealized loss position as of December 31, 2013.
(2)	Balances less than 12 months include investments that were in an immaterial unrealized loss position as of December 31, 2013.
Restricted Cash and Investments
The Company classifies certain cash and investments as restricted cash and investments on its Consolidated Balance Sheets for: (i) amounts held in escrow accounts, as required in connection with certain acquisitions completed between 2005 and 2014; (ii) the India Gratuity Trust and Israel Retirement Trust, which cover statutory severance obligations in the event of termination of any of the Company's India and Israel employees, respectively; and (iii) the Directors and Officers indemnification trust ("D&O Trust"). The restricted investments are designated as available-for-sale securities.
Privately-Held Investments
As of December 31, 2014 and December 31, 2013, the carrying values of the Company's privately-held investments of $89.9 million and $57.2 million, respectively, were included in other long-term assets in the Consolidated Balance Sheets. As of December 31, 2014, the carrying value of the privately-held investments includes debt and redeemable preferred stock securities of $47.5 million. For the year ended December 31, 2014, the Company recorded $15.0 million in other comprehensive income for unrealized gains associated with its privately-held debt securities. During the year ended December 31, 2013, there were $102.7 million unrealized gains associated with its privately-held securities in other comprehensive income.
The Company reviews its investments to identify and evaluate investments that have an indication of possible impairment. The Company adjusts the carrying value for its privately-held investments for any impairment if the fair value is less than the carrying value of the respective assets on an other-than-temporary basis.
During the years ended December 31, 2014, 2013, and 2012, the Company determined that certain privately-held investments were other-than-temporarily impaired, resulting in impairment charges of $1.1 million, $2.8 million, and $20.0 million, respectively, that were recorded within other income (expense), net in the Consolidated Statements of Operations.

Fair_Value_Measurements_Notes

Fair Value Measurements (Notes)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements
	Assets and Liabilities Measured at Fair Value on a Recurring Basis
	The following tables provide a summary of assets and liabilities measured at fair value on a recurring basis and as reported in the Consolidated Balance Sheets (in millions):
		Fair Value Measurements at December 31, 2014 Using:
		Quoted Prices in		Significant Other			Significant Other
		Active Markets For		Observable			Unobservable
		Identical Assets		Remaining Inputs			Remaining Inputs
		(Level 1)		(Level 2)			(Level 3)		Total
	Assets measured at fair value:
	Available-for-sale securities:
	Asset-backed securities	$	—	$	269		$	—	$	269
	Certificates of deposit	—		10.6			—		10.6
	Commercial paper	—		20.3			—		20.3
	Corporate debt securities	—		738			—		738
	Foreign government debt securities	—		24.6			—		24.6
	Government-sponsored enterprise obligations	—		162.1			—		162.1
	Money market funds (1)	594.2		—			—		594.2
	Mutual funds (2)	4		—			—		4
	Publicly-traded equity securities	2		—			—		2
	U.S. government securities	246		—			—		246
	Total available-for-sale securities	846.2		1,224.60			—		2,070.80
	Trading securities in mutual funds (3)	16.3		—			—		16.3
	Privately-held debt securities	—		—			47.5		47.5
	Derivative assets:
	Foreign exchange contracts	—		0.1			—		0.1
	Total assets measured at fair value	$	862.5	$	1,224.70		$	47.5	$	2,134.70
	Liabilities measured at fair value:
	Derivative liabilities:
	Foreign exchange contracts	$	—	$	(3.9	)	$	—	$	(3.9	)
	Total liabilities measured at fair value	$	—	$	(3.9	)	$	—	$	(3.9	)
	Total assets measured at fair value, reported as:
	Cash equivalents	$	552.9	$	23.7		$	—	$	576.6
	Restricted investments	45.2		—			—		45.2
	Short-term investments	87		245.2			—		332.2
	Long-term investments	177.4		955.7			—		1,133.10
	Prepaid expenses and other current assets	—		0.1			—		0.1
	Other long-term assets	—		—			47.5		47.5
	Total assets measured at fair value	$	862.5	$	1,224.70		$	47.5	$	2,134.70
	Total liabilities measured at fair value, reported as:
	Other accrued liabilities	$	—	$	(3.9	)	$	—	$	(3.9	)
	Total liabilities measured at fair value	$	—	$	(3.9	)	$	—	$	(3.9	)
	________________________________
	(1)	Balance includes $41.3 million of restricted investments measured at fair market value, related to the Company's D&O trust and acquisitions related escrows.
	(2)	Balance relates to the restricted investments measured at fair market value of the Company's India Gratuity Trust.
	(3)	Balance relates to the investments measured at fair value related to the Company's non-qualified deferred compensation plan assets.
		Fair Value Measurements at December 31, 2013 Using:
		Quoted Prices in		Significant Other			Significant Other
		Active Markets For		Observable			Unobservable
		Identical Assets		Remaining Inputs			Remaining Inputs
		(Level 1)		(Level 2)			(Level 3)		Total
	Assets measured at fair value:
	Available-for-sale securities:
	Asset-backed securities	$	—	$	249.9		$	—	$	249.9
	Certificates of deposit	—		27.6			—		27.6
	Commercial paper	—		6.9			—		6.9
	Corporate debt securities	—		815.3			—		815.3
	Foreign government debt securities	—		10.7			—		10.7
	Government-sponsored enterprise obligations	—		306.2			—		306.2
	Money market funds (1)	1,043.70		—			—		1,043.70
	Mutual funds (2)	4		—			—		4
	Publicly-traded equity securities	114.6		—			—		114.6
	U.S. government securities	197.2		106.1			—		303.3
	Total available-for-sale securities	1,359.50		1,522.70			—		2,882.20
	Trading securities in mutual funds (3)	15.4		—			—		15.4
Privately-held debt securities	—		—			28.1		28.1
Derivative assets:
Foreign exchange contracts	—		3			—		3
Total assets measured at fair value	$	1,374.90	$	1,525.70		$	28.1	$	2,928.70
Liabilities measured at fair value:
Derivative liabilities:
Foreign exchange contracts	$	—	$	(0.7	)	$	—	$	(0.7	)
Total liabilities measured at fair value	$	—	$	(0.7	)	$	—	$	(0.7	)
Total assets measured at fair value, reported as:
Cash equivalents	$	965.1	$	31.1		$	—	$	996.2
Restricted investments	87.6		—			—		87.6
Short-term investments	246.5		315.4			—		561.9
Long-term investments	75.7		1,176.20			—		1,251.90
Prepaid expenses and other current assets	—		3			—		3
Other long-term assets	—		—			28.1		28.1
Total assets measured at fair value	$	1,374.90	$	1,525.70		$	28.1	$	2,928.70
Total liabilities measured at fair value, reported as:
Other accrued liabilities	$	—	$	(0.7	)	$	—	$	(0.7	)
Total liabilities measured at fair value	$	—	$	(0.7	)	$	—	$	(0.7	)
_______________________________
(1)	Balance includes $83.6 million of restricted investments measured at fair market value, related to the Company's D&O trust and acquisition related escrows.
(2)	Balance relates to the restricted investments measured at fair market value of the Company's India Gratuity Trust.
(3)	Balance relates to the investments measured at fair value related to the Company's non-qualified deferred compensation plan assets.
The Company's Level 2 available-for-sale fixed income securities are priced using quoted market prices for similar instruments or non-binding market prices that are corroborated by observable market data. The Company uses inputs such as actual trade data, benchmark yields, broker/dealer quotes, or alternative pricing sources with reasonable levels of price transparency which are obtained from quoted market prices, independent pricing vendors, or other sources, to determine the ultimate fair value of these assets. The Company's derivative instruments are classified as Level 2, as they are not actively traded and are valued using pricing models that use observable market inputs. The Company's policy is to recognize asset or liability transfers among Level 1, Level 2, and Level 3 at the beginning of the quarter in which a change in circumstances resulted in a transfer. During the year ended December 31, 2014, the Company had no transfers between levels of the fair value hierarchy of its assets or liabilities measured at fair value. During the year ended December 31, 2013, the Company transferred approximately $287.4 million of government agency bonds within government sponsored enterprise obligations from Level 1 to Level 2 primarily due to the use of additional valuation inputs more appropriately classified as Level 2 inputs. During the year ended December 31, 2013, the Company had no transfers to Level 3.
All of the Company's privately-held debt securities are classified as Level 3 assets due to the absence of quoted market prices and an inherent lack of liquidity. The Company estimates the fair value of its privately-held debt investments on a recurring basis using an analysis of the financial condition and near-term prospects of the investee, including recent financing activities and the investee's capital structure. During the year ended December 31, 2014, there were purchases of $5.0 million related to privately-held debt securities.
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis
Certain of the Company's assets, including intangible assets, goodwill, and privately-held equity investments, are measured at fair value on a nonrecurring basis, only if impairment is indicated. Privately-held equity investments, which are normally carried at cost, are measured at fair value on a nonrecurring basis due to events and circumstances that the Company identified as significantly impacting the fair value of investments. The Company estimates the fair value of its privately-held equity investments using an analysis of the financial condition and near-term prospects of the investee, including recent financing activities and the investee's capital structure.
As of December 31, 2014, the Company recorded a goodwill impairment charge of $850.0 million for its Security reporting unit measured at fair value on a nonrecurring basis. The remeasurement of goodwill is classified as Level 3 value assessment due to the significance of unobservable inputs developed using company-specific information. Refer to Note 7 Goodwill and Purchased Intangible Assets for further information on the goodwill impairment charge and the unobservable inputs used.
As of December 31, 2014, the Company had no significant privately-held equity investments measured at fair value on a nonrecurring basis. As of December 31, 2013, the Company had $2.0 million of privately-held equity investments measured at fair value on a nonrecurring basis and were classified as Level 3 assets due to the absence of quoted market prices and inherent lack of liquidity. The impairment charges of $2.8 million, representing the difference between the net book value and the fair value, are recorded to other income (expense), net in the Consolidated Statements of Operations.
As of December 31, 2012, certain purchased intangible assets with a carrying value of $5.4 million, were impaired and were written-down to their fair value of zero. The impairment charge of $5.4 million was recorded within cost of revenues on the Consolidated Statement of Operations and was classified as Level 3. The Company measured the fair value of these assets primarily using discounted cash flow projections. As of December 31, 2014, the Company had no impairments associated with purchased intangible assets.
As of December 31, 2014 and 2013, the Company had no liabilities measured at fair value on a nonrecurring basis.
Assets and Liabilities Not Measured at Fair Value
The carrying amounts of the Company's accounts receivable, financing receivables, accounts payable, and other accrued liabilities approximate fair value due to their short maturities. As of December 31, 2014, the estimated fair value of the Company's promissory note in connection with the sale of Junos Pulse recorded in other long term assets in the Consolidated Balance Sheet was $125.0 million classified as Level 3 assets due to the absence of quoted market prices and inherent lack of liquidity. As of December 31, 2014 and December 31, 2013, the estimated fair value of the Company's long-term debt in the Consolidated Balance Sheets was approximately $1,395.2 million and $1,023.5 million, respectively, based on observable market inputs (Level 2).

Derivative_Instruments_Notes

Derivative Instruments (Notes)	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments
	The Company uses derivatives to partially offset its market exposure to fluctuations in certain foreign currencies and does not enter into derivatives for speculative or trading purposes.
	The notional amount of the Company's foreign currency derivatives are summarized as follows (in millions):
		As of December 31,
		2014		2013
	Cash flow hedges	$	160.7	$	137.6
	Non-designated derivatives	78		144.4
	Total	$	238.7	$	282
	Cash Flow Hedges
	The Company uses foreign currency forward or option contracts to hedge the Company's planned cost of services and operating expenses denominated in foreign currencies. These derivatives are designated as cash flow hedges. Execution of these cash flow hedge derivatives typically occurs every month with maturities of one year or less.
	See Note 5, Fair Value Measurements, for the fair values of the Company’s derivative instruments in the Consolidated Balance Sheets.
	As of December 31, 2014, the Company recognized a loss of $3.4 million in accumulated other comprehensive (loss) income for the effective portion of its derivative instruments and reclassified a gain of $3.4 million during the year ended December 31, 2014 from other comprehensive income to operating expense in the Consolidated Statements of Operations. As of December 31, 2013, the Company recognized a loss of $1.0 million in accumulated other comprehensive income for the effective portion of its derivative instruments and reclassified a gain of $0.7 million during the year ended December 31, 2013 from other comprehensive income to operating expense in the Consolidated Statements of Operations. As of December 31, 2012, the Company recognized a gain of $7.2 million in accumulated other comprehensive income for the effective portion of its derivative instruments and reclassified a loss of $7.5 million during the year ended December 31, 2012 from other comprehensive income to operating expense in the Consolidated Statements of Operations.
	The ineffective portion of the Company's derivative instruments recognized in its Consolidated Statements of Operations was not material during the years ended December 31, 2014, 2013, and 2012.
	Non-Designated Derivatives
	During the years ended December 31, 2014, 2013, and 2012, the Company recognized a net loss of $2.4 million, a net gain of $0.9 million, and a gain of $1.0 million, respectively, on non-designated derivative instruments within other income (expense), net, in its Consolidated Statements of Operations.
	Offsetting of Derivatives
	The Company presents its derivative assets and derivative liabilities on a gross basis in the Consolidated Balance Sheets. However, under agreements containing provisions on netting with certain counterparties of foreign exchange contracts, subject to applicable requirements, the Company is allowed to net-settle transactions on the same date in the same currency, with a single net amount payable by one party to the other. As of December 31, 2014 and December 31, 2013, the potential effect of rights of setoff associated with derivative instruments was not material. The Company is neither required to pledge nor entitled to receive cash collateral related to these derivative transactions.

Goodwill_and_Purchased_Intangi

Goodwill and Purchased Intangible Assets (Notes)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Purchased Intangible Assets	Goodwill and Purchased Intangible Assets
	Goodwill
	The following table presents the goodwill activity (in millions):
		Total
	December 31, 2012	$	4,057.80
	Foreign currency translation adjustment	(0.1		)
	December 31, 2013	4,057.70
	Additions due to business combination	13.6
	Impairment	(850.0		)
	Divestiture	(239.8		)
	31-Dec-14	$	2,981.50
	In the fourth quarter of 2014, the Company performed its annual goodwill impairment test for the Company's three reporting units: Routing, Switching, and Security. The Company compared each reporting units’ fair value to their current value to determine whether an impairment exists. The fair value was determined by using a combination of the income approach and the market approach.
	Under the income approach, the fair value of each reporting unit was based on the present value of the estimated future cash flows that the reporting unit is expected to generate over its remaining life. Cash flow projections were based on management's estimates of revenue growth rates and operating margins, taking into consideration industry and market conditions. The discount rates used were based on the weighted-average cost of capital adjusted for the relevant risk associated with business-specific characteristics and the uncertainty related to the reporting unit’s ability to execute on the projected cash flows. Under the market approach, the Company estimated the fair value based on market multiples of revenue and earnings derived from comparable publicly-traded companies with similar operating and investment characteristics as the reporting units. The income approach and the market approach were equally weighted to derive the fair value of each reporting unit.
	The fair value of the Company’s Routing and Switching reporting units significantly exceeded their carrying value. However the fair value of the Security reporting unit did not exceed its carrying value and therefore the Company determined the Security reporting unit’s goodwill was impaired. In 2014, the Company re-aligned its go-to-market and research and development resources on projects with the highest potential for growth and continued to leverage its engineering efforts across its Routing, Switching, and Security products. In the fourth quarter of 2014, the Company began to implement a new Security strategy focused on network resiliency and performance based on the SRX platform. As a result, the Company rationalized its Security product portfolio including developing a new product roadmap and exiting certain point products, including the divestiture of Junos Pulse. These factors decreased the Company's short term and near term revenue and profitability forecasts of the Security reporting unit.
	In determining the impairment amount, the fair value of the Security reporting unit was allocated to its assets and liabilities, including any unrecognized intangible assets, based on their respective fair values. Assumptions used in measuring the value of these assets and liabilities included the discount rates, customer renewal rates, and technology obsolescence rates used in valuing the intangible assets, and pricing of comparable transactions in the market in valuing the tangible assets. Based on this allocation, the Security reporting unit's carrying value of goodwill exceeded the implied fair value of goodwill, resulting in a goodwill impairment charge of $850.0 million which was recorded in the Consolidated Statement of Operations.
	There were no impairments to goodwill during the years ended December 31, 2013, and 2012.
	Purchased Intangible Assets
	The Company’s purchased intangible assets were as follows (in millions):
		Gross			Accumulated			Impairments and			Net
					Amortization			Other Charges
	As of December 31, 2014
	Intangible assets with finite lives:
	Technologies and patents	$	567.7		$	(466.1	)	$	(49.9	)	$	51.7
	Customer contracts, support agreements, and	78.1			(65.2		)	(2.8		)	10.1
	related relationships
	Other	1.1			(0.5		)	—			0.6
	Total purchased intangible assets	$	646.9		$	(531.8	)	$	(52.7	)	$	62.4
	As of December 31, 2013
	Intangible assets with finite lives:
	Technologies and patents	$	581.4		$	(453.4	)	$	(30.5	)	$	97.5
	Customer contracts, support agreements, and	74.3			(62.7		)	(2.2		)	9.4
	related relationships
	Total purchased intangible assets	$	655.7		$	(516.1	)	$	(32.7	)	$	106.9
	The following table presents the amortization of intangible assets included in the Consolidated Statements of Operations (in millions):
		Years Ended December 31,
		2014			2013			2012
	Cost of revenues	$	30.9		$	27.3		$	27.6
	Operating expenses:
	Sales and marketing	4.2			3.4			3.5
	General and administrative	1.2			1.2			1.2
	Total operating expenses	5.4			4.6			4.7
	Total	$	36.3		$	31.9		$	32.3
	In connection with the restructuring plan in 2014 and 2012 discussed in Note 9, Restructuring and Other Charges, the Company determined certain intangible assets of $20.0 million and $10.7 million, respectively, were no longer utilized. Additionally, in 2012 the Company recorded a $5.4 million impairment charge as a result of the fair value assessment. During the year ended December 31, 2014, the Company recorded charges of $19.3 million in cost of revenues and $0.7 million in restructuring and other charges in the Consolidated Statements of Operations. During the year ended December 31, 2012, the Company recorded charges of $16.1 million in cost of revenues in the Consolidated Statements of Operations. There were no impairment charges to purchased intangible assets during the years ended December 31, 2013.
	As of December 31, 2014, the estimated future amortization expense of purchased intangible assets with finite lives is as follows (in millions):
	Years Ending December 31,	Amount
	2015	$	24.2
	2016	13.8
	2017	8.9
	2018	5.2
	2019	4.9
	Thereafter	5.4
	Total	$	62.4

Other_Financial_Information_No

Other Financial Information (Notes)	12 Months Ended
	Dec. 31, 2014
Other Financial Information [Abstract]
Other Financial Information	Other Financial Information
	Inventories
	The Company purchases and holds inventory to provide adequate component supplies over the life of the underlying products. The majority of the Company's inventory is production components to be used in the manufacturing process and finished goods inventory in transit. Inventories are reported within prepaid expenses and other current assets and other long-term assets in the Consolidated Balance Sheets. Total inventories consisted of the following (in millions):
		As of December 31,
		2014			2013
	Production materials	$	38.3		$	51.3
	Finished goods	24.2			1.4
	Inventories	$	62.5		$	52.7
	During the year ended December 31, 2014, the Company recorded $15.5 million to cost of revenues, related to the acceleration of the end-of-life of certain products in connection with the 2014 Restructuring Plan discussed in Note 9, Restructuring and Other Charges. There were no such charges during the year ended December 31, 2013.
	During the year ended December 31, 2012, the Company recorded charges of $44.3 million, to cost of revenues, representing inventory held in excess of forecasted demand, of which $36.3 million was in connection with the restructuring plan in 2012 discussed in Note 9, Restructuring and Other Charges.
	Property and Equipment, Net
	Property and equipment, net, consisted of the following (in millions):
		As of December 31,
		2014			2013
	Computers and equipment	$	806.1		$	794.6
	Software	161.2			108.4
	Leasehold improvements	179.5			202.6
	Furniture and fixtures	33.7			42.5
	Building and building improvements	238.4			242.6
	Land and land improvements	241			238.9
	Construction-in-process	70.3			79.5
	Property and equipment, gross	1,730.20			1,709.10
	Accumulated depreciation	(825.9		)	(826.8		)
	Property and equipment, net	$	904.3		$	882.3
	Depreciation expense was $141.9 million, $148.2 million, and $154.7 million in 2014, 2013, and 2012, respectively. Property and equipment is periodically reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.
	Other Long-Term Assets
	Other long-term assets consisted of the following (in millions):
		As of December 31,
		2014			2013
	Privately-held investments	$	89.9		$	57.2
	Licensed software	8.6			90.4
	Federal income tax receivable	20			20
	Customer financing receivable	16.9			19.9
	Inventory	8			15.2
	Prepaid costs, deposits, and other	35.5			31.1
	Promissory note in connection with the sale of Junos Pulse(1)	125			—
	Other long-term assets	$	303.9		$	233.8
	_______________________________
	(1)	Refer to Other Income (Expense), net below for further information on the promissory note.
	In connection with the 2014 Restructuring Plan discussed in Note 9, Restructuring and Other Charges, the Company reviewed its product portfolio and determined to cease development of the application delivery controller software technology licensed in July 2012 as well as development of another technology, for which the Company has a prepaid license. As a result, the Company recognized a total charge of $85.4 million recorded within operating expenses in the Consolidated Statements of Operations during the year ended December 31, 2014. There were no revenues associated with this technology.
	Warranties
	The Company accrues for warranty costs based on associated material, labor for customer support, and overhead at the time revenue is recognized. This accrual is reported as accrued warranty within current liabilities in the Consolidated Balance Sheets. Changes in the Company’s warranty reserve were as follows (in millions):
		As of December 31,
		2014			2013
	Beginning balance	$	28		$	29.7
	Provisions made during the period, net	28.6			28.8
	Adjustments related to pre-existing warranties	—			(2.1		)
	Actual costs incurred during the period	(27.9		)	(28.4		)
	Ending balance	$	28.7		$	28
	Deferred Revenue
	Details of the Company's deferred revenue, as reported in the Consolidated Balance Sheets, were as follows (in millions):
		As of December 31,
		2014			2013
	Deferred product revenue:
	Undelivered product commitments and other product deferrals	$	180.3		$	184.9
	Distributor inventory and other sell-through items	103.7			118.7
	Deferred gross product revenue	284			303.6
	Deferred cost of product revenue	(58.4		)	(58.6		)
	Deferred product revenue, net	225.6			245
	Deferred service revenue	850.1			824.3
	Total	$	1,075.70		$	1,069.30
	Reported as:
	Current	$	780.8		$	705.8
	Long-term	294.9			363.5
Total	$	1,075.70		$	1,069.30
Deferred product revenue represents unrecognized revenue related to shipments to distributors that have not sold through to end-users, undelivered product commitments, and other shipments that have not met all revenue recognition criteria. Deferred product revenue is recorded net of the related costs of product revenue. Deferred service revenue represents billable amounts for service contracts, which include technical support, hardware and software maintenance, professional services, and training, for which services have not been rendered.
Other Income (Expense), Net
Other income (expense), net consisted of the following (in millions):
	Years Ended December 31,
	2014			2013			2012
Interest income	$	10		$	8.7		$	11
Interest expense	(66.9		)	(58.4		)	(52.9		)
Net gain on legal settlement	196.1			—			—
Gain on investments	167.9			11.3			26.7
Gain on sale of Junos Pulse	19.6			—			—
Other	6.7			(2.0		)	(1.4		)
Other income (expense), net	$	333.4		$	(40.4	)	$	(16.6	)
Interest income primarily includes interest earned on the Company’s cash, cash equivalents, and investments. Interest expense primarily includes interest, net of capitalized interest expense, from long-term debt and customer financing arrangements. Other typically consists of investment and foreign exchange gains and losses and other non-operational income and expense items.
Interest Expense
For the years ended December 31, 2014, 2013 and 2012, interest expense included $57.5 million, net of $2.7 million capitalized, $45.2 million, net of $1.9 million capitalized, and $40.0 million, net of $7.1 million capitalized, respectively, related to the Company's outstanding long-term debt issued in March 2011 and in February 2014 discussed in Note 10, Long-Term Debt and Financing.
Gain on Legal Settlement
During the year ended December 31, 2014, the Company entered into a settlement agreement with Palo Alto Networks, Inc. ("PAN") resolving a patent litigation between the two companies, which resulted in a realized gain on legal settlement and subsequent sale of related securities of $196.1 million, net of legal fees.
Gain on Investments
During the year ended December 31, 2014, the Company recorded a gain of $163.0 million, primarily related to the sale of investments which were converted from privately-held investments to publicly-traded equity upon IPO and subsequently sold.
During the year ended December 31, 2013, net gain on investments was primarily comprised of a gain of $7.1 million related to the Company's privately-held investments.
Gain on Sale of Junos Pulse
On October 1, 2014, the Company completed the sale of its Junos Pulse product portfolio. The Company received total consideration of $230.7 million, of which $105.7 million was in cash, net of a $19.3 million working capital adjustment, and $125.0 million was in the form of an 18-month non-contingent interest bearing promissory note issued to the Company. As a result of the sale, the Company recorded a gain of $19.6 million in other income (expense), net in the Consolidated Statement of Operations. The Company's sale of Junos Pulse is driven by product rationalization in connection with the Company's initiative to focus on projects with the highest potential for growth.

Restructuring_and_Other_Charge

Restructuring and Other Charges (Notes)	12 Months Ended
	Dec. 31, 2014
Restructuring and Related Activities [Abstract]
Restructuring and Other Charges	Restructuring and Other Charges
	The following table presents restructuring and other charges included in cost of revenues and restructuring and other charges in the Consolidated Statements of Operations under the Company's restructuring plans (in millions):
		Years Ended December 31,
		2014		2013		2012
	Severance	$	52.6	$	22.9	$	36.7
	Facilities	14.4		10		5.8
	Contract terminations and other	2.3		14.6		57.2
	Asset impairments and write-downs	139.2		—		—
	Total	$	208.5	$	47.5	$	99.7
	Reported as:
	Cost of revenues	$	41.5	$	8.4	$	52.9
	Restructuring and other charges	167		39.1		46.8
	Total	$	208.5	$	47.5	$	99.7
	Restructuring and other charges noted above are based on the Company's 2014 Restructuring Plan and Other Restructuring Plans that were committed to by management. Any changes in the estimates of executing the approved plans are reflected in the Company's results of operations.
	2014 Restructuring Plan
	In the first quarter of 2014, the Company initiated a restructuring plan (the “2014 Restructuring Plan”) designed to refocus the Company's strategy, optimize its structure, and improve operational efficiencies. The 2014 Restructuring Plan consists of workforce reductions, facility consolidations and closures, asset write-downs, contract terminations and other charges.
	During the year ended December 31, 2014, the Company recorded $52.0 million of severance costs, $14.2 million of facility consolidation and closures costs, $85.4 million of impairment charges related to licensed software, $12.3 million of asset write-downs, and $2.3 million of charges related to contract terminations, which were recorded to restructuring and other charges in the Consolidated Statements of Operations. In connection with the facility consolidation and closures charge of $14.2 million, the Company, with the consent of its landlord and the administrative agent for the holder of certain liens secured upon the buildings on the leased premises, assigned certain of its real property leases, totaling approximately 0.4 million square feet, to a third party. Concurrently with the assignments, the Company executed a sublease with the assignee for one of the properties of approximately 0.1 million square feet, for a period of two years, with one-time right to extend the term for up to six months. Under these arrangements, the Company paid $12.3 million to the landlord and was released from all future lease obligations following the date of the assignments. The Company also incurred $5.3 million of transaction fees, which were recorded to restructuring and other charges in the Consolidated Statements of Operations. Offsetting these charges was an adjustment relating to deferred rent liability relating to these premises of $9.8 million.
	The Company also recorded inventory write-downs of $15.5 million, intangibles write-downs of $19.3 million, and a charge related to products with contract manufacturers of $6.7 million for acceleration of the end-of-service life of certain products to cost of revenues in the Consolidated Statements of Operations during the year ended December 31, 2014.
	The 2014 Restructuring Plan has been substantially completed as of December 31, 2014, and the Company does not expect to record significant future charges under this restructuring plan.
	2013 Restructuring Plan
	During 2013, the Company initiated a restructuring plan (the "2013 Restructuring Plan") to continue to improve its cost structure and rationalize its product portfolio and rebalance its investments. The 2013 Restructuring Plan consists of workforce reductions, contract terminations, and project cancellations. The Company recorded $0.6 million in severance costs related to the 2013 Restructuring Plan during the year ended December 31, 2014. Under the 2013 Restructuring Plan, total costs incurred through December 31, 2014 were $28.9 million, of which $3.3 million was recorded within cost of revenues and $25.6 million was recorded within restructuring and other charges in the Consolidated Statements of Operations. The restructuring activities related to this plan are substantially complete, and the Company does not expect to record significant future charges under this plan.
	2012 Restructuring Plan
	During 2012, the Company initiated a restructuring plan (the "2012 Restructuring Plan") to bring its cost structure more in line with its desired long-term financial and strategic model. The 2012 Restructuring Plan consists of workforce reductions, facility consolidations or closures, and supply chain and procurement efficiencies. During the year ended December 31, 2014, the Company continued to implement restructuring activities under the 2012 Restructuring Plan and recorded $0.2 million in charges for facility consolidations or closures. Under the 2012 Restructuring Plan, total costs incurred through December 31, 2014 were $112.8 million, of which $58.0 million was recorded within cost of revenues, primarily related to certain inventory and intangible asset impairment charges, and $54.8 million was recorded within restructuring and other charges in the Consolidated Statements of Operations. The restructuring activities related to this plan are substantially complete, and the Company does not expect to record significant future charges under this plan.
	Restructuring Liability
	Restructuring liabilities are reported within other accrued liabilities and other long-term liabilities in the Consolidated Balance Sheets. The following table provides a summary of changes in the restructuring liability related to the Company's plans during the year ended December 31, 2014 (in millions):
		December 31,		Charges		Cash			Non-cash			December 31,
		2013				Payments			Settlements and			2014
									Other
	Severance	$	5.6	$	52.6	$	(47.4	)	$	(1.4	)	$	9.4
	Facilities	5.1		14.4		(20.2		)	8.1			7.4
	Contract terminations and other	7.1		2.3		(8.3		)	(0.9		)	0.2
	Total	$	17.8	$	69.3	$	(75.9	)	$	5.8		$	17
	As of December 31, 2014, the Company's restructuring liability was $17.0 million, of which $9.6 million is related to severance and other charges expected to be settled by the first quarter of 2015. The remaining $7.4 million related to facility closures is expected to be paid through March 2018.

LongTerm_Debt_and_Financing_No

Long-Term Debt and Financing (Notes)	12 Months Ended
	Dec. 31, 2014
Debt Instruments [Abstract]
Long-Term Debt and Financing	Long-Term Debt and Financing
	Long-Term Debt
	The following table summarizes the Company's long-term debt (in millions, except percentages):
		As of December 31, 2014
		Amount			Effective Interest
					Rates
	Senior notes:
	3.10% fixed-rate notes, due 2016	$	300		3.25	%
	4.60% fixed-rate notes, due 2021	300			4.69	%
	4.50% fixed-rate notes, due 2024	350			4.63	%
	5.95% fixed-rate notes, due 2041	400			6.03	%
	Total senior notes	1,350.00
	Unaccreted discount	(1.0		)
	Total	$	1,349.00
	In March 2011, the Company issued $300.0 million aggregate principal amount of 3.10% senior notes due 2016 ("2016 Notes"), $300.0 million aggregate principal amount of 4.60% senior notes due 2021 ("2021 Notes"), and $400.0 million aggregate principal amount of 5.95% senior notes due 2041 ("2041 Notes"). In February 2014, the Company issued $350.0 million aggregate principal amount of 4.50% senior notes due 2024 ("2024 Notes" and, collectively the "Notes").
	The 2024 Notes are senior unsecured obligations and rank equally with all of the Company's other existing and future senior unsecured indebtedness. Interest on the Notes is payable in cash semiannually. The Company may redeem the Notes, at any time in whole or from time to time in part, subject to a make-whole premium, and, in the event of a change in control, the holders of the Notes may require the Company to repurchase for cash all or part of the Notes at a purchase price equal to 101% of the aggregate principle amount, plus accrued and unpaid interest, if any. The indenture that governs the Notes also contains various covenants, including limitations on the Company's ability to incur liens or enter into sale-leaseback transactions over certain dollar thresholds.
	The effective interest rates for the Notes include the interest on the Notes, accretion of the discount, and amortization of issuance costs. As of December 31, 2014, the Company was in compliance with all of its covenants in the indentures governing the Company's notes.
	Revolving Credit Facility
	On June 27, 2014, the Company entered into a Credit Agreement ("Credit Agreement") with certain institutional lenders and Citibank, N.A., as administrative agent, that provides for a $500.0 million unsecured revolving credit facility, with an option of the Company to increase the amount of the credit facility by up to an additional $200.0 million, subject to certain conditions. Proceeds of loans made under the Credit Agreement may be used by the Company for working capital and general corporate purposes. Revolving loans may be borrowed, repaid and reborrowed until June 27, 2019, at which time all amounts borrowed must be repaid. Borrowing may be denominated, at the Company's option in U.S. dollars, Pounds Sterling or Euro.
	Borrowings under the Credit Agreement will bear interest, at either i) a floating rate per annum equal to the base rate plus a margin of between 0.00% and 0.50%, depending on the Company's public debt rating or ii) a per annum rate equal to the reserve adjusted Eurocurrency rate, plus a margin of between 0.90% and 1.50%, depending on the Company's public debt rating. Base rate is defined as the greatest of (A) Citibank's base rate, (B) the Federal Funds rate plus 0.50% or (C) the ICE Benchmark Administration Settlement Rate applicable to dollars for a period of one month plus 1.00%. The Eurocurrency rate is determined for U.S. dollars and Pounds Sterling as the rate at which deposits in such currency are offered in the London interbank market for the applicable interest period and for Euro as the rate specified for deposits in Euro with a maturity comparable to the applicable interest period.
	As of December 31, 2014, the Company was in compliance with all covenants in the Credit Agreement, and no amounts were outstanding.
	Customer Financing Arrangements
	The Company provides certain distribution partners access to extended financing arrangements for certain end-user customers that require longer payment terms than those typically provided by the Company through 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 provider are due to the Company within 30 to 90 days from the sale of the receivable. In these transactions with the financing provider, the Company surrenders control over the transferred assets. The factored accounts receivable are isolated from the Company and put beyond the reach of the Company's creditors, even in the event of bankruptcy. The Company does not maintain effective control over the transferred assets through obligations or rights to redeem, transfer, or repurchase the receivables after they have been transferred. In 2014, the Company transitioned certain distribution partners from the third party financing program to the Company's commercial payment terms. As a result the Company's customer financing activities significantly declined from fiscal year 2013 to 2014.
	Pursuant to the financing arrangements for the sale of receivables, the Company sold net receivables of $440.3 million, $898.4 million and $677.8 million during the years ended December 31, 2014, 2013, and 2012, respectively.
	The Company received cash proceeds from the financing provider of $602.1 million, $843.9 million, and $679.8 million during the years ended December 31, 2014, 2013, and 2012, respectively. As of December 31, 2014 and December 31, 2013, the amounts owed by the financing provider were $28.0 million and $189.8 million, respectively, and were recorded in accounts receivable on the Company’s Consolidated Balance Sheets.
	The Company has provided guarantees to third-party financing companies for certain third-party financing arrangements extended to certain end-user customers, which have terms of up to four years. The Company is liable for the aggregate unpaid payments to the third-party financing company in the event of customer default. As of December 31, 2014, the Company has not been required to make any payments under these arrangements. Pursuant to these arrangements, the Company has guarantees for third-party financing arrangements of $22.2 million as of December 31, 2014.
	The portion of the receivable financed that has not been recognized as revenue is accounted for as a financing arrangement and is included in other accrued liabilities and other long-term liabilities in the Consolidated Balance Sheets. As of December 31, 2014 and 2013, the estimated cash received from the financing provider not recognized as revenue from distributors was $67.5 million and $62.3 million, respectively.

Equity_Notes

Equity (Notes)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Equity	Equity
	Cash Dividends on Shares of Common Stock
	During 2014, the Company declared two quarterly cash dividends of $0.10 per share on July 22, 2014 and on October 23, 2014, paid on September 23, 2014 and on December 23, 2014 to stockholders of record as of the close of business on September 2, 2014 and December 2, 2014, respectively, in the aggregate amount of $86.0 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 authorized committee thereof. See Note 18, Subsequent Events, for discussion of the Company's dividend declaration subsequent to December 31, 2014.
	Stock Repurchase Activities
	In February 2014, the Company's Board approved a stock repurchase program that authorized the Company to repurchase up to $2.1 billion of its common stock, including $1.2 billion pursuant to an accelerated share repurchase program ("2014 Stock Repurchase Program"). In October 2014, the Board authorized a $1.3 billion increase to the 2014 Stock Repurchase Program for a total of $3.4 billion. As of December 31, 2014, there was $1.2 billion of authorized funds remaining under the 2014 Stock Repurchase Program. In addition to repurchases under the Company’s stock repurchase program, the Company also repurchases common stock from certain employees in connection with the net issuance of shares to satisfy minimum tax withholding obligations upon the vesting of certain stock awards issued to such employees.
	The following table summarizes the Company's repurchases and retirements of its common stock under its stock repurchase programs and accelerated share repurchase, and repurchases associated with minimum tax withholdings (in millions, except per share amounts):
		Shares			Average price				Amount
		Repurchased			per share				Repurchased
	2014
	Repurchases under stock repurchase program	46.8			$	22.42			$	1,050.00
	Accelerated share repurchase(1)	49.3			$	24.35			$	1,200.00
	Repurchases for tax withholding	0.6			$	19.69			$	12.5
	2013
	Repurchases under stock repurchase program	28.9			$	19.76			$	570.6
	Repurchases for tax withholding	0.4			$	20.23			$	7.2
	2012
	Repurchases under stock repurchase program	35.8			$	18.05			$	645.6
	Repurchases for tax withholding	0.2			$	23.4			$	5
	_______________________________
	(1)	As part of the 2014 Stock Repurchase Program, the Company entered into two separate accelerated share repurchase agreements (collectively, the "ASR") with two financial institutions to repurchase $1.2 billion of the Company's common stock. The Company made an up-front payment of $1.2 billion pursuant to the ASR to repurchase the Company's common stock. The aggregate number of shares ultimately purchased was determined based on a volume weighted average repurchase price, less an agreed upon discount. The shares received with respect to the ASR have been retired. Retired shares return to authorized but unissued shares of common stock.
	The Company intends to repurchase $1.0 billion of its common stock by the end of the second quarter of 2015, as part of its three year capital return program. Future share repurchases under the Company’s stock repurchase programs 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 stock repurchase programs may be discontinued at any time. See Note 18, Subsequent Events, for discussion of the Company's stock repurchase activity subsequent to December 31, 2014.
	Accumulated Other Comprehensive (Loss) Income, Net of Tax
	The components of accumulated other comprehensive income, net of related taxes, for the years ended December 31, 2014 and December 31, 2013 were as follows (in millions):
		Unrealized				Unrealized				Foreign			Total
		Gains (Losses)				Gains (Losses)				Currency
		on Available-for-				on Cash Flow				Translation
		Sale Securities(1)				Hedges(2)				Adjustments
	Balance as of December 31, 2012	$	2.1			$	3			$	(0.4	)	$	4.7
	Other comprehensive gain (loss) before reclassifications	65.1				0.7				(3.4		)	62.4
	Amount reclassified from accumulated other	(1.0		)		(1.5		)		—			(2.5		)
	comprehensive income
	Other comprehensive gain (loss)	64.1				(0.8		)		(3.4		)	59.9
	Balance as of December 31, 2013	$	66.2			$	2.2			$	(3.8	)	$	64.6
	Other comprehensive gain (loss) before reclassifications	48.7				(4.1		)		(14.2		)	30.4
	Amount reclassified from accumulated other	(106.5		)		(2.3		)		—			(108.8		)
	comprehensive income
	Other comprehensive loss, net	(57.8		)		(6.4		)		(14.2		)	(78.4		)
	Balance as of December 31, 2014	$	8.4			$	(4.2	)		$	(18.0	)	$	(13.8	)
	________________________________
	(1)	The reclassifications out of accumulated other comprehensive income during the years ended December 31, 2014 and December 31, 2013 for realized gains on available-for-sale securities of $104.3 million and $1.0 million, respectively, are included in other income (expense), net, in the Consolidated Statements of Operations.
	(2)	The reclassifications out of accumulated other comprehensive income during the year ended December 31, 2014 for realized gains on cash flow hedges are included within research and development of $1.4 million, sales and marketing of $0.3 million, and general and administrative of $0.7 million and for realized losses within cost of revenues of $0.1 million for which the hedged transactions relate in the Consolidated Statements of Operations. The reclassifications out of accumulated other comprehensive income during the year ended December 31, 2013 for realized gains on cash flow hedges are included within cost of revenues of $1.1 million and sales and marketing of $4.3 million and for realized losses within research and development of $3.4 million and general and administrative of $0.5 million for which the hedged transactions relate in the Consolidated Statements of Operations.

Employee_Benefit_Plans_Notes

Employee Benefit Plans (Notes)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Employee Benefit Plans	Employee Benefit Plans
	Equity Incentive Plans
	The Company’s equity incentive plans include the 2006 Equity Incentive Plan (the “2006 Plan”), the 2000 Nonstatutory Stock Option Plan (the “2000 Plan”), the Amended and Restated 1996 Stock Plan (the “1996 Plan”), various equity incentive plans assumed through acquisitions, and the 2008 Employee Stock Purchase Plan (the "ESPP"). Under these plans, the Company has granted (or, in the case of acquired plans, assumed) stock options, restricted stock units ("RSUs"), restricted stock awards ("RSAs"), and performance share awards ("PSAs").
	As of December 31, 2014, a total of approximately 82.3 million shares of common stock were reserved for future issuance upon exercise of stock options and vesting of RSUs, RSAs, and PSAs, and for the future grant of share-based compensation awards under the Company's equity incentive plans.
	The 2006 Plan was adopted and approved by the Company’s stockholders in May 2006. To date, the Company's stockholders have approved a share reserve of 149.5 million shares of common stock plus the addition of any shares subject to options under the 2000 Plan and the 1996 Plan that were outstanding as of May 18, 2006, and that subsequently expire unexercised, up to a maximum of an additional 75.0 million shares. As of December 31, 2014, the 2006 Plan had 27.1 million shares subject to currently outstanding equity awards and 47.8 million shares available for future issuance. Options granted under the 2006 Plan have a maximum term of seven years from the date of grant, and generally vest and become exercisable over a four-year period. Subject to the terms of change of control severance agreements, and except for a limited number of shares allowed under the 2006 Plan, RSUs or PSAs that vest solely based on continuing employment or provision of services will vest in full no earlier than three years from the grant date, or in the event vesting is based on factors other than continued future provision of services, such awards will vest in full no earlier than one year from the grant date.
	During 2012 through 2014, the Company completed the acquisitions of Mykonos, Contrail, and WANDL and assumed their respective plans: Mykonos Software, Inc. 2010 Stock Plan; Contrail Systems Inc. 2012 Stock Plan, and WANDL, Inc. 2013 Restricted Stock Unit Plan. In connection with these plans, the Company assumed stock options, RSUs, RSAs, and PSAs and exchanged the assumed awards for Juniper Networks' stock options, RSUs, RSAs, and PSAs, respectively. No additional awards can be granted under these plans. The Company assumed an aggregate of 8.5 million shares of stock options, RSUs, RSAs, and PSAs in connection with the acquisitions of Mykonos, Contrail, and WANDL. As of December 31, 2014 stock options, RSUs, RSAs, and PSAs representing approximately 4.1 million shares of common stock were outstanding under all awards assumed through the Company's acquisitions.
	The ESPP was adopted in May 2008. To date, the Company's stockholders have approved a share reserve of 19.0 million shares of the Company's common stock for issuance under the ESPP. The ESPP permits eligible employees to acquire shares of the Company’s common stock at a 15% discount to the offering price (as determined in the ESPP) through periodic payroll deductions of up to 10% of base compensation, subject to individual purchase limits of 6,000 shares in any twelve-month period or $25,000 worth of stock, determined at the fair market value of the shares at the time the stock purchase option is granted, in one calendar year. As of December 31, 2014, approximately 15.7 million shares have been issued and 3.3 million shares remain available for future issuance under the ESPP.
	Stock Option Activities
	Since 2006, the Company has granted stock option awards that have a maximum contractual life of seven years from the date of grant. Prior to 2006, stock option awards generally had a ten-year contractual life from the date of grant.
	The following table summarizes the Company’s stock option activity and related information as of and for the three years ended December 31, 2014 (in millions, except for per share amounts and years):
		Outstanding Options
		Number of Shares			Weighted Average				Weighted Average		Aggregate
					Exercise Price				Remaining		Intrinsic
					per Share				Contractual Term		Value
									(In Years)
	Balance as of December 31, 2011	38.6			$	23.98			3.7		$	75.3
	Granted	3.1			22.81
	Assumed(*)	0.9			0.57
	Canceled	(2.8	)		26.64
	Exercised	(3.6	)		11.71
	Expired	(2.1	)		26.97
	Balance as of December 31, 2012	34.1			$	24.13			3.1		$	52.5
	Canceled	(1.3	)		29.56
	Exercised	(5.6	)		15.58
	Expired	(4.1	)		28.35
	Balance as of December 31, 2013	23.1			$	25.15			2.4		$	44.6
	Canceled	(0.6	)		30.15
	Exercised	(5.4	)		19.76
	Expired	(7.2	)		29.11
	Balance as of December 31, 2014	9.9			$	24.87			2		$	24.7
	As of December 31, 2014:
	Vested and expected-to-vest options	9.8			$	25			2		$	23.6
	Exercisable options	9.1			$	25.88			1.7		$	15.9
	_____________________________
	(*)	Stock options assumed in connection with the acquisition of Contrail.
	Aggregate intrinsic value represents the difference between the Company’s closing stock price on the last trading day of the period, which was $22.32 per share as of December 31, 2014 and the exercise price, multiplied by the number of related options. The pre-tax intrinsic value of options exercised, representing the difference between the fair market value of the Company’s common stock on the date of the exercise and the exercise price of each option, was $33.4 million, $29.4 million, and $27.9 million for 2014, 2013, and 2012, respectively. Total fair value of options vested during 2014, 2013, and 2012 was $20.8 million, $45.2 million, and $70.9 million, respectively.
	The following table summarizes additional information regarding outstanding and exercisable options as of December 31, 2014:
			Options Outstanding									Options Exercisable
	Range of Exercise Price		Number Outstanding			Weighted Average		Weighted Average				Number	Weighted Average
	(In dollars)		(In millions)			Remaining		Exercise Price				Exercisable	Exercise Price
						Contractual Life		(In dollars)				(In millions)	(In dollars)
						(In years)
	$0.03 - $15.09		1.7			3.6		$	9.58			1.3	$	12.23
	$16.39 - $22.59		1.4			1.5		20.36				1.2	20.34
	$22.74 - $24.61		1.1			2		23.85				0.9	23.81
	$24.73 - 24.73		0.1			0.4		24.73				0.1	24.73
	$25.16- $25.16		1.2			0.2		25.16				1.2	25.16
	$25.19 - $26.90		1			1.3		26.24				1	26.24
	$26.97 - $29.89		1.6			1.8		28.71				1.6	28.7
	$30.01 - $38.93		0.7			2.9		33.57				0.7	33.6
	$40.26 - $40.26		0.7			2.8		40.26				0.7	40.26
	$44.00 - $44.00		0.4			3		44				0.4	44
	$0.03 - $44.00		9.9			2		$	24.87			9.1	$	25.88
	Restricted Stock Unit, Restricted Stock Award, and Performance Share Award Activities
	RSUs and RSAs generally vest over a period of three to four years from the date of grant and PSAs generally vest over a period of two to three years provided that certain annual performance targets and other vesting criteria are met. Until vested, RSUs and PSAs do not have the voting and dividend participation rights of common stock and the shares underlying the awards are not considered issued and outstanding.
	The following table summarizes the Company’s RSU, RSA, and PSA activity and related information as of and for the three years ended December 31, 2014 (in millions, except per share amounts and years):
		Outstanding RSUs, RSAs, and PSAs
		Number of Shares			Weighted Average				Weighted Average		Aggregate
					Grant-Date Fair				Remaining		Intrinsic
					Value per Share				Contractual Term		Value
									(In Years)
	Balance as of December 31, 2011	19.6			$	30.27			1.5		$	400.5
	RSUs granted	9.9			20.79
	RSUs assumed(1)(2)	0.2			22.21
PSAs granted(3)	2.2			23.07
RSAs assumed(2)	5.8			19.59
RSUs vested(8)	(3.1	)		27.04
PSAs vested(8)	(1.9	)		18.21
RSAs vested(8)	(0.7	)		19.59
RSUs canceled	(2.9	)		27.77
PSAs canceled	(2.3	)		29.71
Balance as of December 31, 2012	26.8			$	27.76			1.7		$	565
RSUs granted	10.3			20.32
PSAs granted(4)	2.2			21.27
RSUs vested(8)	(6.1	)		26.15
PSAs vested(8)	(1.1	)		28.52
RSAs vested(8)	(1.6	)		19.59
RSUs canceled	(3.4	)		22.99
PSAs canceled	(1.7	)		29.1
Balance as of December 31, 2013	25.4			$	23.44			1.1		$	573.5
RSUs granted(5)(9)	10			22.52
RSUs assumed(6)	0.4			22.66
RSAs assumed(6)	0.9			22.66
PSAs granted(7)(9)	1.4			24.25
PSAs assumed(6)	0.2			22.66
RSUs vested(8)	(7.3	)		22.98
RSAs vested(8)	(1.4	)		19.59
PSAs vested(8)	(1.1	)		36.19
RSUs canceled	(4.0	)		21.63
PSAs canceled	(3.2	)		30.43
Balance at December 31, 2014	21.3			$	22.05			1.1		$	475
As of December 31, 2014
Vested and expected-to-vest RSUs, RSAs,	17.7			$	21.99			1		$	395.2
and PSAs
________________________________
(1)	RSUs assumed in connection with the acquisition of Mykonos
-2	RSUs and RSAs assumed in connection with the acquisition of Contrail.
-3	The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee are achieved at target is 0.9 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 2.2 million shares.
-4	The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee are achieved at target is 1.1 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 2.2 million shares.
(5)	Includes service-based and market-based RSUs granted under the 2006 Plan according to its terms.
-6	RSUs, RSAs, and PSAs assumed in connection with the acquisition of WANDL.
-7	The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee are achieved at target is 0.9 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 1.4 million shares.
-8	Total fair value of RSUs, RSAs, and PSAs vested during 2014, 2013, and 2012 was $210.1 million, $221.5 million, and $132.0 million, respectively.
-9	On February 20, 2014, the Company announced its intention to initiate a quarterly cash dividend of $0.10 per share of common stock in the third quarter of 2014. As a result of the Company's announcement, the grant date fair value of RSUs and PSAs granted after the announcement date were reduced by the present value of the dividends expected to be paid on the underlying shares of common stock during the requisite and derived service period as these awards are not entitled to receive dividends until vested. The Company paid quarterly cash dividends in the third and fourth quarter of 2014 of $0.10 per share totaling $86.0 million. The declaration and amount of any future cash dividends are at the discretion of the Board of Directors and will depend on the Company's financial performance, economic outlook, and any other relevant considerations.
Shares Available for Grant
The following table presents the stock activity and the total number of shares available for grant under the 2006 Plan as of December 31, 2014 (in millions):
	Number of Shares
Balance as of December 31, 2013	49.1
RSUs and PSAs granted (1)	(24.1	)
RSUs and PSAs canceled (1)	15
Options canceled (2)	0.6
Options expired (2)	7.2
Balance as of December 31, 2014	47.8
________________________________
(1)	RSUs and PSAs with a per share or unit purchase price lower than 100% of the fair market value of the Company's common stock on the day of the grant under the 2006 Plan are counted against shares authorized under the plan as two and one-tenth shares of common stock for each share subject to such award. The number of shares subject to PSAs granted represents the maximum number of shares that may be issued pursuant to the award over its full term.
(2)	Includes canceled or expired options under the 1996 Plan and the 2000 Plan that expired after May 18, 2006, which become available for grant under the 2006 Plan according to its terms.
Employee Stock Purchase Plan
The Company's ESPP is implemented in a series of offering periods, each six months in duration, or a shorter period as determined by the Board. Employees purchased approximately 2.9 million, 3.3 million, and 3.5 million shares of common stock through the ESPP at an average exercise price of $19.30, $16.53, and $16.26 per share during 2014, 2013, and 2012, respectively.
Valuation Assumptions
The weighted-average assumptions used and the resulting estimates of fair value for stock options, ESPP, and market-based RSUs were as follows:
	Years Ended December 31,
	2014		2013		2012
Stock Options(1):
Volatility	—		—		45%
Risk-free interest rate	—		—		0.70%
Expected life (years)	—		—		4.2
Dividend yield	—		—		—
Weighted-average fair value per share	—		—		$8.47
ESPP(1):
Volatility	30%		36%		47%
Risk-free interest rate	0.10%		0.10%		0.10%
Expected life (years)	0.5		0.5		0.5
Dividend yield	0% - 1.8%		—		—
Weighted-average fair value per share	$5.72		$5.54		$5.53
Market-based RSUs(2)
Volatility	36%		—		—
Risk-free interest rate	1.60%		—		—
Dividend yield	0% - 2.0%		—		—
Weighted-average fair value per share	$16.89		—		—
________________________________
(1)	The Black-Scholes-Merton option-pricing model is utilized to estimate the fair value of stock options and ESPP.
(2)	The fair value of market-based RSUs utilizes the Monte Carlo simulation option pricing model. The Company amortizes the fair value of these awards over the derived service period adjusted for estimated forfeitures for each separately vesting tranche of the award. Provided that the derived service is rendered, the total fair value of the market-based RSUs at the date of grant is recognized as compensation expense even if the market condition is not achieved. However, the number of shares that ultimately vest can vary significantly with the performance of the specified market criteria.
Share-Based Compensation Expense
Share-based compensation expense associated with stock options, RSUs, RSAs, PSAs, and ESPP was recorded in the following cost and expense categories in the Company's Consolidated Statements of Operations (in millions):
	Years Ended December 31,
	2014				2013				2012
Cost of revenues - Product	$	5			$	4.7			$	4.6
Cost of revenues - Service	14.2				15.4				17
Research and development	134.5				127.6				109.1
Sales and marketing	60.2				70.9				81.6
General and administrative	26.1				26				31.1
Total	$	240			$	244.6			$	243.4
The following table summarizes share-based compensation expense by award type (in millions):
	Years Ended December 31,
	2014				2013				2012
Stock options	$	14.9			$	31.5			$	58.9
RSUs, RSAs, and PSAs	209.7				196.8				163.7
ESPP	15.4				16.3				20.8
Total	$	240			$	244.6			$	243.4
The following table presents unrecognized compensation cost, adjusted for estimated forfeitures, recognized over a weighted-average period related to unvested stock options, RSUs, RSAs, and PSAs as of December 31, 2014 (in millions, except years):
	Unrecognized				Weighted Average
	Compensation Cost				Period
					(In Years)
Stock options	$	11.4			1.3
RSUs, RSAs, and PSAs	$	257.8			1.7
401(k) Plan
The Company maintains a savings and retirement plan qualified under Section 401(k) of the Internal Revenue Code of 1986, as amended (the "IRC"). Employees meeting the eligibility requirements, as defined under the IRC, may contribute up to the statutory limits each year. The Company currently matches 30% of all eligible employee contributions which vest immediately. The Company’s matching contributions to the plan totaled $20.2 million, $20.7 million, and $20.2 million during the years ended December 31, 2014, 2013, and 2012, respectively.
Deferred Compensation Plan
The Company’s non-qualified deferred compensation (“NQDC”) plan is an unfunded and unsecured deferred compensation arrangement. Under the NQDC plan, officers and other senior employees may elect to defer a portion of their compensation and contribute such amounts to one or more investment funds. The NQDC plan assets are included within short-term investments and offsetting obligations are included within accrued compensation in the Consolidated Balance Sheets. The investments are considered trading securities and are reported at fair value. The realized and unrealized holding gains and losses related to these investments are recorded in other income (expense), net, and the offsetting compensation expense is recorded as operating expenses in the Consolidated Statements of Operations. The deferred compensation liability under the NQDC plan was approximately $16.3 million and $15.4 million as of December 31, 2014 and December 31, 2013, respectively.

Segments_Notes

Segments (Notes)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segments	Segments
	In 2014, the Company realigned its organization into a One-Juniper structure which includes consolidating each of the Company's R&D and go-to-market functions to reduce complexity, increase clarity of responsibilities, and improve efficiency. As a result of these changes, the consolidated business is considered to be one reportable segment, consistent with how the Company’s chief operating decision maker ("CODM") views the business, allocates resources, and assesses the performance of the Company.
	The Company continues to sell its high-performance network products and service offerings across routing, switching, and security to service provider and enterprise markets.
	The following table presents net revenues by product and service (in millions):
		Years Ended December 31,
		2014		2013		2012
	Routing	$	2,223.90	$	2,318.00	$	2,037.60
	Switching	721.2		638		554.8
	Security	463.6		563.9		669.7
	Total product	3,408.70		3,519.90		3,262.10
	Total service	1,218.40		1,149.20		1,103.30
	Total	$	4,627.10	$	4,669.10	$	4,365.40
	The Company attributes revenues to geographic region based on the customer’s ship-to location. The following table presents net revenues by geographic region (in millions):
		Years Ended December 31,
		2014		2013		2012
	Americas:
	United States	$	2,410.60	$	2,381.50	$	2,067.50
	Other	219.7		232		218.4
	Total Americas	2,630.30		2,613.50		2,285.90
	Europe, Middle East, and Africa	1,263.30		1,256.90		1,266.30
	Asia Pacific	733.5		798.7		813.2
	Total	$	4,627.10	$	4,669.10	$	4,365.40
	During the years ended December 31, 2014 and 2013, no customer accounted for greater than 10% of the Company's net revenues. During the year ended December 31, 2012, Verizon accounted for 10.3% of the Company's net revenues.
	The following table presents geographic information for property and equipment, net and purchased intangible assets, net (in millions):
		As of December 31,
		2014		2013
	United States	$	871.7	$	885.6
	International	95		103.6
	Property and equipment, net and purchased intangible assets, net	$	966.7	$	989.2
	The Company tracks assets by physical location. The majority of the Company’s assets, excluding cash and cash equivalents and investments, as of December 31, 2014 and December 31, 2013, were attributable to U.S. operations.

Income_Taxes_Notes

Income Taxes (Notes)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	The components of pretax (loss) income and noncontrolling interest are summarized as follows (in millions):
		Years Ended December 31,
		2014			2013			2012
	Domestic	$	(509.7	)	$	248.7		$	114.1
	Foreign	423.4			276.8			177.4
	Total pretax (loss) income	$	(86.3	)	$	525.5		$	291.5
	The provision for income taxes is summarized as follows (in millions):
		Years Ended December 31,
		2014			2013			2012
	Current provision (benefit):
	Federal	$	180.1		$	(12.9	)	$	94.3
	States	15.2			(5.0		)	8.4
	Foreign	33.7			32.5			37.1
	Total current provision (benefit)	229			14.6			139.8
	Deferred provision (benefit):
	Federal	17.3			51.2			(28.8		)
	States	1.2			(2.7		)	(1.5		)
	Foreign	0.5			22.6			3.5
	Total deferred provision (benefit)	19			71.1			(26.8		)
	Income tax benefits attributable to employee stock plan activity	—			—			(8.0		)
	Total provision (benefit) for income taxes	$	248		$	85.7		$	105
	The provision for income taxes differs from the amount computed by applying the federal statutory rate to pretax (loss) income as follows (in millions):
		Years Ended December 31,
		2014			2013			2012
	Expected (benefit) provision at 35% rate	$	(30.2	)	$	184		$	102
	State taxes (benefit), net of federal benefit	9.5			(3.6		)	2
	Foreign income at different tax rates	(90.2		)	(37.7		)	(11.6		)
	Research and development credits	(17.1		)	(32.5		)	(0.5		)
	Share-based compensation	25.3			25.6			22.4
	Non-deductible goodwill impairment	297.5			—			—
	Gain on sale of Junos Pulse	75.6			—			—
	Release of valuation allowance	(22.8		)	—			(3.4		)
	Settlement with tax authorities	—			(28.3		)	—
	Domestic production activities	(6.8		)	(26.3		)	—
	Non-deductible compensation	3.2			1.5			0.6
	Equity investment gain on acquisition	—			—			(5.3		)
	Other	4			3			(1.2		)
	Total provision for income taxes	$	248		$	85.7		$	105
	In 2014, the Company has provided tax on a pre-tax loss primarily due to the non-deductible goodwill charge. In 2013, the Company recorded $64.2 million of net income tax benefit related to items unique to the year. These amounts included $19.7 million for a multi-year claim related to the U.S. production activities deduction, $28.3 million for a tax settlement with the IRS, and $16.2 million of U.S. federal R&D tax credit resulting from the American Taxpayer Relief Act of 2012 signed on January 2, 2013, which retroactively reinstated the U.S. federal R&D tax credit from January 1, 2012 to December 31, 2013.
	Deferred income taxes reflect the net tax effects of tax carry-forward items and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company's deferred tax assets and liabilities are as follows (in millions):
		As of December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss carry-forwards	$	1.3		$	1.1
	Foreign tax credit carry-forwards	69.7			63.4
	Research and other credit carry-forwards	122.5			106.6
	Deferred revenue	104.9			71
	Stock-based compensation	55.8			86.1
	Reserves and accruals not currently deductible	129.8			153.9
	Other	19.8			13.7
	Total deferred tax assets	503.8			495.8
	Valuation allowance	(144.5		)	(155.7		)
	Deferred tax assets, net of valuation allowance	359.3			340.1
	Deferred tax liabilities:
	Property and equipment basis differences	(35.6		)	(3.1		)
	Purchased intangibles	(16.7		)	(10.1		)
	Unremitted foreign earnings	(260.6		)	(258.9		)
	Deferred compensation and other	(5.1		)	(38.7		)
	Other	—			(0.4		)
	Total deferred tax liabilities	(318.0		)	(311.2		)
	Net deferred tax assets	$	41.3		$	28.9
	The breakdown between current and long-term deferred tax assets and deferred tax liabilities are as follows (in millions):
		As of December 31,
	2014			2013
Current deferred tax assets	$	147		$	79.8
Long-term deferred tax assets	1.7			2.4
Long-term deferred tax liabilities	(107.4		)	(53.3		)
Total net deferred tax assets	$	41.3		$	28.9
As of December 31, 2014, and 2013, the Company had a valuation allowance on its U.S. domestic deferred tax assets of approximately $144.5 million and $155.7 million, respectively. The balance at December 31, 2014 consisted of approximately $125.2 million and $9.7 million against the Company's California and Massachusetts deferred tax assets, respectively, which the Company believes are not more likely than not to be utilized in future years. The remaining deferred tax assets on which the Company recorded a valuation allowance are approximately $9.6 million related to losses that are capital in nature and may carry forward to offset future capital gains only. The valuation allowance decreased $11.2 million in 2014 related to utilization of losses that are capital in nature offset by the increase in the California R&D credit. Valuation allowance increased in 2013 by $14.7 million related to an increase in the California R&D credit.
As of December 31, 2014, the Company had federal and California net operating loss carry-forwards of approximately $1.6 million and $27.8 million, respectively. The Company also had California tax credit carry-forwards of approximately $231.9 million. Approximately $16.2 million of the benefit from the California tax credit carry-forwards will be credited to additional paid-in capital when realized on the Company's income tax returns. Unused net operating loss carry-forwards will expire at various dates beginning in the year 2021. The California tax credit carry-forwards will carry forward indefinitely.
The Company provides U.S. income taxes on the earnings of foreign subsidiaries unless the subsidiaries' earnings are considered indefinitely reinvested outside of the United States. The Company has made no provision for U.S. income taxes on approximately $1.9 billion of cumulative undistributed earnings of certain foreign subsidiaries through December 31, 2014. These earnings are considered indefinitely invested in operations outside of the U.S., as the Company intends to utilize these amounts to fund future expansion of its international operations. If these earnings were distributed to the United States in the form of dividends or otherwise, or if the shares of the relevant foreign subsidiaries were sold or otherwise transferred, the Company would be subject to additional U.S. income taxes (subject to an adjustment for foreign tax credits) and foreign withholding taxes. Determination of the amount of unrecognized deferred income tax liability related to these earnings is not practicable.
As of December 31, 2014, 2013, and 2012 the total amount of gross unrecognized tax benefits was $199.2 million, $137.6 million, and $136.1 million, respectively. As of December 31, 2014, approximately $164.9 million of the $199.2 million gross unrecognized tax benefits, if recognized, would affect the effective tax rate.
A reconciliation of the beginning and ending amount of the Company's total gross unrecognized tax benefits was as follows (in millions):
	Years Ended December 31,
	2014			2013			2012
Balance at beginning of year	$	137.6		$	136.1		$	132.2
Tax positions related to current year:
Additions	62.5			15.8			8.8
Tax positions related to prior years:
Additions	0.6			22.6			0.9
Reductions	—			(2.2		)	—
Settlements	—			(31.1		)	(1.2		)
Lapses in statutes of limitations	(1.5		)	(3.6		)	(4.6		)
Balance at end of year	$	199.2		$	137.6		$	136.1
As of December 31, 2014, 2013, and 2012 the Company had accrued interest and penalties related to unrecognized tax benefits of $22.3 million, $18.4 million, and $16.7 million, respectively, within other long-term liabilities in the Consolidated Balance Sheets. The Company recognized an expense for net interest and penalties of $2.8 million and $0.6 million, and a benefit of $0.6 million in its Consolidated Statements of Operations during the years ended December 31, 2014, 2013, and 2012, respectively.
The Company engages in continuous discussions and negotiations with tax authorities regarding tax matters in various jurisdictions. There is a greater than remote likelihood that the balance of the gross unrecognized tax benefits will decrease by approximately $3.2 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.
In 2013, the Company executed a closing agreement with the Appeals Division of the IRS related to its intercompany R&D cost sharing arrangement for the license of intangibles acquired in 2004, 2005, and 2006. The Company reached a final resolution with the IRS on all proposed adjustments for all tax years through 2006, which resulted in a settlement of approximately $19.6 million, including interest.
The Company conducts business globally and, as a result, Juniper Networks or one or more of its subsidiaries files income tax returns in the U.S. federal jurisdiction and various state and foreign jurisdictions. In the normal course of business the Company is subject to examination by taxing authorities throughout the world, including such major jurisdictions as the Netherlands, U.K., France, Germany, Japan, China, Australia, India, and the U.S. With few exceptions, the Company is no longer subject to U.S. federal, state and local, and non-U.S. income tax examinations for years before 2004.
The Company is currently under examination by the IRS for the 2007 through 2009 tax years and the California Franchise Tax Board for the 2004 through 2006 tax years. The Company is also subject to separate ongoing examinations by the India tax authorities for the 2004 tax year, 2004 through 2008 tax years, and the 2008 through 2010 tax years. The Company is not aware of any other examinations by tax authorities in any other major jurisdictions in which it files income tax returns as of December 31, 2014.
In 2008, the Company received a proposed adjustment from the India tax authorities related to the 2004 tax year. In 2009, the India tax authorities commenced a separate investigation of our 2004 through 2008 tax returns and are disputing the Company's determination of taxable income due to the cost basis of certain fixed assets. The Company accrued $4.6 million in penalties and interest in 2009 related to this matter. The Company understands that in accordance with the administrative and judicial process in India, the Company may be required to make payments that are substantially higher than the amount accrued in order to ultimately settle this issue. The Company strongly believes that any assessment it may receive in excess of the amount accrued would be inconsistent with applicable India tax laws and intends to defend this position vigorously.
The Company is pursuing all available administrative remedies relative to these matters. The Company believes that it has adequately provided for any reasonably foreseeable outcomes related to these proposed adjustments and the ultimate resolution of these matters is unlikely to have a material effect on its consolidated financial condition or results of operations; however there is still a possibility that an adverse outcome of these matters could have a material effect on its consolidated financial condition and results of operations.

Net_Income_per_Share_Notes

Net Income per Share (Notes)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Net Income Per Share	Net Income per Share
	The Company computed basic and diluted net (loss) income per share attributable to Juniper Networks common stockholders as follows (in millions, except per share amounts):
		Years Ended December 31,
		2014			2013		2012
	Numerator:
	Net (loss) income	$	(334.3	)	$	439.8	$	186.5
	Denominator:
	Weighted-average shares used to compute basic net income per share	457.4			501.8		520.9
	Dilutive effect of employee stock awards	—			8.5		5.3
	Weighted-average shares used to compute diluted net income	457.4			510.3		526.2
	per share
	Net (loss) income per share attributable to Juniper Networks common
	stockholders:
	Basic	$	(0.73	)	$	0.88	$	0.36
	Diluted	$	(0.73	)	$	0.86	$	0.35
	Anti-dilutive:
	Potential anti-dilutive shares	20.8			13.2		32.3
	Basic net income per share is computed using net (loss) income available to common stockholders and the weighted-average number of common shares outstanding for the period. Diluted net income per share is computed using net (loss) income available to common stockholders and the weighted-average number of common shares outstanding plus potentially dilutive common shares outstanding during the period. Dilutive potential common shares consist of common shares issuable upon exercise of stock options, issuances of ESPP, and vesting of RSUs, RSAs, and PSAs. The Company includes the common shares underlying PSAs in the calculation of diluted net income per share when they become contingently issuable and excludes such shares when they are not contingently issuable. Potentially dilutive common shares were excluded from the computation of diluted net loss per share because their effect would be anti-dilutive.

Commitments_and_Contingencies_

Commitments and Contingencies (Notes)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	Operating Leases
	The following table summarizes the Company’s future minimum payments under non-cancelable operating leases for each of the next five years and thereafter as of December 31, 2014 (in millions):
	Years Ending December 31,	Amount
	2015	$	41.2
	2016	30.1
	2017	22
	2018	14.3
	2019	7.5
	Thereafter	22
	Total	$	137.1
	The Company leases its facilities and certain equipment under non-cancelable operating leases that expire at various dates through October 31, 2024. Certain leases require the Company to pay variable costs such as taxes, maintenance, and insurance and include renewal options and escalation clauses. Rent expense for 2014, 2013, and 2012 was approximately $46.0 million, $52.8 million, and $63.2 million, respectively.
	Purchase Commitments with Contract Manufacturers and Suppliers
	In order to reduce manufacturing lead times and ensure 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 $476.2 million as of December 31, 2014.
	The Company establishes a liability in connection with purchase commitments related to quantities in excess of its demand forecasts or obsolete materials charges for components purchased by the contract manufacturers based on the Company’s demand forecast or customer orders. As of December 31, 2014, the Company had accrued $25.3 million based on its estimate of such charges. This includes $9.4 million related to net losses on firm and non-cancelable purchase commitments.
	Long-Term Debt and Interest Payment on Long-Term Debt
	As of December 31, 2014, the Company held long-term debt consisting of senior notes with a carrying value of $1,349.0 million. Of these Notes, $300.0 million will mature in 2016 and bears interest at a fixed rate of 3.10%, $300.0 million will mature in 2021 and bears interest at a fixed rate of 4.60%, $350.0 million will mature in 2024 and bears interest at a fixed rate of 4.50%, and $400.0 million will mature in 2041 and bears interest at a fixed rate of 5.95%. Interest on the Notes is payable semiannually. See Note 10, Long-Term Debt and Financing, for further discussion of the Company's long-term debt.
	Other Contractual Obligations
	As of December 31, 2014, other contractual obligations primarily consisted of $46.0 million in indemnity-related and service related escrows, as required in connection with certain asset purchases and acquisitions completed between 2005 and 2014, campus build-out obligations of $3.5 million, and $19.2 million of agreements that are firm, non-cancelable and specify terms, including: fixed or minimum quantities to be purchased; fixed, minimum or variable price provisions; and the approximate timing of payment.
	Tax Liabilities
	As of December 31, 2014, the Company had $177.5 million included in long-term income taxes payable in the Consolidated Balance Sheets for unrecognized tax positions. At this time, the Company is unable to make a reasonably reliable estimate of the timing of payments related to this amount due to uncertainties in the timing of tax audit outcomes.
	Guarantees
	The Company enters into agreements with customers that contain indemnification provisions relating to potential situations where claims could be alleged that the Company’s products infringe the intellectual property rights of a third-party. The Company also has financial guarantees consisting of guarantees of product and service performance, guarantees related to third-party customer-financing arrangements, custom and duty guarantees, and standby letters of credit for certain lease facilities. As of December 31, 2014 and December 31, 2013, the Company had $26.2 million and $40.1 million, respectively, in financing arrangements, bank guarantees, and standby letters of credit related to these financial guarantees, of which $22.2 million in financing guarantees was recorded in other accrued liabilities and other long-term liabilities in the Consolidated Balance Sheets as of December 31, 2014. See Note 10, Long-Term Debt and Financing, for further discussion of the Company's third-party customer financing arrangements that contain guarantee provisions.
	Legal Proceedings
	Investigations
	The U.S. Securities and Exchange Commission (SEC) and the U.S. Department of Justice (DOJ) are conducting investigations into possible violations by the Company of the U.S. Foreign Corrupt Practices Act (FCPA). The Company is cooperating with these agencies regarding these matters. The Company’s Audit Committee, with the assistance of independent advisors, has been investigating and conducting a thorough review of possible violations of the FCPA, and has made recommendations for remedial measures, including employee disciplinary actions in foreign jurisdictions, which the Company has implemented and continues to implement. The Company is unable to predict the duration, scope or outcome of the SEC and DOJ investigations, but believes that an adverse outcome is reasonably possible. However, the Company is not able to estimate a reasonable range of possible loss. The SEC and/or DOJ could take action against us or we could agree to settle. In such event, we could be required to pay substantial fines and sanctions and/or implement additional remedial measures; in addition, it may be determined that we violated the FCPA.
	Other Litigation
	In addition to the investigations discussed above, the Company is involved in other disputes, litigation, and other legal actions. The Company is aggressively defending these current litigation matters, and while there can be no assurances and the outcome of these matters is currently not determinable, and the Company currently believes that none of these existing claims or proceedings are likely to have a material adverse effect on its financial position. There are many uncertainties associated with any litigation and these actions 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.
	We record an accrual for loss contingencies for legal proceedings when we believe that an unfavorable outcome is both (a) probable and (b) the amount or range of any possible loss is reasonably estimable. We have not recorded any accrual for loss contingencies associated with such legal proceedings or the investigations discussed above.

Selected_Quarterly_Financial_D

Selected Quarterly Financial Data (Unaudited) (Notes)	12 Months Ended
	Dec. 31, 2014
Selected Quarterly Financial Information [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited)
	The tables below set forth selected unaudited financial data for each quarter of the two years ended December 31, 2014 (in millions, except per share amounts):
	Year Ended December 31, 2014		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Net revenues:
	Product		$	876		$	929.2		$	809.5		$	794
	Service		294.1			300.3			316.4			307.6
	Total net revenues		1,170.10			1,229.50			1,125.90			1,101.60
	Cost of revenues:
	Product		326.6			359.3			290			310.9
	Service		123.4			122			121.1			115.6
	Total cost of revenues (1)		450			481.3			411.1			426.5
	Gross margin		720.1			748.2			714.8			675.1
	Operating expenses:
	Research and development		264			255.5			253.2			233.5
	Sales and marketing		273.4			258			249.2			243
	General and administrative		74.9			60.6			55			40.6
	Restructuring and other (credit) charges(1)		114			58.2			(15.0		)	9.8
	Impairment of goodwill(2)		—			—			—			850
	Total operating expenses		726.3			632.3			542.4			1,376.90
	Operating (loss) income		(6.2		)	115.9			172.4			(701.8		)
	Other income (expense), net(3)		154.2			178.6			(6.8		)	7.4
	Income (loss) before income taxes		148			294.5			165.6			(694.4		)
	Income tax provision		37.4			73.4			62			75.2
	Net income (loss)		$	110.6		$	221.1		$	103.6		$	(769.6	)
	Net income (loss) per share:(4)
	Basic		$	0.23		$	0.47		$	0.23		$	(1.81	)
	Diluted		$	0.22		$	0.46		$	0.23		$	(1.81	)
	Cash dividends declared per common stock(5)		$	—		$	—		$	0.1		$	0.1
	_______________________________
	(1)	In the first quarter of 2014, the company initiated a 2014 Restructuring Plan, which consisted of $84.7 million asset write-downs, $28.0 million of severance costs, and $0.8 million of contract terminations that were recorded in restructuring and other charges. In addition, the Company recorded inventory write-downs related to the acceleration of the end-of-service life of certain products totaling $8.4 million to cost of revenues. In the second quarter, the Company recorded $9.9 million of severance costs, $37.6 million of facility consolidation and closures, $8.9 million of asset write-downs, and $1.5 million of contract terminations that were recorded to restructuring and other charges. The Company also recorded inventory write-downs of $11.5 million and a charge related to products with contract manufacturers of $2.3 million for acceleration of the end-of-life service of certain products to cost of revenues. In the third quarter, the Company recorded $7.1 million of severance costs, a benefit of $25.0 million of facility consolidation and closures as a result of a lease assignment, and $2.9 million of asset write-downs, that were recorded to restructuring and other (credit) charges. In the fourth quarter, the Company recorded $6.9 million in severance costs, $1.6 million of facility consolidation and closures, and $20.6 million in asset impairment and write-downs.
	(2)	During the fourth quarter of 2014, the Company recorded an $850.0 million goodwill impairment charge related to its Security reporting unit.
	(3)	In the first quarter of 2014, the Company recorded a gain of $163.0 million related to the sale of investments which were converted from privately-held investments to publicly-traded equity upon IPO. In the second quarter, the Company entered into a settlement agreement with PAN, which resulted in a realized gain on legal settlement of $195.3 million, net of legal fees. All such PAN securities were sold in the third quarter, and the Company recorded an additional $0.8 million gain. In the fourth quarter, the Company recorded a gain of $19.6 million on the sale of Junos Pulse.
	(4)	Net income (loss) per share is computed independently. Therefore, the sum of the quarterly net income per share may not equal the total computed for the year or any cumulative interim period.
	(5)	On July 22, 2014 and October 23, 2014 the company declared a quarterly cash dividend of $0.10 per share of common stock to stockholders on record as of the close of business September 2, 2014 and December 2, 2014, respectively.
	Year Ended December 31, 2013		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Net revenues:
	Product		$	781.8		$	863.8		$	900.8		$	973.5
	Service		277.4			286.9			284.8			300.1
	Total net revenues		1,059.20			1,150.70			1,185.60			1,273.60
	Cost of revenues:
	Product		278.2			321.3			325.5			351.6
	Service		110.2			108.9			113.6			118.4
	Total cost of revenues(2)		388.4			430.2			439.1			470
	Gross margin		670.8			720.5			746.5			803.6
	Operating expenses:
	Research and development(1)		262.2			257.7			264.6			258.7
	Sales and marketing(4)		256.1			267.1			269.5			283.2
	General and administrative(4)		58.5			49.2			61.4			48.2
	Restructuring and other charges(2)		7			8			6			18.1
	Total operating expenses		583.8			582			601.5			608.2
	Operating income		87			138.5			145			195.4
	Other expense, net		(10.1		)	(12.6		)	(7.5		)	(10.2		)
	Income before income taxes		76.9			125.9			137.5			185.2
	Income tax (benefit) provision		(14.1		)	28			38.4			33.4
	Net income		$	91		$	97.9		$	99.1		$	151.8
	Net income per share(3)
	Basic		$	0.18		$	0.19		$	0.2		$	0.3
	Diluted		$	0.18		$	0.19		$	0.19		$	0.3
	_______________________________
	(1)	In the second quarter of 2013, the Company extended the useful lives of certain computers and equipment based on actual historical usage, which demonstrated longer useful lives, as well as the planned use of these assets. The change was accounted for as a change in estimate and applied prospectively. This change in accounting estimate decreased depreciation expense within research and development expense by approximately $11.0 million or $0.01 per diluted share for the second quarter of 2013, $9.4 million or $0.01 for the third quarter of 2013, and $7.9 million or $0.01 for the fourth quarter of 2013.
	(2)	In the third quarter of 2013, the Company implemented the 2013 Restructuring Plan for workforce reductions, contract terminations, and project cancellations and recorded restructuring charges of $7.4 million and $3.7 million to operating expenses and cost of revenues, respectively. In the fourth quarter of 2013, the Company continued to implement restructuring activities under the 2013 Restructuring Plan and primarily recorded charges to operating expenses of $17.6 million.
	(3)	Net income per share is computed independently. Therefore, the sum of the quarterly net income per share may not equal the total computed for the year or any cumulative interim period.
	(4)	Certain amounts in the prior quarters' Condensed Consolidated Statements of Operations have been reclassified to conform to the current year presentation.

Subsequent_Events_Notes

Subsequent Events (Notes)	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events
	Dividend Declaration
	On January 27, 2015, the Company announced that it had declared a quarterly cash dividend of $0.10 per share of common stock payable on March 24, 2015 to stockholders of record as of the close of business on March 3, 2015.
	Stock Repurchase Activities
	Subsequent to December 31, 2014, through the filing of this Report, the Company repurchased 10.9 million shares of its common stock, for an aggregate purchase price of $248.1 million at an average price of $22.75 per share, under the 2014 Stock Repurchase Program and were settled prior to the filing of this Report. Under the 2014 Stock Repurchase Program, the Company has $926.9 million authorized funds remaining as of the filing date.

Schedule_II_Valuation_and_Qual

Schedule II- Valuation and Qualifying Account	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Account
	Allowance for Doubtful Accounts	Balance at		Charged to			Write-offs,			Balance at
		Beginning of		(Reversed from)			Net of			End of
		Year		Costs and			Recoveries			Year
				Expenses
	2014	$	5.4	$	(0.7	)	$	—		$	4.7
	2013	$	9.5	$	(3.8	)	$	(0.3	)	$	5.4
	2012	$	9.5	$	0.1		$	(0.1	)	$	9.5
				Additions
	Sales Return Reserve	Balance at		Charged as a			Charged to			Used			Balance at
		Beginning of		Reduction in			Other Accounts						End of
		Year		Revenues									Year
	2014	$	49	$	53.2		$	80.9		$	(132.9	)	$	50.2
	2013	$	52.7	$	35		$	61.5		$	(100.2	)	$	49
	2012	$	52	$	40		$	48.6		$	(87.9	)	$	52.7

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates
	The preparation of the financial statements and related disclosures in conformity with U.S. GAAP requires the Company to make judgments, assumptions, and estimates that affect the amounts reported in the Consolidated Financial Statements and the accompanying notes. The Company bases its estimates and assumptions on current facts, historical experience, and various other factors that it believes are reasonable under the circumstances, to determine the carrying values of assets and liabilities that are not readily apparent from other sources. To the extent there are material differences between the Company's estimates and the actual results, the Company's future consolidated results of operation may be affected.
Cash and Cash Equivalents	Cash and Cash Equivalents
	Cash and cash equivalents consist of cash on hand, demand deposits with banks, highly liquid investments in money market funds, commercial paper, government securities, certificates of deposit, and corporate debt securities, which are readily convertible into cash. All highly liquid investments purchased with original maturities of three months or less are classified as cash and cash equivalents.
Investments in Available-for-Sale and Trading Securities	Investments in Available-for-Sale and Trading Securities
	The Company's investments in publicly-traded debt and equity securities are classified as available-for-sale. Available-for-sale investments are initially recorded at cost and periodically adjusted to fair value in the Consolidated Balance Sheets. Unrealized gains and losses on these investments are reported as a separate component of accumulated other comprehensive income. Realized gains and losses are determined based on the specific identification method and are reported in the Consolidated Statements of Operations.
	The Company periodically evaluates its investments to determine if impairment charges are required. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value has been less than the Company's cost basis, the investment's financial condition, and near-term prospects of the investee. If the Company determines that the decline in an investment's fair value is other than temporary, the difference is recognized as an impairment loss in its Consolidated Statements of Operations. The Company's non-qualified compensation plan is invested in mutual funds which are classified as trading securities and reported at fair value in the Consolidated Balance Sheets. The realized and unrealized holding gains and losses are reported in the Consolidated Statements of Operations.
Privately-Held Investments	Privately-Held Investments
	The Company has privately-held investments, which are included in other long-term assets in the Consolidated Balance Sheets. These investments include debt and redeemable preferred stock securities that are carried at fair value, and non-redeemable preferred stock securities that are carried at cost. The investments carried at cost are adjusted for any impairment, as the Company does not have a controlling interest and does not have the ability to exercise significant influence over these companies. These investments are inherently high risk as the market for technologies or products manufactured by these companies are usually in their early stages at the time of the investment by the Company and such markets may never be significant. The Company measures the fair value of privately-held investments using an analysis of the financial conditions and near term prospects of the investees, including recent financing activities and their capital structure. Realized gains and losses, if any, are reported in the Consolidated Statements of Operations.
Fair Value	Fair Value
	Fair value is defined as the price that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value, the Company considers the principal or most advantageous market in which it transacts, and considers assumptions that market participants would use when pricing the asset or liability. The Company applies the following fair value hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement:
	Level 1 – Quoted prices in active markets for identical assets or liabilities.
	Level 2 – Quoted prices for similar assets and liabilities in active markets or inputs that are observable for the asset or liability, either directly or indirectly through market corroboration, for substantially the full term of the financial instrument. These inputs are valued using market based approaches.
	Level 3 – Inputs are unobservable inputs based on the Company’s assumptions. These inputs, if any, are valued using internal financial models.
Derivatives	Derivatives
	The Company uses derivatives to partially offset its market exposure to fluctuations in certain foreign currencies. The Company does not enter into derivatives for speculative or trading purposes.
	The Company uses foreign currency forward or option contracts to hedge certain forecasted foreign currency transactions relating to operating expenses. These derivatives are designated as cash flow hedges. Execution of these cash flow hedge derivatives typically occurs every month with maturities of one year or less. These derivatives are carried at fair value and the effective portion of the derivative's gain or loss is initially reported as a component of accumulated other comprehensive income, and upon occurrence of the forecasted transaction, is subsequently reclassified into the costs of services or operating expense line item to which the hedged transaction relates. The Company records any ineffectiveness of the hedging instruments in other income (expense), net, on its Consolidated Statements of Operations. Cash flows from such hedges are classified as operating activities. All amounts within other comprehensive income are expected to be reclassified into earnings within the next twelve months.
	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 derivatives are carried at fair value with changes recorded in other income (expense), net in the Consolidated Statements of Operations. Changes in the fair value of these derivatives are largely offset by remeasurement of the underlying assets and liabilities. Cash flows from such derivatives are classified as operating activities. These foreign exchange forward contracts have maturities of one year or less.
Inventory	Inventory
	Inventory consists primarily of component parts to be used in the manufacturing process and finished goods in-transit, and is stated at the lower of cost or market. Cost is computed using standard cost, which approximates actual cost, on a first-in, first-out basis. A charge is recorded to cost of product when inventory is determined to be in excess of anticipated demand or considered obsolete. At the point of loss recognition, a new, lower-cost basis for that inventory is established, and subsequent changes in facts and circumstances do not result in the restoration or increase in the newly established cost basis.
Property and Equipment	Property and Equipment
	Property and equipment are recorded at cost less accumulated depreciation. Depreciation is calculated using the straight-line method, over the estimated useful lives of the following assets:
		Estimated Useful Life (years)
	Computers, equipment, and software	3 to 7
	Furniture and fixtures	5
	Building and building improvements	7 to 40
	Land improvements	5 to 40
	Leasehold improvements	Lease term, not to exceed 10 years
	Construction in progress is related to the construction or development of property and equipment that have not yet been placed in service for their intended use. Depreciation for equipment commences once it is placed in service and depreciation for buildings and leasehold improvements commences once they are ready for their intended use.
Goodwill and Other Long-Lived Assets	Goodwill and Other Long-Lived Assets
	Goodwill represents the future economic benefits arising from other assets acquired in a business combination or an acquisition that are not individually identified and separately recorded. The excess of the purchase price over the estimated fair value of net assets of businesses acquired in a business combination is recognized as goodwill. Goodwill is tested for impairment annually during the fourth quarter or more frequently if certain circumstances change that would more likely than not indicate that the fair value of a reporting unit is below its carrying value. An impairment loss is recognized to the extent that the carrying amount of goodwill exceeds the asset's implied fair value. Other intangible assets acquired in a business combination and determined to have an indefinite useful life are not amortized but are assessed for potential impairment annually or when events or circumstances indicate that their carrying amounts might be impaired.
	Long-lived assets, such as property, plant, and equipment, and purchased intangible assets subject to amortization, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset, or asset group, to estimated undiscounted future cash flows expected to be generated by the asset, or asset group. An impairment charge is recognized by the amount by which the carrying amount of the asset, or asset group, exceeds its fair value.
	The Company amortizes intangible assets with estimable useful lives on a straight-line basis over their useful lives.
Revenue Recognition	Revenue Recognition
	Revenue is recognized when all of the following criteria have been met:
	•	Persuasive evidence of an arrangement exists. The Company generally relies upon sales contracts or agreements, and customer purchase orders to determine the existence of an arrangement.
	•	Delivery has occurred. The Company uses shipping terms and related documents, or written evidence of customer acceptance, when applicable, to verify delivery or performance.
	•	Sales price is fixed or determinable. The Company assesses whether the sales price is fixed or determinable based on the payment terms and whether the sales price is subject to refund or adjustment.
	•	Collectability is reasonably assured. The Company assesses collectability based on creditworthiness of customers as determined by its credit checks, their payment histories, or changes in circumstances that indicate that collectability is not reasonably assured.
	When sales arrangements contain multiple elements the Company allocates revenue to each element based on a selling price hierarchy. The selling price for a deliverable is based on either vendor-specific objective evidence (“VSOE”) if available, third-party evidence (“TPE”) if VSOE is not available, or estimated selling price (“ESP”) if neither VSOE nor TPE is available. The Company then recognizes revenue on each deliverable in accordance with its policies for product and service revenue recognition. VSOE of selling price is based on the price charged when the element is sold separately. In determining VSOE, the Company requires that a substantial majority of the selling prices fall within a reasonable range based on historical discounting trends for specific products and services. TPE of selling price is established by evaluating largely interchangeable competitor products or services in stand-alone sales to similar situated customers. However, as the Company's products contain a significant element of proprietary technology and its solutions offer substantially different features and functionality, the comparable pricing of third-party products with similar functionality typically cannot be obtained and therefore TPE is not used. ESP is established considering multiple factors including, but not limited to pricing practices in different geographies and through different sales channels, gross margin objectives, internal costs, competitor pricing strategies, and industry technology lifecycles.
	In multiple element arrangements where software deliverables are included, revenue is allocated to each separate unit of accounting for each of the non-software deliverables and to the software deliverables as a group using the relative selling prices of each of the deliverables in the arrangement based on the aforementioned selling price hierarchy. If the arrangement contains more than one software deliverable, the arrangement consideration allocated to the software deliverables as a group is then allocated to each software deliverable using the residual method when VSOE of fair value of the undelivered items exists. Under the residual method, the amount of revenue allocated to delivered elements equals the total arrangement consideration less the aggregate fair value of any undelivered elements. If VSOE of one or more undelivered items does not exist, revenue from the entire arrangement is deferred and recognized at the earlier of: (i) delivery of those elements or (ii) when fair value can be established unless maintenance services is the only undelivered element, in which case, the entire arrangement fee is recognized ratably over the maintenance service period.
	The Company limits the amount of revenue recognition for delivered elements to the amount that is not contingent on the future delivery of products or services or subject to customer-specific return or refund privileges.
	The Company records reductions to revenue for estimated product returns and pricing adjustments, such as rebates and price protection, in the same period that the related revenue is recorded. The amount of these reductions is based on historical sales returns and price protection credits, specific criteria outlined in rebate agreements, and other factors known at the time.
	A portion of the Company's sales is made through distributors under agreements allowing for pricing credits or rights of return. As reliable estimates of these credits or returns cannot be made, product revenue on sales made through these distributors is recognized upon sell-through as reported by the distributors to the Company. Deferred revenue on shipments to distributors reflects the effects of distributor pricing credits given and the amount of gross margin expected to be realized upon sell-through. Deferred revenue is recorded net of the related product costs of revenue.
	Service revenues include revenue from maintenance, training, and professional services. Maintenance is offered under renewable contracts. Revenue from maintenance service contracts is deferred and recognized ratably over the contractual support period, which is generally one to three years. Revenue from training and professional services is recognized as services are completed or ratably over the contractual period, which is generally one year or less.
Allowance For Doubtful Accounts	Allowance for Doubtful Accounts
	The allowance for doubtful accounts is based on the Company's assessment of the collectability of customer accounts. The Company regularly reviews its receivables that remain outstanding past their applicable payment terms and establishes an allowance by considering factors such as historical experience, credit quality, and age of the accounts receivable balances, and current economic conditions that may affect a customer's ability to pay.
Warranty Reserves	Warranty Reserves
	The Company generally offers a one-year warranty on most of its hardware products, and a 90-day warranty on the media that contains the software embedded in the products. Warranty costs are recognized as part of the Company's cost of sales based on associated material costs, logistics costs, labor costs, and overhead at the time revenue is recognized. Material costs are estimated primarily based upon the historical costs to repair or replace product returns within the warranty period. Labor, logistics and overhead costs are estimated primarily based upon historical trends in the cost to support customer cases within the warranty period.
Contract Manufacturer Liabilities	Contract Manufacturer Liabilities
	The Company establishes a liability for non-cancelable, non-returnable purchase commitments with its contract manufacturers for carrying charges, quantities in excess of its demand forecasts, or obsolete material charges for components purchased by the contract manufacturers to meet the Company’s demand forecast or customer orders. The demand forecasts are based upon historical trends and analysis from the Company's sales and marketing organizations, adjusted for overall market conditions.
Research and Development Expense	Research and Development
	Costs to research, design, and develop the Company's products are expensed as incurred.
Software Development Costs	Software Development Costs
	Capitalization of software development costs for software to be sold, leased, or otherwise marketed begins when a product's technological feasibility has been established and ends when a product is available for general release to customers. Generally, the Company's products are released soon after technological feasibility has been established. As a result, costs incurred between achieving technological feasibility and product general availability have not been significant.
	The Company capitalizes costs associated with internal-use software systems that have reached the application development stage and are primarily attributable to the Company's enterprise resource planning ("ERP") implementation. Such capitalized costs include external direct costs utilized in developing or obtaining the applications and payroll and payroll-related costs for employees, who are directly associated with the development of the applications.
Advertising	Advertising
	Advertising costs are charged to sales and marketing expense as incurred. Advertising expense was $19.2 million, $20.1 million, and $20.0 million, for 2014, 2013, and 2012, respectively.
Foreign Currency	Foreign Currency
	Assets and liabilities of foreign operations with non-U.S. Dollar functional currency are translated to U.S. Dollars using exchange rates in effect at the end of the period. Revenue and expenses are translated to U.S. Dollars using average exchange rates for the period. The resulting translation adjustments are included in the Company’s Consolidated Balance Sheets in the stockholders’ equity section as a component of accumulated other comprehensive income. For the Company’s international subsidiaries in which the functional currency is the U.S. dollar, the Company records foreign exchange gains and losses for assets and liabilities denominated in non-US dollar currencies. These remeasurement adjustments are recorded in other income (expense), net in the Consolidated Statements of Operations.
Loss Contingencies	Loss Contingencies
	The Company is subject to the possibility of various loss contingencies arising in the ordinary course of business. Management considers the likelihood of loss related to an asset, or the incurrence of a liability, as well as its ability to reasonably estimate the amount of loss, in determining loss contingencies. An estimated loss contingency is accrued when it is probable that an asset has been impaired or a liability has been incurred and the amount of loss can be reasonably estimated. The Company regularly evaluates current information available to determine whether such accruals should be adjusted and whether new accruals are required.
Share-Based Compensation	Share-Based Compensation
	The Company measures and recognizes compensation cost for all share-based awards made to employees and directors, including employee stock options, stock awards, stock units, and employee stock purchases related to the Employee Stock Purchase Plan ("ESPP"). Share-based compensation expense is based on the fair value of the underlying awards and amortized on a straight-line basis, net of estimated forfeitures.
	The Company utilizes the Black-Scholes-Merton (“BSM”) option-pricing model to estimate the fair value of its stock options and Employee Stock Purchase Plan ("ESPP") shares. The BSM model requires various highly subjective assumptions that represent management's best estimates of volatility, risk-free interest rate, expected life, and dividend yield. The Company estimates expected volatility based on the implied volatility of market-traded options, on the Company's common stock, adjusted for other relevant factors including historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected life of the Company’s stock options and ESPP. The expected life of a stock option is based on historical experience of employee exercises and post-vesting termination behavior as well as the potential effect from options that have not been exercised. The expected life of ESPP approximates the offering period.
	The Company determines the fair value of its restricted stock units ("RSUs"), restricted stock awards ("RSAs"), and performance share awards ("PSAs") based on the closing market price of the Company’s common stock on the date of grant, adjusted by the present value of the expected dividend.
	For market-based RSUs, the Company estimates the fair value and derived service period using the Monte Carlo simulation option pricing model ("Monte Carlo model"). The determination of the grant date fair value and derived service periods using the Monte Carlo model is affected by our stock price as well as various highly subjective assumptions that represent management's best estimates of volatility, risk-free interest rate, and dividend yield. The Company estimates expected volatility based on the implied volatility of market-traded options, on the Company's common stock, adjusted for other relevant factors including historical volatility of the Company’s common stock over the contractual life of the Company's market-based RSUs.
Provision for Income Taxes	Provision for Income Taxes
	Deferred tax assets and liabilities are recognized for the expected tax consequences of temporary differences between the tax bases of assets and liabilities and their reported amounts. Valuation allowances are recorded to reduce deferred tax assets to the amount that will more likely than not be realized.
	The Company accounts for uncertainty in income taxes using a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon settlement. The Company classifies the liability for unrecognized tax benefits as current to the extent that the Company anticipates payment (or receipt) of cash within one year. Interest and penalties related to uncertain tax positions are recognized in the provision for income taxes.
Concentrations of Risk	Concentrations of Risk
	Financial instruments that subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, investments, and accounts receivable. The Company invests only in high-quality credit instruments and maintains its cash, cash equivalents and available-for-sale investments in fixed income securities with several high-quality institutions. Deposits held with banks, including those held in foreign branches of global banks, may exceed the amount of insurance provided on such deposits. These deposits may be redeemed upon demand and, therefore, bear minimal credit risk.
	The Company’s derivatives expose it to credit risk to the extent that counterparties may be unable to meet the terms of the agreement. To mitigate concentration of risk related to its derivatives, the Company establishes counterparty limits to major credit-worthy financial institutions. In addition, the potential risk of loss with any one counterparty resulting from this type of credit risk is monitored and the derivatives transacted with these entities are relatively short in duration. Therefore, the Company does not expect material losses as a result of defaults by counterparties.
	Generally, credit risk with respect to accounts receivable is diversified due to the number of entities comprising the Company's customer base and their dispersion across different geographic locations throughout the world. The Company performs ongoing credit evaluations of its customers and generally does not require collateral on accounts receivable. During the years ended December 31, 2014 and December 31, 2013, no single customer accounted for 10% or more of net revenues. During the year ended December 31, 2012, Verizon Communications, Inc. ("Verizon") accounted for 10.3% of net revenues.
	The Company relies on sole suppliers for certain of its components such as application-specific integrated circuits ("ASICs") and custom sheet metal. Additionally, the Company relies primarily on a limited number of significant independent contract manufacturers and outside design manufacturers for the production of its products. The inability of any supplier or manufacturer to fulfill supply requirements of the Company could negatively impact future operating results.
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	In January 2015, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2015-01 (Subtopic 225-20) - Income Statement - Extraordinary and Unusual Items, which eliminates the concept of extraordinary items. ASU 2015-01 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted. The adoption of this standard is not expected to have an impact on the Company's Consolidated Financial Statements.
	In December 2014, the FASB issued ASU No. 2014-17 (Topic 805) - Business Combinations, which provides an acquired entity with an option to apply pushdown accounting in its separate financial statements upon occurrence of an event in which an acquirer obtains control of the acquired entity. ASU 2014-17 is effective on November 18, 2014. The adoption of this standard is not expected to have an impact on the Company's Consolidated Financial Statements.
	In November 2014, the FASB issued ASU No. 2014-16 (Topic 815) - Derivatives and Hedging, which provides clarification on how current guidance should be interpreted in evaluating the economic characteristics and risks of a host contract in a hybrid financial instrument that is issued in the form of a share. Specifically, the amendments clarify that an entity should consider all relevant terms and features in evaluating the host contract and that no single term or feature would necessarily determine the economic characteristics and risks of the host contract ASU 2014-16 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2015. The amendment should be applied on a modified retrospective basis to existing hybrid financial instruments issued in the form of a share as of the beginning of the year for which the amendments are effective. Early adoption is permitted. The adoption of this standard is not expected to have a material impact on the Company's Consolidated Financial Statements.
	In August 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-15 (Subtopic 205-40) - Presentation of Financial Statements—Going Concern: Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern ("ASU 2014-15") which provides guidance about management's responsibility to evaluate whether or not there is substantial doubt about the Company's ability to continue as a going concern and to provide related footnote disclosure. ASU 2014-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. Early application is permitted. The adoption of this standard is not expected to have an impact on the Company's Consolidated Financial Statements.
	In June 2014, the FASB issued ASU No. 2014-12 (Topic 718) - Compensation - Stock Compensation ("ASU 2014-12") which provides guidance that a performance target that affects vesting of a share-based payment and that could be achieved after the requisite service period is a performance condition. As a result, the target is not reflected in the estimation of the award’s grant date fair value. Compensation cost for such an award would be recognized over the required service period, if it is probable that the performance condition will be achieved. ASU 2014-12 is effective for all entities for annual periods beginning after December 15, 2015 and interim periods within those annual periods. ASU 2014-12 should be applied on a prospective basis to awards that are granted or modified on or after the effective date. The adoption of this standard is not expected to have an impact on the Company's Consolidated Financial Statements.
	In May 2014, the FASB issued ASU No. 2014-09 (Topic 606)—Revenue from Contracts with Customers ("ASU 2014-09") which provides guidance for revenue recognition. This ASU affects all contracts that the Company enters into with customers to transfer goods and services or for the transfer of nonfinancial assets. This ASU will supersede the revenue recognition requirements in Topic 605, and most industry specific guidance. This ASU also supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition-Construction-Type and Production-Type Contracts. The standard's core principle is that revenue is recognized when promised goods or services are transferred to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. In doing so, the Company will need to use additional judgment and estimates than under the existing guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 is effective for annual and interim periods beginning after December 15, 2016. Early adoption is not permitted. Accordingly, the ASU will be effective for the Company beginning fiscal year 2017. The Company is currently evaluating the impact of the adoption on its Consolidated Financial Statements.
	In April 2014, the FASB issued ASU No. 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity ("ASU 2014-08") which raises the threshold for a disposal to qualify as a discontinued operation and requires new disclosures of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. ASU 2014-08 is effective for annual periods beginning on or after December 15, 2014. Early adoption is permitted but only for disposals that have not been reported in financial statements previously issued. The Company has determined that this pronouncement would not have a material impact on the Company's financial position or results of operations.

Significant_Accounting_Policie2

Significant Accounting Policies Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Property and equipment useful life	Depreciation is calculated using the straight-line method, over the estimated useful lives of the following assets:
		Estimated Useful Life (years)
	Computers, equipment, and software	3 to 7
	Furniture and fixtures	5
	Building and building improvements	7 to 40
	Land improvements	5 to 40
	Leasehold improvements	Lease term, not to exceed 10 years

Business_Combinations_Tables

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2014									Dec. 31, 2012
Business Combinations [Abstract]
Schedule of purchase consideration allocation for acquisitions	The following table presents the purchase consideration allocations for these acquisitions based upon acquisition-date fair values, including cash and cash equivalents acquired (in millions):
		2014 Acquisitions				2013 Acquisitions		2012 Acquisitions
	Net tangible assets acquired	$	—			$	0.1	$	3.5
	Net liabilities acquired	(2.7		)		—		—
	Intangible assets acquired	17.8				9.9		54.1
	Goodwill	13.6				—		129.7
	Total	$	28.7			$	10	$	187.3
Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination	The following table presents details of the Company's intangible assets acquired through the business combination completed during the twelve months ended December 31, 2014 (in millions, except years):									The following table presents details of the intangible assets acquired for the business combinations completed during 2012 as of their respective acquisition dates (in millions, except years):
		Weighted		Amount							Contrail			Mykonos			BitGravity
		Average									Weighted	Amount		Weighted	Amount		Weighted	Amount
		Estimated									Average			Average			Average
		Useful									Estimated			Estimated			Estimated
		Life									Useful			Useful			Useful
		(In Years)									Life			Life			Life
	Existing technology	7		$	10.7						(In Years)			(In Years)			(In Years)
										Existing technology	—	$	—	6	$	19.3	3	$	12.4
	Customer relationships	7		6
										Trade name and trademarks	—	—		7	1		—	—
	Trade name	4		0.6
										In-process research and development	N/A	17.4		N/A	4		—	—
	Backlog	1		0.2
										Total	—	$	17.4	6	$	24.3	3	$	12.4
	Non-compete agreements	2		0.3
	Total	7		$	17.8

Cash_Equivalents_and_Investmen1

Cash Equivalents and Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Cash Equivalents and Investments [Abstract]
Investments in available-for-sale and trading securities	The following tables summarize the Company's unrealized gains and losses and fair value of investments designated as available-for-sale and trading securities as of December 31, 2014 and December 31, 2013 (in millions):
		Amortized		Gross Unrealized			Gross Unrealized			Estimated Fair
		Cost		Gains			Losses			Value
	As of December 31, 2014
	Fixed income securities:
	Asset-backed securities	$	269.3	$	—		$	(0.3	)	$	269
	Certificates of deposit	10.6		—			—			10.6
	Commercial paper	20.3		—			—			20.3
	Corporate debt securities	738.6		0.5			(1.1		)	738
	Foreign government debt securities	24.6		—			—			24.6
	Government-sponsored enterprise obligations	162.2		—			(0.1		)	162.1
	U.S. government securities	246.1		—			(0.1		)	246
	Total fixed income securities	1,471.70		0.5			(1.6		)	1,470.60
	Money market funds	594.2		—			—			594.2
	Mutual funds	3.9		0.1			—			4
	Publicly-traded equity securities	2.1		—			(0.1		)	2
	Total available-for-sale securities	2,071.90		0.6			(1.7		)	2,070.80
	Trading securities in mutual funds(1)	16.3		—			—			16.3
	Total	$	2,088.20	$	0.6		$	(1.7	)	$	2,087.10
	Reported as:
	Cash equivalents	$	576.6	$	—		$	—		$	576.6
	Restricted investments	45.2		—			—			45.2
	Short-term investments	332.2		0.2			(0.2		)	332.2
	Long-term investments	1,134.20		0.4			(1.5		)	1,133.10
	Total	$	2,088.20	$	0.6		$	(1.7	)	$	2,087.10
	________________________________
	-1	Balance includes the Company's non-qualified deferred compensation plan assets.
		Amortized		Gross Unrealized			Gross Unrealized			Estimated Fair
		Cost		Gains			Losses			Value
	As of December 31, 2013
	Fixed income securities:
	Asset-backed securities	$	249.9	$	0.1		$	(0.1	)	$	249.9
	Certificates of deposit	27.6		—			—			27.6
	Commercial paper	6.9		—			—			6.9
	Corporate debt securities	813.6		2			(0.3		)	815.3
	Foreign government debt securities	10.7		—			—			10.7
	Government-sponsored enterprise obligations	306.2		0.1			(0.1		)	306.2
	U.S. government securities	303.3		0.1			(0.1		)	303.3
	Total fixed income securities	1,718.20		2.3			(0.6		)	1,719.90
	Money market funds	1,043.70		—			—			1,043.70
	Mutual funds	3.9		0.1			—			4
	Publicly-traded equity securities	12		104.5			(1.9		)	114.6
	Total available-for-sale securities	2,777.80		106.9			(2.5		)	2,882.20
	Trading securities in mutual funds(1)	15.4		—			—			15.4
	Total	$	2,793.20	$	106.9		$	(2.5	)	$	2,897.60
	Reported as:
	Cash equivalents	$	996.2	$	—		$	—		$	996.2
	Restricted investments	87.5		0.1			—			87.6
	Short-term investments	459		104.9			(2.0		)	561.9
	Long-term investments	1,250.50		1.9			(0.5		)	1,251.90
	Total	$	2,793.20	$	106.9		$	(2.5	)	$	2,897.60
	_______________________________
	-1	Balance includes the Company's non-qualified deferred compensation plan assets.
Maturities of fixed income securities	The following table presents the contractual maturities of the Company's total fixed income securities as of December 31, 2014 (in millions):
		Amortized		Gross Unrealized			Gross Unrealized			Estimated Fair
		Cost		Gains			Losses			Value
	Due in less than one year	$	337.5	$	0.1		$	(0.2	)	$	337.4
	Due between one and five years	1,134.20		0.4			(1.4		)	1,133.20
	Total	$	1,471.70	$	0.5		$	(1.6	)	$	1,470.60
Available-for-sale investments in an unrealized loss position	The following tables present the Company's available-for-sale securities that were in an unrealized loss position as of December 31, 2014 and December 31, 2013 (in millions):
		Less than 12 Months					12 Months or Greater					Total
		Fair		Unrealized			Fair			Unrealized		Fair		Unrealized
		Value		Loss			Value			Loss		Value		Loss
	As of December 31, 2014
	Fixed income securities:
	Asset-backed securities	$	221.9	$	(0.3	)	$	—		$	—	$	221.9	$	(0.3	)
	Corporate debt securities	515.9		(1.1		)	—			—		515.9		(1.1		)
	Foreign government debt securities(1)	24.6		—			—			—		24.6		—
	Government-sponsored enterprise obligations	113.8		(0.1		)	—			—		113.8		(0.1		)
	U.S. government securities	189		(0.1		)	—			—		189		(0.1		)
	Total fixed income securities	1,065.20		(1.6		)	—			—		1,065.20		(1.6		)
	Publicly-traded equity securities	2		(0.1		)	—			—		2		(0.1		)
	Total available-for sale securities	$	1,067.20	$	(1.7	)	$	—		$	—	$	1,067.20	$	(1.7	)
	________________________________
	(1) Balances less than 12 months include investments that were in an immaterial unrealized loss position as of December 31, 2014.
		Less than 12 Months					12 Months or Greater					Total
		Fair		Unrealized			Fair			Unrealized		Fair		Unrealized
		Value		Loss			Value			Loss		Value		Loss
	As of December 31, 2013
	Fixed income securities:
	Asset-backed securities(1)	$	153	$	(0.1	)	$	0.6		$	—	$	153.6	$	(0.1	)
	Corporate debt securities(1)	156.1		(0.3		)	9.7			—		165.8		(0.3		)
	Foreign government debt securities(2)	10		—			—			—		10		—
	Government-sponsored enterprise obligations	123.1		(0.1		)	—			—		123.1		(0.1		)
	U.S. government securities	119.7		(0.1		)	—			—		119.7		(0.1		)
	Total fixed income securities	561.9		(0.6		)	10.3			—		572.2		(0.6		)
	Publicly-traded equity securities	6.8		(1.9		)	—			—		6.8		(1.9		)
	Total available-for-sale securities	$	568.7	$	(2.5	)	$	10.3		$	—	$	579	$	(2.5	)
	________________________________
	(1)	Balances 12 months or greater include investments that were in an immaterial unrealized loss position as of December 31, 2013.
	(2)	Balances less than 12 months include investments that were in an immaterial unrealized loss position as of December 31, 2013.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables provide a summary of assets and liabilities measured at fair value on a recurring basis and as reported in the Consolidated Balance Sheets (in millions):
		Fair Value Measurements at December 31, 2014 Using:
		Quoted Prices in		Significant Other			Significant Other
		Active Markets For		Observable			Unobservable
		Identical Assets		Remaining Inputs			Remaining Inputs
		(Level 1)		(Level 2)			(Level 3)		Total
	Assets measured at fair value:
	Available-for-sale securities:
	Asset-backed securities	$	—	$	269		$	—	$	269
	Certificates of deposit	—		10.6			—		10.6
	Commercial paper	—		20.3			—		20.3
	Corporate debt securities	—		738			—		738
	Foreign government debt securities	—		24.6			—		24.6
	Government-sponsored enterprise obligations	—		162.1			—		162.1
	Money market funds (1)	594.2		—			—		594.2
	Mutual funds (2)	4		—			—		4
	Publicly-traded equity securities	2		—			—		2
	U.S. government securities	246		—			—		246
	Total available-for-sale securities	846.2		1,224.60			—		2,070.80
	Trading securities in mutual funds (3)	16.3		—			—		16.3
	Privately-held debt securities	—		—			47.5		47.5
	Derivative assets:
	Foreign exchange contracts	—		0.1			—		0.1
	Total assets measured at fair value	$	862.5	$	1,224.70		$	47.5	$	2,134.70
	Liabilities measured at fair value:
	Derivative liabilities:
	Foreign exchange contracts	$	—	$	(3.9	)	$	—	$	(3.9	)
	Total liabilities measured at fair value	$	—	$	(3.9	)	$	—	$	(3.9	)
	Total assets measured at fair value, reported as:
	Cash equivalents	$	552.9	$	23.7		$	—	$	576.6
	Restricted investments	45.2		—			—		45.2
	Short-term investments	87		245.2			—		332.2
	Long-term investments	177.4		955.7			—		1,133.10
	Prepaid expenses and other current assets	—		0.1			—		0.1
	Other long-term assets	—		—			47.5		47.5
	Total assets measured at fair value	$	862.5	$	1,224.70		$	47.5	$	2,134.70
	Total liabilities measured at fair value, reported as:
	Other accrued liabilities	$	—	$	(3.9	)	$	—	$	(3.9	)
	Total liabilities measured at fair value	$	—	$	(3.9	)	$	—	$	(3.9	)
	________________________________
	(1)	Balance includes $41.3 million of restricted investments measured at fair market value, related to the Company's D&O trust and acquisitions related escrows.
	(2)	Balance relates to the restricted investments measured at fair market value of the Company's India Gratuity Trust.
	(3)	Balance relates to the investments measured at fair value related to the Company's non-qualified deferred compensation plan assets.
		Fair Value Measurements at December 31, 2013 Using:
		Quoted Prices in		Significant Other			Significant Other
		Active Markets For		Observable			Unobservable
		Identical Assets		Remaining Inputs			Remaining Inputs
		(Level 1)		(Level 2)			(Level 3)		Total
	Assets measured at fair value:
	Available-for-sale securities:
	Asset-backed securities	$	—	$	249.9		$	—	$	249.9
	Certificates of deposit	—		27.6			—		27.6
	Commercial paper	—		6.9			—		6.9
	Corporate debt securities	—		815.3			—		815.3
	Foreign government debt securities	—		10.7			—		10.7
	Government-sponsored enterprise obligations	—		306.2			—		306.2
	Money market funds (1)	1,043.70		—			—		1,043.70
	Mutual funds (2)	4		—			—		4
	Publicly-traded equity securities	114.6		—			—		114.6
	U.S. government securities	197.2		106.1			—		303.3
	Total available-for-sale securities	1,359.50		1,522.70			—		2,882.20
	Trading securities in mutual funds (3)	15.4		—			—		15.4
	Privately-held debt securities	—		—			28.1		28.1
	Derivative assets:
Foreign exchange contracts	—		3			—		3
Total assets measured at fair value	$	1,374.90	$	1,525.70		$	28.1	$	2,928.70
Liabilities measured at fair value:
Derivative liabilities:
Foreign exchange contracts	$	—	$	(0.7	)	$	—	$	(0.7	)
Total liabilities measured at fair value	$	—	$	(0.7	)	$	—	$	(0.7	)
Total assets measured at fair value, reported as:
Cash equivalents	$	965.1	$	31.1		$	—	$	996.2
Restricted investments	87.6		—			—		87.6
Short-term investments	246.5		315.4			—		561.9
Long-term investments	75.7		1,176.20			—		1,251.90
Prepaid expenses and other current assets	—		3			—		3
Other long-term assets	—		—			28.1		28.1
Total assets measured at fair value	$	1,374.90	$	1,525.70		$	28.1	$	2,928.70
Total liabilities measured at fair value, reported as:
Other accrued liabilities	$	—	$	(0.7	)	$	—	$	(0.7	)
Total liabilities measured at fair value	$	—	$	(0.7	)	$	—	$	(0.7	)
_______________________________
(1)	Balance includes $83.6 million of restricted investments measured at fair market value, related to the Company's D&O trust and acquisition related escrows.
(2)	Balance relates to the restricted investments measured at fair market value of the Company's India Gratuity Trust.
(3)	Balance relates to the investments measured at fair value related to the Company's non-qualified deferred compensation plan assets.

Derivative_Instruments_Tables

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments	The notional amount of the Company's foreign currency derivatives are summarized as follows (in millions):
		As of December 31,
		2014		2013
	Cash flow hedges	$	160.7	$	137.6
	Non-designated derivatives	78		144.4
	Total	$	238.7	$	282

Goodwill_and_Purchased_Intangi1

Goodwill and Purchased Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	The following table presents the goodwill activity (in millions):
		Total
	December 31, 2012	$	4,057.80
	Foreign currency translation adjustment	(0.1		)
	December 31, 2013	4,057.70
	Additions due to business combination	13.6
	Impairment	(850.0		)
	Divestiture	(239.8		)
	31-Dec-14	$	2,981.50
Purchased Intangible Assets	The Company’s purchased intangible assets were as follows (in millions):
		Gross			Accumulated			Impairments and			Net
					Amortization			Other Charges
	As of December 31, 2014
	Intangible assets with finite lives:
	Technologies and patents	$	567.7		$	(466.1	)	$	(49.9	)	$	51.7
	Customer contracts, support agreements, and	78.1			(65.2		)	(2.8		)	10.1
	related relationships
	Other	1.1			(0.5		)	—			0.6
	Total purchased intangible assets	$	646.9		$	(531.8	)	$	(52.7	)	$	62.4
	As of December 31, 2013
	Intangible assets with finite lives:
	Technologies and patents	$	581.4		$	(453.4	)	$	(30.5	)	$	97.5
	Customer contracts, support agreements, and	74.3			(62.7		)	(2.2		)	9.4
	related relationships
	Total purchased intangible assets	$	655.7		$	(516.1	)	$	(32.7	)	$	106.9
Schedule of Intangible Assets Amortization Included in Consolidated Statements of Operations	The following table presents the amortization of intangible assets included in the Consolidated Statements of Operations (in millions):
		Years Ended December 31,
		2014			2013			2012
	Cost of revenues	$	30.9		$	27.3		$	27.6
	Operating expenses:
	Sales and marketing	4.2			3.4			3.5
	General and administrative	1.2			1.2			1.2
	Total operating expenses	5.4			4.6			4.7
	Total	$	36.3		$	31.9		$	32.3
Estimated Future Amortization Expense of Purchased Intangible Assets with Finite Lives	As of December 31, 2014, the estimated future amortization expense of purchased intangible assets with finite lives is as follows (in millions):
	Years Ending December 31,	Amount
	2015	$	24.2
	2016	13.8
	2017	8.9
	2018	5.2
	2019	4.9
	Thereafter	5.4
	Total	$	62.4

Other_Financial_Information_Ta

Other Financial Information (Tables)	12 Months Ended
	Dec. 31, 2014
Other Financial Information [Abstract]
Inventories	Total inventories consisted of the following (in millions):
		As of December 31,
		2014			2013
	Production materials	$	38.3		$	51.3
	Finished goods	24.2			1.4
	Inventories	$	62.5		$	52.7
Property and equipment	Property and equipment, net, consisted of the following (in millions):
		As of December 31,
		2014			2013
	Computers and equipment	$	806.1		$	794.6
	Software	161.2			108.4
	Leasehold improvements	179.5			202.6
	Furniture and fixtures	33.7			42.5
	Building and building improvements	238.4			242.6
	Land and land improvements	241			238.9
	Construction-in-process	70.3			79.5
	Property and equipment, gross	1,730.20			1,709.10
	Accumulated depreciation	(825.9		)	(826.8		)
	Property and equipment, net	$	904.3		$	882.3
Other long-term assets	Other long-term assets consisted of the following (in millions):
		As of December 31,
		2014			2013
	Privately-held investments	$	89.9		$	57.2
	Licensed software	8.6			90.4
	Federal income tax receivable	20			20
	Customer financing receivable	16.9			19.9
	Inventory	8			15.2
	Prepaid costs, deposits, and other	35.5			31.1
	Promissory note in connection with the sale of Junos Pulse(1)	125			—
	Other long-term assets	$	303.9		$	233.8
	_______________________________
	(1)	Refer to Other Income (Expense), net below for further information on the promissory note.
Warranties	Changes in the Company’s warranty reserve were as follows (in millions):
		As of December 31,
		2014			2013
	Beginning balance	$	28		$	29.7
	Provisions made during the period, net	28.6			28.8
	Adjustments related to pre-existing warranties	—			(2.1		)
	Actual costs incurred during the period	(27.9		)	(28.4		)
	Ending balance	$	28.7		$	28
Deferred revenue	Details of the Company's deferred revenue, as reported in the Consolidated Balance Sheets, were as follows (in millions):
		As of December 31,
		2014			2013
	Deferred product revenue:
	Undelivered product commitments and other product deferrals	$	180.3		$	184.9
	Distributor inventory and other sell-through items	103.7			118.7
	Deferred gross product revenue	284			303.6
	Deferred cost of product revenue	(58.4		)	(58.6		)
	Deferred product revenue, net	225.6			245
	Deferred service revenue	850.1			824.3
	Total	$	1,075.70		$	1,069.30
	Reported as:
	Current	$	780.8		$	705.8
	Long-term	294.9			363.5
	Total	$	1,075.70		$	1,069.30
Other (expense) income, net	Other income (expense), net consisted of the following (in millions):
		Years Ended December 31,
		2014			2013			2012
	Interest income	$	10		$	8.7		$	11
	Interest expense	(66.9		)	(58.4		)	(52.9		)
	Net gain on legal settlement	196.1			—			—
	Gain on investments	167.9			11.3			26.7
	Gain on sale of Junos Pulse	19.6			—			—
	Other	6.7			(2.0		)	(1.4		)
	Other income (expense), net	$	333.4		$	(40.4	)	$	(16.6	)

Restructuring_and_Other_Charge1

Restructuring and Other Charges (Tables)	12 Months Ended
	Dec. 31, 2014
Restructuring and Related Activities [Abstract]
Summary of restructuring charges	The following table presents restructuring and other charges included in cost of revenues and restructuring and other charges in the Consolidated Statements of Operations under the Company's restructuring plans (in millions):
		Years Ended December 31,
		2014		2013		2012
	Severance	$	52.6	$	22.9	$	36.7
	Facilities	14.4		10		5.8
	Contract terminations and other	2.3		14.6		57.2
	Asset impairments and write-downs	139.2		—		—
	Total	$	208.5	$	47.5	$	99.7
	Reported as:
	Cost of revenues	$	41.5	$	8.4	$	52.9
	Restructuring and other charges	167		39.1		46.8
	Total	$	208.5	$	47.5	$	99.7
Changes in the restructuring liability	The following table provides a summary of changes in the restructuring liability related to the Company's plans during the year ended December 31, 2014 (in millions):
		December 31,		Charges		Cash			Non-cash			December 31,
		2013				Payments			Settlements and			2014
									Other
	Severance	$	5.6	$	52.6	$	(47.4	)	$	(1.4	)	$	9.4
	Facilities	5.1		14.4		(20.2		)	8.1			7.4
	Contract terminations and other	7.1		2.3		(8.3		)	(0.9		)	0.2
	Total	$	17.8	$	69.3	$	(75.9	)	$	5.8		$	17

LongTerm_Debt_and_Financing_Ta

Long-Term Debt and Financing (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Instruments [Abstract]
Long-term Debt	The following table summarizes the Company's long-term debt (in millions, except percentages):
		As of December 31, 2014
		Amount			Effective Interest
					Rates
	Senior notes:
	3.10% fixed-rate notes, due 2016	$	300		3.25	%
	4.60% fixed-rate notes, due 2021	300			4.69	%
	4.50% fixed-rate notes, due 2024	350			4.63	%
	5.95% fixed-rate notes, due 2041	400			6.03	%
	Total senior notes	1,350.00
	Unaccreted discount	(1.0		)
	Total	$	1,349.00

Equity_Tables

Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Repurchase and Retirement of Common Stock and Net Issuances	The following table summarizes the Company's repurchases and retirements of its common stock under its stock repurchase programs and accelerated share repurchase, and repurchases associated with minimum tax withholdings (in millions, except per share amounts):
		Shares			Average price				Amount
		Repurchased			per share				Repurchased
	2014
	Repurchases under stock repurchase program	46.8			$	22.42			$	1,050.00
	Accelerated share repurchase(1)	49.3			$	24.35			$	1,200.00
	Repurchases for tax withholding	0.6			$	19.69			$	12.5
	2013
	Repurchases under stock repurchase program	28.9			$	19.76			$	570.6
	Repurchases for tax withholding	0.4			$	20.23			$	7.2
	2012
	Repurchases under stock repurchase program	35.8			$	18.05			$	645.6
	Repurchases for tax withholding	0.2			$	23.4			$	5
	_______________________________
	(1)	As part of the 2014 Stock Repurchase Program, the Company entered into two separate accelerated share repurchase agreements (collectively, the "ASR") with two financial institutions to repurchase $1.2 billion of the Company's common stock. The Company made an up-front payment of $1.2 billion pursuant to the ASR to repurchase the Company's common stock. The aggregate number of shares ultimately purchased was determined based on a volume weighted average repurchase price, less an agreed upon discount. The shares received with respect to the ASR have been retired. Retired shares return to authorized but unissued shares of common stock.
Schedule of Accumulated Other Comprehensive Income (Loss)	The components of accumulated other comprehensive income, net of related taxes, for the years ended December 31, 2014 and December 31, 2013 were as follows (in millions):
		Unrealized				Unrealized				Foreign			Total
		Gains (Losses)				Gains (Losses)				Currency
		on Available-for-				on Cash Flow				Translation
		Sale Securities(1)				Hedges(2)				Adjustments
	Balance as of December 31, 2012	$	2.1			$	3			$	(0.4	)	$	4.7
	Other comprehensive gain (loss) before reclassifications	65.1				0.7				(3.4		)	62.4
	Amount reclassified from accumulated other	(1.0		)		(1.5		)		—			(2.5		)
	comprehensive income
	Other comprehensive gain (loss)	64.1				(0.8		)		(3.4		)	59.9
	Balance as of December 31, 2013	$	66.2			$	2.2			$	(3.8	)	$	64.6
	Other comprehensive gain (loss) before reclassifications	48.7				(4.1		)		(14.2		)	30.4
	Amount reclassified from accumulated other	(106.5		)		(2.3		)		—			(108.8		)
	comprehensive income
	Other comprehensive loss, net	(57.8		)		(6.4		)		(14.2		)	(78.4		)
	Balance as of December 31, 2014	$	8.4			$	(4.2	)		$	(18.0	)	$	(13.8	)
	________________________________
	(1)	The reclassifications out of accumulated other comprehensive income during the years ended December 31, 2014 and December 31, 2013 for realized gains on available-for-sale securities of $104.3 million and $1.0 million, respectively, are included in other income (expense), net, in the Consolidated Statements of Operations.
	(2)	The reclassifications out of accumulated other comprehensive income during the year ended December 31, 2014 for realized gains on cash flow hedges are included within research and development of $1.4 million, sales and marketing of $0.3 million, and general and administrative of $0.7 million and for realized losses within cost of revenues of $0.1 million for which the hedged transactions relate in the Consolidated Statements of Operations. The reclassifications out of accumulated other comprehensive income during the year ended December 31, 2013 for realized gains on cash flow hedges are included within cost of revenues of $1.1 million and sales and marketing of $4.3 million and for realized losses within research and development of $3.4 million and general and administrative of $0.5 million for which the hedged transactions relate in the Consolidated Statements of Operations.

Employee_Benefit_Plans_Tables

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2014
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 years ended December 31, 2014 (in millions, except for per share amounts and years):
		Outstanding Options
		Number of Shares			Weighted Average				Weighted Average		Aggregate
					Exercise Price				Remaining		Intrinsic
					per Share				Contractual Term		Value
									(In Years)
	Balance as of December 31, 2011	38.6			$	23.98			3.7		$	75.3
	Granted	3.1			22.81
	Assumed(*)	0.9			0.57
	Canceled	(2.8	)		26.64
	Exercised	(3.6	)		11.71
	Expired	(2.1	)		26.97
	Balance as of December 31, 2012	34.1			$	24.13			3.1		$	52.5
	Canceled	(1.3	)		29.56
	Exercised	(5.6	)		15.58
	Expired	(4.1	)		28.35
	Balance as of December 31, 2013	23.1			$	25.15			2.4		$	44.6
	Canceled	(0.6	)		30.15
	Exercised	(5.4	)		19.76
	Expired	(7.2	)		29.11
	Balance as of December 31, 2014	9.9			$	24.87			2		$	24.7
	As of December 31, 2014:
	Vested and expected-to-vest options	9.8			$	25			2		$	23.6
	Exercisable options	9.1			$	25.88			1.7		$	15.9
	_____________________________
	(*)	Stock options assumed in connection with the acquisition of Contrail.
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range	The following table summarizes additional information regarding outstanding and exercisable options as of December 31, 2014:
			Options Outstanding									Options Exercisable
	Range of Exercise Price		Number Outstanding			Weighted Average		Weighted Average				Number	Weighted Average
	(In dollars)		(In millions)			Remaining		Exercise Price				Exercisable	Exercise Price
						Contractual Life		(In dollars)				(In millions)	(In dollars)
						(In years)
	$0.03 - $15.09		1.7			3.6		$	9.58			1.3	$	12.23
	$16.39 - $22.59		1.4			1.5		20.36				1.2	20.34
	$22.74 - $24.61		1.1			2		23.85				0.9	23.81
	$24.73 - 24.73		0.1			0.4		24.73				0.1	24.73
	$25.16- $25.16		1.2			0.2		25.16				1.2	25.16
	$25.19 - $26.90		1			1.3		26.24				1	26.24
	$26.97 - $29.89		1.6			1.8		28.71				1.6	28.7
	$30.01 - $38.93		0.7			2.9		33.57				0.7	33.6
	$40.26 - $40.26		0.7			2.8		40.26				0.7	40.26
	$44.00 - $44.00		0.4			3		44				0.4	44
	$0.03 - $44.00		9.9			2		$	24.87			9.1	$	25.88
Schedule of Nonvested Share Activity	The following table summarizes the Company’s RSU, RSA, and PSA activity and related information as of and for the three years ended December 31, 2014 (in millions, except per share amounts and years):
		Outstanding RSUs, RSAs, and PSAs
		Number of Shares			Weighted Average				Weighted Average		Aggregate
					Grant-Date Fair				Remaining		Intrinsic
					Value per Share				Contractual Term		Value
									(In Years)
	Balance as of December 31, 2011	19.6			$	30.27			1.5		$	400.5
	RSUs granted	9.9			20.79
	RSUs assumed(1)(2)	0.2			22.21
	PSAs granted(3)	2.2			23.07
	RSAs assumed(2)	5.8			19.59
	RSUs vested(8)	(3.1	)		27.04
	PSAs vested(8)	(1.9	)		18.21
	RSAs vested(8)	(0.7	)		19.59
	RSUs canceled	(2.9	)		27.77
	PSAs canceled	(2.3	)		29.71
	Balance as of December 31, 2012	26.8			$	27.76			1.7		$	565
	RSUs granted	10.3			20.32
	PSAs granted(4)	2.2			21.27
	RSUs vested(8)	(6.1	)		26.15
	PSAs vested(8)	(1.1	)		28.52
	RSAs vested(8)	(1.6	)		19.59
	RSUs canceled	(3.4	)		22.99
	PSAs canceled	(1.7	)		29.1
	Balance as of December 31, 2013	25.4			$	23.44			1.1		$	573.5
	RSUs granted(5)(9)	10			22.52
	RSUs assumed(6)	0.4			22.66
	RSAs assumed(6)	0.9			22.66
	PSAs granted(7)(9)	1.4			24.25
	PSAs assumed(6)	0.2			22.66
	RSUs vested(8)	(7.3	)		22.98
	RSAs vested(8)	(1.4	)		19.59
	PSAs vested(8)	(1.1	)		36.19
	RSUs canceled	(4.0	)		21.63
	PSAs canceled	(3.2	)		30.43
	Balance at December 31, 2014	21.3			$	22.05			1.1		$	475
	As of December 31, 2014
	Vested and expected-to-vest RSUs, RSAs,	17.7			$	21.99			1		$	395.2
	and PSAs
	________________________________
	(1)	RSUs assumed in connection with the acquisition of Mykonos
	-2	RSUs and RSAs assumed in connection with the acquisition of Contrail.
	-3	The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee are achieved at target is 0.9 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 2.2 million shares.
	-4	The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee are achieved at target is 1.1 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 2.2 million shares.
	(5)	Includes service-based and market-based RSUs granted under the 2006 Plan according to its terms.
	-6	RSUs, RSAs, and PSAs assumed in connection with the acquisition of WANDL.
	-7	The number of shares subject to PSAs granted represents the aggregate maximum number of shares that may be issued pursuant to the award over its full term. The aggregate number of shares subject to these PSAs that would be issued if performance goals determined by the Compensation Committee are achieved at target is 0.9 million shares. Depending on achievement of such performance goals, the range of shares that could be issued under these awards is 0 to 1.4 million shares.
	-8	Total fair value of RSUs, RSAs, and PSAs vested during 2014, 2013, and 2012 was $210.1 million, $221.5 million, and $132.0 million, respectively.
	-9	On February 20, 2014, the Company announced its intention to initiate a quarterly cash dividend of $0.10 per share of common stock in the third quarter of 2014. As a result of the Company's announcement, the grant date fair value of RSUs and PSAs granted after the announcement date were reduced by the present value of the dividends expected to be paid on the underlying shares of common stock during the requisite and derived service period as these awards are not entitled to receive dividends until vested. The Company paid quarterly cash dividends in the third and fourth quarter of 2014 of $0.10 per share totaling $86.0 million. The declaration and amount of any future cash dividends are at the discretion of the Board of Directors and will depend on the Company's financial performance, economic outlook, and any other relevant considerations.
Shares available for grant	The following table presents the stock activity and the total number of shares available for grant under the 2006 Plan as of December 31, 2014 (in millions):
		Number of Shares
	Balance as of December 31, 2013	49.1
	RSUs and PSAs granted (1)	(24.1	)
	RSUs and PSAs canceled (1)	15
	Options canceled (2)	0.6
	Options expired (2)	7.2
	Balance as of December 31, 2014	47.8
	________________________________
	(1)	RSUs and PSAs with a per share or unit purchase price lower than 100% of the fair market value of the Company's common stock on the day of the grant under the 2006 Plan are counted against shares authorized under the plan as two and one-tenth shares of common stock for each share subject to such award. The number of shares subject to PSAs granted represents the maximum number of shares that may be issued pursuant to the award over its full term.
	(2)	Includes canceled or expired options under the 1996 Plan and the 2000 Plan that expired after May 18, 2006, which become available for grant under the 2006 Plan according to its terms
Schedule Of Share-based Payment Award, Stock Options and Employee Stock Purchase Plan, Valuation Assumptions	The weighted-average assumptions used and the resulting estimates of fair value for stock options, ESPP, and market-based RSUs were as follows:
		Years Ended December 31,
		2014		2013		2012
	Stock Options(1):
	Volatility	—		—		45%
	Risk-free interest rate	—		—		0.70%
	Expected life (years)	—		—		4.2
	Dividend yield	—		—		—
	Weighted-average fair value per share	—		—		$8.47
	ESPP(1):
	Volatility	30%		36%		47%
	Risk-free interest rate	0.10%		0.10%		0.10%
	Expected life (years)	0.5		0.5		0.5
	Dividend yield	0% - 1.8%		—		—
	Weighted-average fair value per share	$5.72		$5.54		$5.53
	Market-based RSUs(2)
	Volatility	36%		—		—
	Risk-free interest rate	1.60%		—		—
	Dividend yield	0% - 2.0%		—		—
	Weighted-average fair value per share	$16.89		—		—
	________________________________
	(1)	The Black-Scholes-Merton option-pricing model is utilized to estimate the fair value of stock options and ESPP.
	(2)	The fair value of market-based RSUs utilizes the Monte Carlo simulation option pricing model. The Company amortizes the fair value of these awards over the derived service period adjusted for estimated forfeitures for each separately vesting tranche of the award. Provided that the derived service is rendered, the total fair value of the market-based RSUs at the date of grant is recognized as compensation expense even if the market condition is not achieved. However, the number of shares that ultimately vest can vary significantly with the performance of the specified market criteria.
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs	se
	Share-based compensation expense associated with stock options, RSUs, RSAs, PSAs, and ESPP was recorded in the following cost and expense categories in the Company's Consolidated Statements of Operations (in millions):
		Years Ended December 31,
		2014				2013				2012
	Cost of revenues - Product	$	5			$	4.7			$	4.6
	Cost of revenues - Service	14.2				15.4				17
	Research and development	134.5				127.6				109.1
	Sales and marketing	60.2				70.9				81.6
	General and administrative	26.1				26				31.1
	Total	$	240			$	244.6			$	243.4
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award	The following table summarizes share-based compensation expense by award type (in millions):
		Years Ended December 31,
		2014				2013				2012
	Stock options	$	14.9			$	31.5			$	58.9
	RSUs, RSAs, and PSAs	209.7				196.8				163.7
	ESPP	15.4				16.3				20.8
	Total	$	240			$	244.6			$	243.4
Schedule of Unrecognized Compensation Cost, Nonvested Awards	The following table presents unrecognized compensation cost, adjusted for estimated forfeitures, recognized over a weighted-average period related to unvested stock options, RSUs, RSAs, and PSAs as of December 31, 2014 (in millions, except years):
		Unrecognized				Weighted Average
		Compensation Cost				Period
						(In Years)
	Stock options	$	11.4			1.3
	RSUs, RSAs, and PSAs	$	257.8			1.7

Segments_Tables

Segments (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Financial information for each segment	The following table presents net revenues by product and service (in millions):
		Years Ended December 31,
		2014		2013		2012
	Routing	$	2,223.90	$	2,318.00	$	2,037.60
	Switching	721.2		638		554.8
	Security	463.6		563.9		669.7
	Total product	3,408.70		3,519.90		3,262.10
	Total service	1,218.40		1,149.20		1,103.30
	Total	$	4,627.10	$	4,669.10	$	4,365.40
Net revenues by geographic region	The Company attributes revenues to geographic region based on the customer’s ship-to location. The following table presents net revenues by geographic region (in millions):
		Years Ended December 31,
		2014		2013		2012
	Americas:
	United States	$	2,410.60	$	2,381.50	$	2,067.50
	Other	219.7		232		218.4
	Total Americas	2,630.30		2,613.50		2,285.90
	Europe, Middle East, and Africa	1,263.30		1,256.90		1,266.30
	Asia Pacific	733.5		798.7		813.2
	Total	$	4,627.10	$	4,669.10	$	4,365.40
Property and equipment by geographic region	The following table presents geographic information for property and equipment, net and purchased intangible assets, net (in millions):
		As of December 31,
		2014		2013
	United States	$	871.7	$	885.6
	International	95		103.6
	Property and equipment, net and purchased intangible assets, net	$	966.7	$	989.2

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Components of income before the provision for income taxes and noncontrolling interest	The components of pretax (loss) income and noncontrolling interest are summarized as follows (in millions):
		Years Ended December 31,
		2014			2013			2012
	Domestic	$	(509.7	)	$	248.7		$	114.1
	Foreign	423.4			276.8			177.4
	Total pretax (loss) income	$	(86.3	)	$	525.5		$	291.5
Schedule of Components of Provision for Income Taxes	The provision for income taxes is summarized as follows (in millions):
		Years Ended December 31,
		2014			2013			2012
	Current provision (benefit):
	Federal	$	180.1		$	(12.9	)	$	94.3
	States	15.2			(5.0		)	8.4
	Foreign	33.7			32.5			37.1
	Total current provision (benefit)	229			14.6			139.8
	Deferred provision (benefit):
	Federal	17.3			51.2			(28.8		)
	States	1.2			(2.7		)	(1.5		)
	Foreign	0.5			22.6			3.5
	Total deferred provision (benefit)	19			71.1			(26.8		)
	Income tax benefits attributable to employee stock plan activity	—			—			(8.0		)
	Total provision (benefit) for income taxes	$	248		$	85.7		$	105
Schedule of Effective Income Tax Rate Reconciliation	The provision for income taxes differs from the amount computed by applying the federal statutory rate to pretax (loss) income as follows (in millions):
		Years Ended December 31,
		2014			2013			2012
	Expected (benefit) provision at 35% rate	$	(30.2	)	$	184		$	102
	State taxes (benefit), net of federal benefit	9.5			(3.6		)	2
	Foreign income at different tax rates	(90.2		)	(37.7		)	(11.6		)
	Research and development credits	(17.1		)	(32.5		)	(0.5		)
	Share-based compensation	25.3			25.6			22.4
	Non-deductible goodwill impairment	297.5			—			—
	Gain on sale of Junos Pulse	75.6			—			—
	Release of valuation allowance	(22.8		)	—			(3.4		)
	Settlement with tax authorities	—			(28.3		)	—
	Domestic production activities	(6.8		)	(26.3		)	—
	Non-deductible compensation	3.2			1.5			0.6
	Equity investment gain on acquisition	—			—			(5.3		)
	Other	4			3			(1.2		)
	Total provision for income taxes	$	248		$	85.7		$	105
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company's deferred tax assets and liabilities are as follows (in millions):
		As of December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss carry-forwards	$	1.3		$	1.1
	Foreign tax credit carry-forwards	69.7			63.4
	Research and other credit carry-forwards	122.5			106.6
	Deferred revenue	104.9			71
	Stock-based compensation	55.8			86.1
	Reserves and accruals not currently deductible	129.8			153.9
	Other	19.8			13.7
	Total deferred tax assets	503.8			495.8
	Valuation allowance	(144.5		)	(155.7		)
	Deferred tax assets, net of valuation allowance	359.3			340.1
	Deferred tax liabilities:
	Property and equipment basis differences	(35.6		)	(3.1		)
	Purchased intangibles	(16.7		)	(10.1		)
	Unremitted foreign earnings	(260.6		)	(258.9		)
	Deferred compensation and other	(5.1		)	(38.7		)
	Other	—			(0.4		)
	Total deferred tax liabilities	(318.0		)	(311.2		)
	Net deferred tax assets	$	41.3		$	28.9
Schedule of Breakdown Between Current and Long-term Deferred Tax Assets and Deferred Tax Liabilities	The breakdown between current and long-term deferred tax assets and deferred tax liabilities are as follows (in millions):
		As of December 31,
		2014			2013
	Current deferred tax assets	$	147		$	79.8
	Long-term deferred tax assets	1.7			2.4
	Long-term deferred tax liabilities	(107.4		)	(53.3		)
	Total net deferred tax assets	$	41.3		$	28.9
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the beginning and ending amount of the Company's total gross unrecognized tax benefits was as follows (in millions):
		Years Ended December 31,
		2014			2013			2012
	Balance at beginning of year	$	137.6		$	136.1		$	132.2
	Tax positions related to current year:
	Additions	62.5			15.8			8.8
	Tax positions related to prior years:
	Additions	0.6			22.6			0.9
	Reductions	—			(2.2		)	—
	Settlements	—			(31.1		)	(1.2		)
	Lapses in statutes of limitations	(1.5		)	(3.6		)	(4.6		)
	Balance at end of year	$	199.2		$	137.6		$	136.1

Net_Income_per_Share_Tables

Net Income per Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Schedule of Calculation of Basic and Diluted Net Income Per Share	The Company computed basic and diluted net (loss) income per share attributable to Juniper Networks common stockholders as follows (in millions, except per share amounts):
		Years Ended December 31,
		2014			2013		2012
	Numerator:
	Net (loss) income	$	(334.3	)	$	439.8	$	186.5
	Denominator:
	Weighted-average shares used to compute basic net income per share	457.4			501.8		520.9
	Dilutive effect of employee stock awards	—			8.5		5.3
	Weighted-average shares used to compute diluted net income	457.4			510.3		526.2
	per share
	Net (loss) income per share attributable to Juniper Networks common
	stockholders:
	Basic	$	(0.73	)	$	0.88	$	0.36
	Diluted	$	(0.73	)	$	0.86	$	0.35
	Anti-dilutive:
	Potential anti-dilutive shares	20.8			13.2		32.3

Commitments_and_Contingencies_1

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	The following table summarizes the Company’s future minimum payments under non-cancelable operating leases for each of the next five years and thereafter as of December 31, 2014 (in millions):
	Years Ending December 31,	Amount
	2015	$	41.2
	2016	30.1
	2017	22
	2018	14.3
	2019	7.5
	Thereafter	22
	Total	$	137.1

Selected_Quarterly_Financial_D1

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Selected Quarterly Financial Information [Abstract]
Schedule of Selected Quarterly Financial Data (Unaudited)	The tables below set forth selected unaudited financial data for each quarter of the two years ended December 31, 2014 (in millions, except per share amounts):
	Year Ended December 31, 2014		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Net revenues:
	Product		$	876		$	929.2		$	809.5		$	794
	Service		294.1			300.3			316.4			307.6
	Total net revenues		1,170.10			1,229.50			1,125.90			1,101.60
	Cost of revenues:
	Product		326.6			359.3			290			310.9
	Service		123.4			122			121.1			115.6
	Total cost of revenues (1)		450			481.3			411.1			426.5
	Gross margin		720.1			748.2			714.8			675.1
	Operating expenses:
	Research and development		264			255.5			253.2			233.5
	Sales and marketing		273.4			258			249.2			243
	General and administrative		74.9			60.6			55			40.6
	Restructuring and other (credit) charges(1)		114			58.2			(15.0		)	9.8
	Impairment of goodwill(2)		—			—			—			850
	Total operating expenses		726.3			632.3			542.4			1,376.90
	Operating (loss) income		(6.2		)	115.9			172.4			(701.8		)
	Other income (expense), net(3)		154.2			178.6			(6.8		)	7.4
	Income (loss) before income taxes		148			294.5			165.6			(694.4		)
	Income tax provision		37.4			73.4			62			75.2
	Net income (loss)		$	110.6		$	221.1		$	103.6		$	(769.6	)
	Net income (loss) per share:(4)
	Basic		$	0.23		$	0.47		$	0.23		$	(1.81	)
	Diluted		$	0.22		$	0.46		$	0.23		$	(1.81	)
	Cash dividends declared per common stock(5)		$	—		$	—		$	0.1		$	0.1
	_______________________________
	(1)	In the first quarter of 2014, the company initiated a 2014 Restructuring Plan, which consisted of $84.7 million asset write-downs, $28.0 million of severance costs, and $0.8 million of contract terminations that were recorded in restructuring and other charges. In addition, the Company recorded inventory write-downs related to the acceleration of the end-of-service life of certain products totaling $8.4 million to cost of revenues. In the second quarter, the Company recorded $9.9 million of severance costs, $37.6 million of facility consolidation and closures, $8.9 million of asset write-downs, and $1.5 million of contract terminations that were recorded to restructuring and other charges. The Company also recorded inventory write-downs of $11.5 million and a charge related to products with contract manufacturers of $2.3 million for acceleration of the end-of-life service of certain products to cost of revenues. In the third quarter, the Company recorded $7.1 million of severance costs, a benefit of $25.0 million of facility consolidation and closures as a result of a lease assignment, and $2.9 million of asset write-downs, that were recorded to restructuring and other (credit) charges. In the fourth quarter, the Company recorded $6.9 million in severance costs, $1.6 million of facility consolidation and closures, and $20.6 million in asset impairment and write-downs.
	(2)	During the fourth quarter of 2014, the Company recorded an $850.0 million goodwill impairment charge related to its Security reporting unit.
	(3)	In the first quarter of 2014, the Company recorded a gain of $163.0 million related to the sale of investments which were converted from privately-held investments to publicly-traded equity upon IPO. In the second quarter, the Company entered into a settlement agreement with PAN, which resulted in a realized gain on legal settlement of $195.3 million, net of legal fees. All such PAN securities were sold in the third quarter, and the Company recorded an additional $0.8 million gain. In the fourth quarter, the Company recorded a gain of $19.6 million on the sale of Junos Pulse.
	(4)	Net income (loss) per share is computed independently. Therefore, the sum of the quarterly net income per share may not equal the total computed for the year or any cumulative interim period.
	(5)	On July 22, 2014 and October 23, 2014 the company declared a quarterly cash dividend of $0.10 per share of common stock to stockholders on record as of the close of business September 2, 2014 and December 2, 2014, respectively.
	Year Ended December 31, 2013		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Net revenues:
	Product		$	781.8		$	863.8		$	900.8		$	973.5
	Service		277.4			286.9			284.8			300.1
	Total net revenues		1,059.20			1,150.70			1,185.60			1,273.60
	Cost of revenues:
	Product		278.2			321.3			325.5			351.6
	Service		110.2			108.9			113.6			118.4
	Total cost of revenues(2)		388.4			430.2			439.1			470
	Gross margin		670.8			720.5			746.5			803.6
	Operating expenses:
	Research and development(1)		262.2			257.7			264.6			258.7
	Sales and marketing(4)		256.1			267.1			269.5			283.2
	General and administrative(4)		58.5			49.2			61.4			48.2
	Restructuring and other charges(2)		7			8			6			18.1
	Total operating expenses		583.8			582			601.5			608.2
	Operating income		87			138.5			145			195.4
	Other expense, net		(10.1		)	(12.6		)	(7.5		)	(10.2		)
	Income before income taxes		76.9			125.9			137.5			185.2
	Income tax (benefit) provision		(14.1		)	28			38.4			33.4
	Net income		$	91		$	97.9		$	99.1		$	151.8
	Net income per share(3)
	Basic		$	0.18		$	0.19		$	0.2		$	0.3
	Diluted		$	0.18		$	0.19		$	0.19		$	0.3
	_______________________________
	(1)	In the second quarter of 2013, the Company extended the useful lives of certain computers and equipment based on actual historical usage, which demonstrated longer useful lives, as well as the planned use of these assets. The change was accounted for as a change in estimate and applied prospectively. This change in accounting estimate decreased depreciation expense within research and development expense by approximately $11.0 million or $0.01 per diluted share for the second quarter of 2013, $9.4 million or $0.01 for the third quarter of 2013, and $7.9 million or $0.01 for the fourth quarter of 2013.
	(2)	In the third quarter of 2013, the Company implemented the 2013 Restructuring Plan for workforce reductions, contract terminations, and project cancellations and recorded restructuring charges of $7.4 million and $3.7 million to operating expenses and cost of revenues, respectively. In the fourth quarter of 2013, the Company continued to implement restructuring activities under the 2013 Restructuring Plan and primarily recorded charges to operating expenses of $17.6 million.
	(3)	Net income per share is computed independently. Therefore, the sum of the quarterly net income per share may not equal the total computed for the year or any cumulative interim period.
	(4)	Certain amounts in the prior quarters' Condensed Consolidated Statements of Operations have been reclassified to conform to the current year presentation.

Description_of_Business_and_Ba1

Description of Business and Basis of Presentation (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
	segment	segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments	1	2

Significant_Accounting_Policie3

Significant Accounting Policies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Significant Accounting Policies [Line Items]
Original maturity of highly liquid investments classified as cash and cash equivalents	3 months
Maturity period of cash flow hedge derivatives	1 year
Maturity period of non designated hedges derivatives	1 year
Contractual period	1 year
Warranty period for hardware products (in years)	1 year
Warranty period for software (in days)	90 days
Advertising expense	$19.20	$20.10	$20
More than likely percentage of being realized upon settlement, tax benefit	50.00%
Liability for unrecognized tax benefits as current	1 year
Sales Revenue, Segment [Member] | Customer Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Number of customers accounting for more than 10% of revenues	0	0
Verizon [Member] | Sales Revenue, Segment [Member] | Customer Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Percent of net revenues			10.30%
Minimum [Member]
Significant Accounting Policies [Line Items]
Contractual support period	1 year
Maximum [Member]
Significant Accounting Policies [Line Items]
Contractual support period	3 years
Computer, Equipment and Software [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life	3 years
Computer, Equipment and Software [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life	7 years
Furniture and fixtures [Member]
Significant Accounting Policies [Line Items]
Useful life	5 years
Building and building Improvements [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life	7 years
Building and building Improvements [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life	40 years
Land Improvements [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Useful life	5 years
Land Improvements [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life	40 years
Leasehold improvements [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Useful life	10 years

Business_Combinations_Purchase

Business Combinations, Purchase Price Allocation (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Goodwill	$2,981.50	$4,057.70	$4,057.80
2014 Acquisitions [Member]
Business Acquisition [Line Items]
Net tangible assets acquired	0
Net tangible liabilities acquired	-2.7
Intangible assets acquired	17.8
Goodwill	13.6
Consideration Transferred	-28.7
2013 Acquisitions [Member]
Business Acquisition [Line Items]
Net tangible assets acquired		0.1
Net tangible liabilities acquired		0
Intangible assets acquired		9.9
Goodwill		0
Consideration Transferred		-10
2012 Acquisitions [Member]
Business Acquisition [Line Items]
Net tangible assets acquired			3.5
Net tangible liabilities acquired			0
Intangible assets acquired			54.1
Goodwill			129.7
Consideration Transferred			($187.30)

Business_Combinations_Intangib

Business Combinations, Intangible Assets Acquired (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2012	Mar. 08, 2012	Dec. 14, 2012	Feb. 13, 2012
WANDL, Inc, [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)	7 years
Intangible assets acquired	$17.80
Business Acquisitions 2012 [Member]
Business Acquisition [Line Items]
Intangible assets acquired		54.1
Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity BitGravity [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)		3 years
Intangible assets acquired		12.4	12.4
Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity Contrail [Member]
Business Acquisition [Line Items]
Intangible assets acquired		17.4		17.4
Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity Mykonos [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)		6 years
Intangible assets acquired		24.3			24.3
In Process Research and Development [Member] | Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity BitGravity [Member]
Business Acquisition [Line Items]
Intangible assets acquired		0
In Process Research and Development [Member] | Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity Contrail [Member]
Business Acquisition [Line Items]
Intangible assets acquired		17.4
In Process Research and Development [Member] | Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity Mykonos [Member]
Business Acquisition [Line Items]
Intangible assets acquired		4
Existing technology [Member] | WANDL, Inc, [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)	7 years
Intangible assets acquired	10.7
Existing technology [Member] | Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity BitGravity [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)		3 years
Intangible assets acquired		12.4
Existing technology [Member] | Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity Contrail [Member]
Business Acquisition [Line Items]
Intangible assets acquired		0
Existing technology [Member] | Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity Mykonos [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)		6 years
Intangible assets acquired		19.3
Customer Relationships [Member] | WANDL, Inc, [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)	7 years
Intangible assets acquired	6
Trade Names [Member] | WANDL, Inc, [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)	4 years
Intangible assets acquired	0.6
Backlog [Member] | WANDL, Inc, [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)	1 year
Intangible assets acquired	0.2
Non-compete Agreements [Member] | WANDL, Inc, [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)	2 years
Intangible assets acquired	0.3
Trade Name and Trademarks [Member] | Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity BitGravity [Member]
Business Acquisition [Line Items]
Intangible assets acquired		0
Trade Name and Trademarks [Member] | Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity Contrail [Member]
Business Acquisition [Line Items]
Intangible assets acquired		0
Trade Name and Trademarks [Member] | Business Acquisitions 2012 [Member] | Business Acquisition Acquired Entity Mykonos [Member]
Business Acquisition [Line Items]
Acquired intangible asset, weighted average estimated useful life (in years)		7 years
Intangible assets acquired		$1

Business_Combinations_Textuals

Business Combinations, Textuals (Details) (USD $)	12 Months Ended			0 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 07, 2014	Dec. 14, 2012	Feb. 13, 2012	Mar. 08, 2012	Dec. 13, 2012
	Acquisition	Acquisition	Acquisition
Business Acquisition [Line Items]
Length of time subsequent to acquisition date may result in changes of additional information	12 months
Number of Businesses Acquired	1	1	3
Goodwill	$2,981.50	$4,057.70	$4,057.80
Privately-held investments	47.5
2014 Acquisitions [Member]
Business Acquisition [Line Items]
Consideration Transferred	28.7
Net tangible assets acquired	0
Intangible assets acquired	17.8
Goodwill	13.6
2013 Acquisitions [Member]
Business Acquisition [Line Items]
Consideration Transferred		10
Net tangible assets acquired		0.1
Intangible assets acquired		9.9
Acquired intangible asset, weighted average estimated useful life (in years)		5 years
Goodwill		0
2012 Acquisitions [Member]
Business Acquisition [Line Items]
Consideration Transferred			187.3
Net tangible assets acquired			3.5
Intangible assets acquired			54.1
Goodwill			129.7
WANDL, Inc, [Member]
Business Acquisition [Line Items]
Intangible assets acquired	17.8
Acquired intangible asset, weighted average estimated useful life (in years)	7 years
WANDL, Inc, [Member] | 2014 Acquisitions [Member]
Business Acquisition [Line Items]
Consideration Transferred				28.7
Percentage of interests acquired				100.00%
Share-based awards assumed, fair value				34.9
Business Acquisition Acquired Entity Contrail [Member] | 2012 Acquisitions [Member]
Business Acquisition [Line Items]
Consideration Transferred					91.7
Intangible assets acquired			17.4		17.4
Percentage of interests acquired, original					12.00%
Percentage of interest acquired, subsequent					100.00%
Net tangible assets acquired					3.6
Cash and cash equivalents acquired					8.6
Goodwill					70.7
Privately-held investments								3
Fair value of equity interest, original					17.7
Remeasurement gain			14.7
Business Acquisition Acquired Entity Mykonos [Member] | 2012 Acquisitions [Member]
Business Acquisition [Line Items]
Percentage of interests acquired						100.00%
Intangible assets acquired			24.3			24.3
Acquired intangible asset, weighted average estimated useful life (in years)			6 years
Net tangible assets acquired						0.2
Goodwill						58.5
Cash paid for business acquisition						82.6
Business Acquisition Acquired Entity BitGravity [Member] | 2012 Acquisitions [Member]
Business Acquisition [Line Items]
Intangible assets acquired			12.4				12.4
Acquired intangible asset, weighted average estimated useful life (in years)			3 years
Net tangible assets acquired							0.1
Goodwill							0.5
Cash paid for business acquisition							$13

Cash_Equivalents_and_Investmen2

Cash Equivalents and Investments - Available for Sale Securities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Available-for-sale securities:
Available-for-sale securities, amortized cost	$2,071.90	$2,777.80
Available-for-sale Securities, gross unrealized gain	0.6	106.9
Available-for-sale securities, gross unrealized loss	-1.7	-2.5
Available-for-sale securities, estimated fair value	2,070.80	2,882.20
Trading securities:
Trading securities, amortized cost	16.3	15.4
Trading securities, gross unrealized gain	0	0
Trading securities, gross unrealized loss	0	0
Trading securities, estimated fair value	16.3	15.4
Available-for-sale and Trading Investments [Abstract]
Total investments, amortized cost	2,088.20	2,793.20
Total investments, gross unrealized gains	0.6	106.9
Total investments, gross unrealized losses	-1.7	-2.5
Total investments, estimated fair value	2,087.10	2,897.60
Cash equivalents [Member]
Available-for-sale and Trading Investments [Abstract]
Total investments, amortized cost	576.6	996.2
Total investments, gross unrealized gains	0	0
Total investments, gross unrealized losses	0	0
Total investments, estimated fair value	576.6	996.2
Restricted investments [Member]
Available-for-sale and Trading Investments [Abstract]
Total investments, amortized cost	45.2	87.5
Total investments, gross unrealized gains	0	0.1
Total investments, gross unrealized losses	0	0
Total investments, estimated fair value	45.2	87.6
Short-term investments [Member]
Available-for-sale and Trading Investments [Abstract]
Total investments, amortized cost	332.2	459
Total investments, gross unrealized gains	0.2	104.9
Total investments, gross unrealized losses	-0.2	-2
Total investments, estimated fair value	332.2	561.9
Long-term investments [Member]
Available-for-sale and Trading Investments [Abstract]
Total investments, amortized cost	1,134.20	1,250.50
Total investments, gross unrealized gains	0.4	1.9
Total investments, gross unrealized losses	-1.5	-0.5
Total investments, estimated fair value	1,133.10	1,251.90
Fixed Income Securities [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	1,471.70	1,718.20
Available-for-sale Securities, gross unrealized gain	0.5	2.3
Available-for-sale securities, gross unrealized loss	-1.6	-0.6
Available-for-sale securities, estimated fair value	1,470.60	1,719.90
Asset-backed securities [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	269.3	249.9
Available-for-sale Securities, gross unrealized gain	0	0.1
Available-for-sale securities, gross unrealized loss	-0.3	-0.1
Available-for-sale securities, estimated fair value	269	249.9
Certificates of deposit [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	10.6	27.6
Available-for-sale Securities, gross unrealized gain	0	0
Available-for-sale securities, gross unrealized loss	0	0
Available-for-sale securities, estimated fair value	10.6	27.6
Commercial Paper [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	20.3	6.9
Available-for-sale Securities, gross unrealized gain	0	0
Available-for-sale securities, gross unrealized loss	0	0
Available-for-sale securities, estimated fair value	20.3	6.9
Corporate debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	738.6	813.6
Available-for-sale Securities, gross unrealized gain	0.5	2
Available-for-sale securities, gross unrealized loss	-1.1	-0.3
Available-for-sale securities, estimated fair value	738	815.3
Foreign government debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	24.6	10.7
Available-for-sale Securities, gross unrealized gain	0	0
Available-for-sale securities, gross unrealized loss	0	0
Available-for-sale securities, estimated fair value	24.6	10.7
Government-sponsored enterprise obligations [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	162.2	306.2
Available-for-sale Securities, gross unrealized gain	0	0.1
Available-for-sale securities, gross unrealized loss	-0.1	-0.1
Available-for-sale securities, estimated fair value	162.1	306.2
US government securities [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	246.1	303.3
Available-for-sale Securities, gross unrealized gain	0	0.1
Available-for-sale securities, gross unrealized loss	-0.1	-0.1
Available-for-sale securities, estimated fair value	246	303.3
Money market funds [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	594.2	1,043.70
Available-for-sale Securities, gross unrealized gain	0	0
Available-for-sale securities, gross unrealized loss	0	0
Available-for-sale securities, estimated fair value	594.2	1,043.70
Mutual funds [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	3.9	3.9
Available-for-sale Securities, gross unrealized gain	0.1	0.1
Available-for-sale securities, gross unrealized loss	0	0
Available-for-sale securities, estimated fair value	4	4
Publicly-traded equity securities [Member]
Available-for-sale securities:
Available-for-sale securities, amortized cost	2.1	12
Available-for-sale Securities, gross unrealized gain	0	104.5
Available-for-sale securities, gross unrealized loss	-0.1	-1.9
Available-for-sale securities, estimated fair value	$2	$114.60

Cash_Equivalents_and_Investmen3

Cash Equivalents and Investments - Maturities of Available for Sale Investments (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Cash Equivalents and Investments [Abstract]
Amortized cost due within one year	$337.50
Gross unrealized gains due within one year	0.1
Gross unrealized losses due within one year	-0.2
Estimated fair value due within one year	337.4
Amortized cost due between one and five years	1,134.20
Gross unrealized gains due between one and five years	0.4
Gross unrealized losses due between one and five years	-1.4
Estimated fair value due between one and five year	1,133.20
Total investments, amortized cost	1,471.70
Total investments, gross unrealized gains	0.5
Total investments, gross unrealized losses	-1.6
Total investments, estimated fair value	$1,470.60

Cash_Equivalents_and_Investmen4

Cash Equivalents and Investments - Unrealized Loss for Trading and Available for Sale Investments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	$1,067.20	$568.70
Unrealized loss, less than 12 months	-1.7	-2.5
Fair value, 12 months or greater	0	10.3
Unrealized loss, 12 months or greater	0	0
Total fair value, Available-for-sale investments in continuous unrealized loss position	1,067.20	579
Total unrealized loss, Available-for-sale investments in continuous unrealized loss position	-1.7	-2.5
Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	1,065.20	561.9
Unrealized loss, less than 12 months	-1.6	-0.6
Fair value, 12 months or greater	0	10.3
Unrealized loss, 12 months or greater	0	0
Total fair value, Available-for-sale investments in continuous unrealized loss position	1,065.20	572.2
Total unrealized loss, Available-for-sale investments in continuous unrealized loss position	-1.6	-0.6
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	221.9	153
Unrealized loss, less than 12 months	-0.3	-0.1
Fair value, 12 months or greater	0	0.6
Unrealized loss, 12 months or greater	0	0
Total fair value, Available-for-sale investments in continuous unrealized loss position	221.9	153.6
Total unrealized loss, Available-for-sale investments in continuous unrealized loss position	-0.3	-0.1
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	515.9	156.1
Unrealized loss, less than 12 months	-1.1	-0.3
Fair value, 12 months or greater	0	9.7
Unrealized loss, 12 months or greater	0	0
Total fair value, Available-for-sale investments in continuous unrealized loss position	515.9	165.8
Total unrealized loss, Available-for-sale investments in continuous unrealized loss position	-1.1	-0.3
Foreign government debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	24.6	10
Unrealized loss, less than 12 months	0	0
Fair value, 12 months or greater	0	0
Unrealized loss, 12 months or greater	0	0
Total fair value, Available-for-sale investments in continuous unrealized loss position	24.6	10
Total unrealized loss, Available-for-sale investments in continuous unrealized loss position	0	0
Government-sponsored enterprise obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	113.8	123.1
Unrealized loss, less than 12 months	-0.1	-0.1
Fair value, 12 months or greater	0	0
Unrealized loss, 12 months or greater	0	0
Total fair value, Available-for-sale investments in continuous unrealized loss position	113.8	123.1
Total unrealized loss, Available-for-sale investments in continuous unrealized loss position	-0.1	-0.1
US government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	189	119.7
Unrealized loss, less than 12 months	-0.1	-0.1
Fair value, 12 months or greater	0	0
Unrealized loss, 12 months or greater	0	0
Total fair value, Available-for-sale investments in continuous unrealized loss position	189	119.7
Total unrealized loss, Available-for-sale investments in continuous unrealized loss position	-0.1	-0.1
Publicly-traded equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value, less than 12 months	2	6.8
Unrealized loss, less than 12 months	-0.1	-1.9
Fair value, 12 months or greater	0	0
Unrealized loss, 12 months or greater	0	0
Total fair value, Available-for-sale investments in continuous unrealized loss position	2	6.8
Total unrealized loss, Available-for-sale investments in continuous unrealized loss position	($0.10)	($1.90)

Cash_Equivalents_and_Investmen5

Cash Equivalents and Investments - Textuals (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Investment	Investment
Cash Equivalents and Investments [Abstract]
Total investments In unrealized loss position	437	178
Available-for-sale securities, gross realized gains	$166.80
Privately-held investments	89.9	57.2
Debt and redeemable preferred stock securities included in privately held investments	47.5
Unrealized gains, privately-held debt securities	15
Unrealized gain on privately held investments		102.7
Other than temporary impairment of privately held equity investments	$1.10	$2.80	$20

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014
Available-for-sale securities:
Available-for-sale securities, estimated fair value	$2,882,200,000	$2,070,800,000
Trading securities:
Trading securities, estimated fair value	15,400,000	16,300,000
Fair Value Measurements (Textuals)
Restricted investments	83,600,000	41,300,000
Fair value of assets transferred from Level 1 to Level 2	287,400,000
Fair value assets transferred to Level 3	0
Asset-backed securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	249,900,000	269,000,000
Certificates of deposit [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	27,600,000	10,600,000
Commercial Paper [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	6,900,000	20,300,000
Corporate debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	815,300,000	738,000,000
Foreign government debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	10,700,000	24,600,000
Government-sponsored enterprise obligations [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	306,200,000	162,100,000
Money market funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	1,043,700,000	594,200,000
Mutual funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	4,000,000	4,000,000
Publicly-traded equity securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	114,600,000	2,000,000
US Government Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	303,300,000	246,000,000
Debt Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	1,719,900,000	1,470,600,000
Fair Value, Measurements, Recurring [Member]
Liabilities measured at fair value:
Other accrued liabilities	-700,000	-3,900,000
Total liabilities measured at fair value	-700,000	-3,900,000
Total assets measured at fair value	2,928,700,000	2,134,700,000
Cash equivalents	996,200,000	576,600,000
Restricted investments	87,600,000	45,200,000
Short-term investments	561,900,000	332,200,000
Long-term investments	1,251,900,000	1,133,100,000
Prepaid expenses and other current assets	3,000,000	100,000
Other long-term assets	28,100,000	47,500,000
Fair Value, Measurements, Recurring [Member] | Foreign exchange contract [Member]
Derivative assets:
Derivative assets measured at fair value on a recurring basis	3,000,000	100,000
Liabilities measured at fair value:
Derivative liabilities:	-700,000	-3,900,000
Fair Value, Measurements, Recurring [Member] | Available-for-sale Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	2,882,200,000	2,070,800,000
Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	249,900,000	269,000,000
Fair Value, Measurements, Recurring [Member] | Certificates of deposit [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	27,600,000	10,600,000
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	6,900,000	20,300,000
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	815,300,000	738,000,000
Fair Value, Measurements, Recurring [Member] | Foreign government debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	10,700,000	24,600,000
Fair Value, Measurements, Recurring [Member] | Government-sponsored enterprise obligations [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	306,200,000	162,100,000
Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	1,043,700,000	594,200,000
Fair Value, Measurements, Recurring [Member] | Mutual funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	4,000,000	4,000,000
Trading securities:
Trading securities, estimated fair value	15,400,000	16,300,000
Fair Value, Measurements, Recurring [Member] | Publicly-traded equity securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	114,600,000	2,000,000
Fair Value, Measurements, Recurring [Member] | US Government Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	303,300,000	246,000,000
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Trading securities:
Privately-held debt securities, estimated fair value	28,100,000	47,500,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities measured at fair value:
Other accrued liabilities	0	0
Total liabilities measured at fair value	0	0
Total assets measured at fair value	1,374,900,000	862,500,000
Cash equivalents	965,100,000	552,900,000
Restricted investments	87,600,000	45,200,000
Short-term investments	246,500,000	87,000,000
Long-term investments	75,700,000	177,400,000
Prepaid expenses and other current assets	0	0
Other long-term assets	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign exchange contract [Member]
Derivative assets:
Derivative assets measured at fair value on a recurring basis	0	0
Liabilities measured at fair value:
Derivative liabilities:	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Available-for-sale Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	1,359,500,000	846,200,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of deposit [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign government debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Government-sponsored enterprise obligations [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	1,043,700,000	594,200,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	4,000,000	4,000,000
Trading securities:
Trading securities, estimated fair value	15,400,000	16,300,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Publicly-traded equity securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	114,600,000	2,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	197,200,000	246,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Trading securities:
Privately-held debt securities, estimated fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities measured at fair value:
Other accrued liabilities	-700,000	-3,900,000
Total liabilities measured at fair value	-700,000	-3,900,000
Total assets measured at fair value	1,525,700,000	1,224,700,000
Cash equivalents	31,100,000	23,700,000
Restricted investments	0	0
Short-term investments	315,400,000	245,200,000
Long-term investments	1,176,200,000	955,700,000
Prepaid expenses and other current assets	3,000,000	100,000
Other long-term assets	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign exchange contract [Member]
Derivative assets:
Derivative assets measured at fair value on a recurring basis	3,000,000	100,000
Liabilities measured at fair value:
Derivative liabilities:	-700,000	-3,900,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Available-for-sale Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	1,522,700,000	1,224,600,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	249,900,000	269,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of deposit [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	27,600,000	10,600,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	6,900,000	20,300,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	815,300,000	738,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign government debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	10,700,000	24,600,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Government-sponsored enterprise obligations [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	306,200,000	162,100,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Trading securities:
Trading securities, estimated fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Publicly-traded equity securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	106,100,000	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Trading securities:
Privately-held debt securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Liabilities measured at fair value:
Other accrued liabilities	0	0
Total liabilities measured at fair value	0	0
Total assets measured at fair value	28,100,000	47,500,000
Cash equivalents	0	0
Restricted investments	0	0
Short-term investments	0	0
Long-term investments	0	0
Prepaid expenses and other current assets	0	0
Other long-term assets	28,100,000	47,500,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign exchange contract [Member]
Derivative assets:
Derivative assets measured at fair value on a recurring basis	0	0
Liabilities measured at fair value:
Derivative liabilities:	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Available-for-sale Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Asset-backed securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Certificates of deposit [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign government debt securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Government-sponsored enterprise obligations [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual funds [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Trading securities:
Trading securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Publicly-traded equity securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Government Securities [Member]
Available-for-sale securities:
Available-for-sale securities, estimated fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Trading securities:
Privately-held debt securities, estimated fair value	28,100,000	47,500,000
Fair Value Measurements (Textuals)
Purchases of privately held investments		$5,000,000

Fair_Value_Measurements_Assets

Fair Value Measurements, Assets and Liabilities Measured On A Nonrecurring Basis (Details) (USD $)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of goodwill	($850)	$0	$0	$0	($850)	$0	$0
Other than temporary impairment of privately held equity investments					-1.1	-2.8	-20
Impairment of intangible assets (excluding goodwill)						0	-5.4
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value promissory note	125				125
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of long term debt	1,395.20				1,395.20	1,023.50
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liability measured at non-recurring basis	0				0	0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of intangible asset subsequent to impairment							0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cost Method Investment, Privately Held Companies [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Privately-held investments measured on nonrecurring basis						2
Other than temporary impairment of privately held equity investments						-2.8
Security [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of goodwill	($850)				($850)

Derivative_Instruments_Details

Derivative Instruments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivative	$238.70	$282
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivative	160.7	137.6
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount of foreign currency derivative	$78	$144.40

Derivative_Instruments_Cash_Fl

Derivative Instruments, Cash Flow Hedges (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Maximum cash flow hedge derivative term	1 year
Foreign exchange contract [Member] | Cash flow hedging [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) on derivative instruments recognized in AOCI	($3.40)	($1)
Gain on derivative instruments recognized in AOCI			7.2
Operating expenses [Member] | Foreign exchange contract [Member] | Cash flow hedging [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) on derivative instruments reclassified out of AOCI	3.4	0.7
Loss on derivative instruments reclassified out of AOCI			$7.50

Derivative_Instruments_NonDesi

Derivative Instruments, Non-Designated Hedges (Details) (Foreign exchange contract [Member], Other (expense) income, net [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Foreign exchange contract [Member] | Other (expense) income, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on non-designated derivatives	($2.40)	$0.90	$1

Goodwill_and_Purchased_Intangi2

Goodwill and Purchased Intangible Assets (Details) (USD $)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
					ReportingUnit
Goodwill [Roll Forward]
Goodwill, beginning of period				$4,057.70	$4,057.70	$4,057.80
Foreign currency translation adjustment						-0.1
Additions due to business combination					13.6
Impairment	-850	0	0	0	-850	0	0
Divestiture					-239.8
Goodwill, end of period	2,981.50				2,981.50	4,057.70	4,057.80
Number of reporting units					3
Security [Member]
Goodwill [Roll Forward]
Impairment	($850)				($850)

Goodwill_and_Purchased_Intangi3

Goodwill and Purchased Intangible Assets, Finite Lived Intangible Assets by Class (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Purchased Intangible Assets [Line Items]
Net	$62.40
Total purchased intangible assets, gross	646.9	655.7
Total purchased intangible assets, accumulated amortization	-531.8	-516.1
Accumulated intangible asset impairment and other charges	-52.7	-32.7
Total purchased intangible assets, net	62.4	106.9
Amortization of intangible assets	36.3	31.9	32.3
Intangible assets no longer utilized	20		10.7
Impairment of intangible assets		0	5.4
Cost of revenues [Member]
Purchased Intangible Assets [Line Items]
Amortization of intangible assets	30.9	27.3	27.6
Impairment of intangible assets			16.1
Selling and marketing [Member]
Purchased Intangible Assets [Line Items]
Amortization of intangible assets	4.2	3.4	3.5
General and administrative [Member]
Purchased Intangible Assets [Line Items]
Amortization of intangible assets	1.2	1.2	1.2
Operating expenses [Member]
Purchased Intangible Assets [Line Items]
Amortization of intangible assets	5.4	4.6	4.7
Technologies and patents [Member]
Purchased Intangible Assets [Line Items]
Gross	567.7	581.4
Accumulated amortization	-466.1	-453.4
Impairment and other charges	-49.9	-30.5
Net	51.7	97.5
Customer Contracts, Support Agreements, and Related Relationships [Member]
Purchased Intangible Assets [Line Items]
Gross	78.1	74.3
Accumulated amortization	-65.2	-62.7
Impairment and other charges	-2.8	-2.2
Net	10.1	9.4
Other [Member]
Purchased Intangible Assets [Line Items]
Gross	1.1
Accumulated amortization	-0.5
Impairment and other charges	0
Net	0.6
Intangible Asset Write-Down [Member] | Restructuring Plan 2014 [Member] | Cost of revenues [Member]
Purchased Intangible Assets [Line Items]
Impairment of intangible assets	19.3
Intangible Asset Write-Down [Member] | Restructuring Plan 2014 [Member] | Restructuring and Other Charges [Member]
Purchased Intangible Assets [Line Items]
Impairment of intangible assets	$0.70

Goodwill_and_Purchased_Intangi4

Goodwill and Purchased Intangible Assets, Estimated Future Amortization Expense Intangible Assets (Details) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2015	$24.20
2016	13.8
2017	8.9
2018	5.2
2019	4.9
Thereafter	5.4
Net	$62.40

Other_Financial_Information_In

Other Financial Information, Inventories (Details) (USD $)	12 Months Ended			3 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2013	Jun. 30, 2014
Schedule of Inventory [Line Items]
Production materials	$38.30		$51.30
Finished goods	24.2		1.4
Total inventories, net	62.5		52.7
Restructuring charges, inventory write-down	69.3
Inventory Write-down		44.3
Restructuring Plan 2012 [Member]
Schedule of Inventory [Line Items]
Restructuring charges, inventory write-down	0.2	36.3
Inventory Write-down [Member]
Schedule of Inventory [Line Items]
Restructuring charges, inventory write-down			0
Inventory Write-down [Member] | Restructuring Plan 2014 [Member]
Schedule of Inventory [Line Items]
Restructuring charges, inventory write-down	$15.50			$11.50

Other_Financial_Information_Pr

Other Financial Information, Property and Equipment (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property and Equipment [Line Items]
Property and equipment, gross	$1,730.20	$1,709.10
Construction-in-process, gross	70.3	79.5
Accumulated depreciation	-825.9	-826.8
Property and equipment, net	904.3	882.3
Depreciation expense	141.9	148.2	154.7
Computers and equipment [Member]
Property and Equipment [Line Items]
Property and equipment, gross	806.1	794.6
Software [Member]
Property and Equipment [Line Items]
Property and equipment, gross	161.2	108.4
Leasehold improvements [Member]
Property and Equipment [Line Items]
Property and equipment, gross	179.5	202.6
Furniture and fixtures [Member]
Property and Equipment [Line Items]
Property and equipment, gross	33.7	42.5
Building and building Improvements [Member]
Property and Equipment [Line Items]
Property and equipment, gross	238.4	242.6
Land and land improvements [Member]
Property and Equipment [Line Items]
Property and equipment, gross	$241	$238.90

Other_Financial_Information_Ot

Other Financial Information, Other Long-Term Assets (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Other Financial Information [Abstract]
Privately-held investments	$89.90	$57.20
Licensed software	8.6	90.4
Federal income tax receivable	20	20
Customer financing receivable	16.9	19.9
Inventory	8	15.2
Prepaid costs, deposits, and other	35.5	31.1
Promissory note in connection with the sale of Junos Pulse	125	0
Other long-term assets	303.9	233.8
Restructuring Cost and Reserve [Line Items]
Restructuring charges	69.3
Impairment charges related to licensed software [Member] | Restructuring Plan 2014 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$85.40

Other_Financial_Information_Wa

Other Financial Information, Warranties (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Warranty Reserve [Roll Forward]
Beginning balance	$28	$29.70
Provisions made during the period, net	28.6	28.8
Adjustments related to pre-existing warranties	0	-2.1
Actual costs incurred during the period	-27.9	-28.4
Ending balance	$28.70	$28

Other_Financial_Information_De

Other Financial Information, Deferred Revenue (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Deferred Revenue [Abstract]
Deferred revenue, net	$1,075.70	$1,069.30
Deferred Revenue Reported as [Abstract]
Deferred revenue, current	780.8	705.8
Deferred revenue, long-term	294.9	363.5
Deferred product revenue [Member]
Deferred Revenue [Abstract]
Undelivered product commitments and other product deferrals	180.3	184.9
Distributor inventory and other sell-through items	103.7	118.7
Deferred gross product revenue	284	303.6
Deferred cost of product revenue	-58.4	-58.6
Deferred revenue, net	225.6	245
Deferred service revenue [Member]
Deferred Revenue [Abstract]
Deferred revenue, net	$850.10	$824.30

Other_Financial_Information_Ot1

Other Financial Information, Other Income (Expense), Net (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 01, 2014
Other Financial Information [Abstract]
Interest income									$10	$8.70	$11
Interest expense									-66.9	-58.4	-52.9
Net gain on legal settlement		0.8	195.3						196.1	0	0
Gain on investments									167.9	11.3	26.7
Gain on sale of Junos Pulse									19.6	0	0
Other									6.7	-2	-1.4
Other income (expense), net	7.4	-6.8	178.6	154.2	-10.2	-7.5	-12.6	-10.1	333.4	-40.4	-16.6
Interest expense, long-term debt									57.5	45.2	40
Capitalized interest									2.7	1.9	7.1
Publicly-traded equity and privately-held investments, net realized gain				163					163
Cost-method investments, realized gains (loss)										7.1
Significant Acquisitions and Disposals [Line Items]
Promissory note in connection with the sale of Junos Pulse	125				0				125	0
Junos Pulse [Member]
Significant Acquisitions and Disposals [Line Items]
Consideration												230.7
Cash consideration												105.7
Working capital adjustment												19.3
Promissory note in connection with the sale of Junos Pulse												$125

Restructuring_and_Other_Charge2

Restructuring and Other Charges (Details) (USD $)	3 Months Ended	12 Months Ended			3 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014
	sqft
	right
Restructuring Reserve [Line Items]
Restructuring and other charges		$208.50	$47.50	$99.70
Restructuring charges		69.3
Area subject to Restructuring Activities	400,000
Area subject to Sublease	100,000
Duration of sublease	2 years
Renewal Rights	1
Duration of renewal period	6 months
Deferred rent liability adjustment		9.8
Restructuring Reserve [Roll Forward]
31-Dec-13		17.8					17.8
Restructuring charges		69.3
Cash Payments		-75.9
Non-cash Settlements and Other		5.8
31-Dec-14		17	17.8		17
Restructuring Plan 2013 [Member]
Restructuring Reserve [Line Items]
Restructuring cost incurred to date		28.9			28.9
Restructuring Plan 2012 [Member]
Restructuring Reserve [Line Items]
Restructuring charges		0.2		36.3
Restructuring cost incurred to date		112.8			112.8
Restructuring Reserve [Roll Forward]
Restructuring charges		0.2		36.3
Cost of revenues [Member]
Restructuring Reserve [Line Items]
Restructuring and other charges		41.5	8.4	52.9
Cost of revenues [Member] | Restructuring Plan 2013 [Member]
Restructuring Reserve [Line Items]
Restructuring cost incurred to date		3.3			3.3
Cost of revenues [Member] | Restructuring Plan 2012 [Member]
Restructuring Reserve [Line Items]
Restructuring cost incurred to date		58			58
Restructuring and other charges [Member]
Restructuring Reserve [Line Items]
Restructuring and other charges		167	39.1	46.8
Restructuring and other charges [Member] | Restructuring Plan 2013 [Member]
Restructuring Reserve [Line Items]
Restructuring cost incurred to date		25.6			25.6
Restructuring and other charges [Member] | Restructuring Plan 2012 [Member]
Restructuring Reserve [Line Items]
Restructuring cost incurred to date		54.8			54.8
Severance [Member]
Restructuring Reserve [Line Items]
Restructuring and other charges		52.6	22.9	36.7
Restructuring charges		52.6
Restructuring Reserve [Roll Forward]
31-Dec-13		5.6					5.6
Restructuring charges		52.6
Cash Payments		-47.4
Non-cash Settlements and Other		-1.4
31-Dec-14		9.4	5.6		9.4
Severance [Member] | Restructuring Plan 2014 [Member]
Restructuring Reserve [Line Items]
Restructuring charges	7.1	52			6.9	9.9	28
Restructuring Reserve [Roll Forward]
Restructuring charges	7.1	52			6.9	9.9	28
Severance [Member] | Restructuring Plan 2013 [Member]
Restructuring Reserve [Line Items]
Restructuring cost incurred to date		0.6			0.6
Facilities [Member]
Restructuring Reserve [Line Items]
Restructuring and other charges		14.4	10	5.8
Restructuring charges		14.4
Restructuring Reserve [Roll Forward]
31-Dec-13		5.1					5.1
Restructuring charges		14.4
Cash Payments		-20.2
Non-cash Settlements and Other		8.1
31-Dec-14		7.4	5.1		7.4
Facilities [Member] | Restructuring Plan 2014 [Member]
Restructuring Reserve [Line Items]
Restructuring charges	25	14.2			1.6	37.6
Amount paid to Landlord	12.3
Transaction Fees	5.3
Restructuring Reserve [Roll Forward]
Restructuring charges	25	14.2			1.6	37.6
Contract termination and other [Member]
Restructuring Reserve [Line Items]
Restructuring and other charges		2.3	14.6	57.2
Restructuring charges		2.3
Restructuring Reserve [Roll Forward]
31-Dec-13		7.1					7.1
Restructuring charges		2.3
Cash Payments		-8.3
Non-cash Settlements and Other		-0.9
31-Dec-14		0.2	7.1		0.2
Contract termination and other [Member] | Restructuring Plan 2014 [Member]
Restructuring Reserve [Line Items]
Restructuring charges		2.3				1.5	0.8
Restructuring Reserve [Roll Forward]
Restructuring charges		2.3				1.5	0.8
Asset impairments and write-down [Member]
Restructuring Reserve [Line Items]
Restructuring and other charges		139.2	0	0
Asset impairments and write-down [Member] | Restructuring Plan 2014 [Member]
Restructuring Reserve [Line Items]
Restructuring charges	2.9	12.3			20.6	8.9	84.7
Restructuring Reserve [Roll Forward]
Restructuring charges	2.9	12.3			20.6	8.9	84.7
Impairment charges related to licensed software [Member] | Restructuring Plan 2014 [Member]
Restructuring Reserve [Line Items]
Restructuring charges		85.4
Restructuring Reserve [Roll Forward]
Restructuring charges		85.4
Inventory Write-down [Member]
Restructuring Reserve [Line Items]
Restructuring charges			0
Restructuring Reserve [Roll Forward]
Restructuring charges			0
Inventory Write-down [Member] | Restructuring Plan 2014 [Member]
Restructuring Reserve [Line Items]
Restructuring charges		15.5				11.5
Restructuring Reserve [Roll Forward]
Restructuring charges		15.5				11.5
Acceleration of Certain End of Life Products [Member] | Restructuring Plan 2014 [Member]
Restructuring Reserve [Line Items]
Restructuring charges		6.7				2.3	8.4
Restructuring Reserve [Roll Forward]
Restructuring charges		6.7				2.3	8.4
Employee Severance and Contract Terminations [Member]
Restructuring Reserve [Roll Forward]
31-Dec-14		$9.60			$9.60

LongTerm_Debt_and_Financing_De

Long-Term Debt and Financing (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 27, 2014	Mar. 31, 2011	Feb. 28, 2014
Long-Term Debt [Line Items]
Long-term debt	$1,350,000,000
Repurchase price percentage related to change in control	101.00%
Unaccreted Discount	-1,000,000
Long-term debt	1,349,000,000	999,300,000
Financing Arrangements [Abstract]
Sale of receivables	440,300,000	898,400,000	677,800,000
Proceeds from sale and collection of receivables	602,100,000	843,900,000	679,800,000
Receivables from sale of receivables	28,000,000	189,800,000
Maximum term for guarantees relating to third-party financing arrangements	4 years
Cash received from financing provider that has not been recognized as revenue	67,500,000	62,300,000
Fixed Rate Note Due 2016 [Member]
Long-Term Debt [Line Items]
Long-term debt	300,000,000				300,000,000
Effective interest rate	3.25%
Maturity date	15-Mar-16
Stated interest rate					3.10%
Fixed Rate Note Due 2021 [Member]
Long-Term Debt [Line Items]
Long-term debt	300,000,000				300,000,000
Effective interest rate	4.69%
Maturity date	15-Mar-21
Stated interest rate	4.60%
Fixed Rate Note Due 2024 [Member]
Long-Term Debt [Line Items]
Long-term debt	350,000,000					350,000,000
Effective interest rate	4.63%
Stated interest rate	4.50%					4.50%
Fixed Rate Note Due 2041 [Member]
Long-Term Debt [Line Items]
Long-term debt	400,000,000				400,000,000
Effective interest rate	6.03%
Maturity date	15-Mar-41
Stated interest rate	5.95%
Financing guarantee with recourse [Member]
Financing Arrangements [Abstract]
Guarantor obligations, current carrying value	22,200,000
Revolving Credit Facility [Member]
Long-Term Debt [Line Items]
Maximum borrowing capacity				500,000,000
Additional borrowing capacity				200,000,000
Federal Funds Rate [Member] | Revolving Credit Facility [Member]
Long-Term Debt [Line Items]
Basis spread on variable rate				0.50%
ICE Benchmark Administration Settlement Rate [Member] | Revolving Credit Facility [Member]
Long-Term Debt [Line Items]
Basis spread on variable rate				1.00%
Minimum [Member]
Financing Arrangements [Abstract]
Number of days due from receivable	30 days
Minimum [Member] | Base Rate [Member] | Revolving Credit Facility [Member]
Long-Term Debt [Line Items]
Basis spread on variable rate				0.00%
Minimum [Member] | Eurodollar [Member] | Revolving Credit Facility [Member]
Long-Term Debt [Line Items]
Basis spread on variable rate				0.90%
Maximum [Member]
Financing Arrangements [Abstract]
Number of days due from receivable	90 days
Maximum [Member] | Base Rate [Member] | Revolving Credit Facility [Member]
Long-Term Debt [Line Items]
Basis spread on variable rate				0.50%
Maximum [Member] | Eurodollar [Member] | Revolving Credit Facility [Member]
Long-Term Debt [Line Items]
Basis spread on variable rate				1.50%

Equity_Stock_Repurchase_Activi

Equity, Stock Repurchase Activities (Details) (USD $)	0 Months Ended	3 Months Ended				12 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Jul. 22, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 28, 2014	Oct. 31, 2014
						institution
						Dividend
Number of quarterly cash dividends declared						2
Cash dividends declared per common stock	$0.10	$0.10	$0.10	$0	$0	$0.20	$0	$0
Dividends paid						$86,000,000	$0	$0
Stock repurchase program, authorized amount									2,100,000,000
Repurchases under stock repurchase programs, shares repurchased						46.8	28.9	35.8
Repurchases under stock repurchase programs, average price per share (in dollar per share)						$22.42	$19.76	$18.05
Repurchases under stock repurchase programs, amount repurchased						1,050,000,000	570,600,000	645,600,000
Repurchases under accelerated share repurchase programs, shares repurchased						49.3
Repurchases under accelerated share repurchase programs, average price per share (in dollar per share)						$24.35
Repurchases for tax withholding, shares repurchased						0.6	0.4	0.2
Repurchases for tax withholding, average price per share (in dollar per share)						$19.69	$20.23	$23.40
Repurchases for tax withholding, amount repurchased						12,500,000	7,200,000	5,000,000
Number of accelerated share repurchase programs						2
Number of participating financial institutions in accelerated share repurchase programs						2
Accelerated Share Repurchases, Settlement (Payment) or Receipt		-1,200,000,000				-1,200,000,000
Intent, Stock Repurchases						1,000,000,000
Stock Repurchase Program 2014 [Member]
Stock repurchase program, authorized amount									1,200,000,000
Additional amount authorized under Stock Repurchase Plan										1,300,000,000
Stock repurchase program, remaining authorized repurchase amount		$1,200,000,000				$1,200,000,000

Equity_Accumulated_Other_Compr

Equity, Accumulated Other Comprehensive Income, Net of Tax (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Beginning Balance				$64.60				$4.70	$64.60	$4.70
Other comprehensive gain (loss) before reclassifications									30.4	62.4
Amount reclassified from accumulated other comprehensive income									-108.8	-2.5
Other comprehensive loss, net									-78.4	59.9	22.3
Ending Balance	-13.8				64.6				-13.8	64.6	4.7
Other expense	7.4	-6.8	178.6	154.2	-10.2	-7.5	-12.6	-10.1	333.4	-40.4	-16.6
Research and development expense	233.5	253.2	255.5	264	258.7	264.6	257.7	262.2	1,006.20	1,043.20	1,101.60
Selling and marketing expense	243	249.2	258	273.4	283.2	269.5	267.1	256.1	1,023.60	1,075.90	1,045.50
General and administrative expense	40.6	55	60.6	74.9	48.2	61.4	49.2	58.5	231.1	217.3	206.8
Cost of revenues	426.5	411.1	481.3	450	470	439.1	430.2	388.4	1,768.90	1,727.70	1,656.60
Unrealized Gains (Losses) on Available-for- Sale Securities [Member]
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Beginning Balance				66.2				2.1	66.2	2.1
Other comprehensive gain (loss) before reclassifications									48.7	65.1
Amount reclassified from accumulated other comprehensive income									-106.5	-1
Other comprehensive loss, net									-57.8	64.1
Ending Balance	8.4				66.2				8.4	66.2
Other expense									104.3	1
Unrealized Gains (Losses) on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Beginning Balance				2.2				3	2.2	3
Other comprehensive gain (loss) before reclassifications									-4.1	0.7
Amount reclassified from accumulated other comprehensive income									-2.3	-1.5
Other comprehensive loss, net									-6.4	-0.8
Ending Balance	-4.2				2.2				-4.2	2.2
Research and development expense									1.4	3.4
Selling and marketing expense									0.3	4.3
General and administrative expense									0.7	0.5
Cost of revenues									0.1	1.1
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income, Net of Tax [Roll Forward]
Beginning Balance				-3.8				-0.4	-3.8	-0.4
Other comprehensive gain (loss) before reclassifications									-14.2	-3.4
Amount reclassified from accumulated other comprehensive income									0	0
Other comprehensive loss, net									-14.2	-3.4
Ending Balance	($18)				($3.80)				($18)	($3.80)

Employee_Benefit_Plans_Details

Employee Benefit Plans (Details) (USD $)	12 Months Ended				36 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2014
Share-Based Compensation Plans
Options Assumed, Number of Shares			900,000
Common shares outstanding from equtiy awards through acquisition	4,100,000				4,100,000
Common stock - issued	416,200,000	495,200,000			416,200,000
Stock Option Activities
Beginning Balance, Number of Shares	23,100,000	34,100,000	38,600,000		38,600,000
Options Granted, Number of Shares			3,100,000
Options Assumed, Number of Shares			900,000
Options Canceled, Number of Shares	-600,000	-1,300,000	-2,800,000
Options Exercised, Number of Shares	-5,400,000	-5,600,000	-3,600,000
Options Expired, Number of Shares	-7,200,000	-4,100,000	-2,100,000
Ending Balance, Number of Shares	9,900,000	23,100,000	34,100,000	38,600,000	9,900,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Beginning Balance, Weighted Average Exercise Price	$25.15	$24.13	$23.98		23.98
Options Granted, Weighted Average Exercise Price			$22.81
Options Assumed, Weighted Average Exercise Price			$0.57
Options Canceled, Weighted Average Exercise Price	$30.15	$29.56	$26.64
Options Exercised, Weighted Average Exercise Price	$19.76	$15.58	$11.71
Options Expired, Weighted Average Exercise Price	$29.11	$28.35	$26.97
Ending Balance, Weighted Average Exercise Price	$24.87	$25.15	$24.13	$23.98	24.87
Weighted Average Remaining Contractual Term at Period End	2 years	2 years 4 months 24 days	3 years 1 month 6 days	3 years 8 months 12 days
Aggregate Intrinsic Value at Period End	$24,700,000	$44,600,000	$52,500,000	$75,300,000	24,700,000
Vested or Expected-to-Vest Options, Number of Shares at Period End	9,800,000				9,800,000
Vested or Expected-to-Vest Options, Weighted Average Exercise Price at Period End	$25				25
Vested and Expected-to-Vest Options, Weighted Average Remaining Contractual Term at Period End	2 years
Vested or Expected-to-Vest Options, Aggregate Intrinsic Value at Period End	23,600,000				23,600,000
Exercisable Options, Number of Shares at Period End	9,100,000				9,100,000
Exercisable Options, Weighted Average Exercise Price at Period End	$25.88				25.88
Exercisable Options, Weighted Average Remaining Contractual Term at Period End	1 year 8 months 12 days
Exercisable Options, Aggregate Intrinsic Value at Period End	15,900,000				15,900,000
Share Price	$22.32				22.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	33,400,000	29,400,000	27,900,000
Total Fair Value of Options Vested	20,800,000	45,200,000	70,900,000
Equity Incentive Plan 2006 [Member]
Share-Based Compensation Plans
Number of shares in authorized	149,500,000				149,500,000
Number of Shares Available for Future Issuance	47,800,000	49,100,000			47,800,000
Stock Option Activities
Options Canceled, Number of Shares	-600,000
Options Expired, Number of Shares	-7,200,000
Plan 1996 and 2000 [Member]
Share-Based Compensation Plans
Maximum Additional Shares Expire Unexercised, Under 1996 and 2000 Plan	75,000,000				75,000,000
Equity Incentive Plan 1996, 2000, and 2006 [Member]
Share-Based Compensation Plans
Shares outstanding under 2006 plan	27,100,000				27,100,000
Employee Stock Purchase Plan 2008 [Member]
Share-Based Compensation Plans
Common stock reserved for future issuance for equity incentive plans	19,000,000				19,000,000
Number of Shares Available for Future Issuance	3,300,000				3,300,000
Maximum Term for Options	1 year
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price	15.00%
Periodic Payroll Deduction - Percentage of Base Salary	10.00%				10.00%
Maximum Purchase of Common Stock, Shares	6,000
Share-based Compensation Arrangement by Share-based Payment Award, Offering Period	12 months
Maximum Purchase of Common Stock, Value	$25,000
Common stock - issued	15,700,000				15,700,000
Stock Compensation Plan [Member]
Share-Based Compensation Plans
Common stock reserved for future issuance for equity incentive plans	82,300,000				82,300,000
Stock Options [Member] | Equity Incentive Plan 2006 [Member]
Share-Based Compensation Plans
Option Vest Period	4 years
RSUs and PSAs [Member] | Equity Incentive Plan 2006 [Member]
Share-Based Compensation Plans
Vest period for share based compensation that vests solely based on continued employment	3 years
Vest period for share based compensation that vests based on other factors	1 year
From 2006 [Member] | Stock Options [Member] | Equity Incentive Plan 2006 [Member]
Share-Based Compensation Plans
Maximum Term for Options	7 years
Prior to 2006 [Member] | Stock Options [Member] | Prior to 2006 [Member]
Share-Based Compensation Plans
Maximum Term for Options	10 years
Mykonos, Contrail and WANDL [Member]
Share-Based Compensation Plans
Options Assumed, Number of Shares					8,500,000
Stock Option Activities
Options Assumed, Number of Shares					8,500,000

Employee_Benefit_Plans_Options

Employee Benefit Plans, Options Outstanding Exercise Price Range (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number Outstanding (in number of shares)	9.9
Weighted Average Remaining Contractual Life (in years)	2 years
Weighted Average Exercise (in dollars)	$24.87	$25.15	$24.13	$23.98
Number Exercisable (in number of shares)	9.1
Weighted Average Exercise Price (in dollars)	$25.88
$0.03 - $15.09
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$0.03
Exercise Price Range, Upper Range Limit	$15.09
Number Outstanding (in number of shares)	1.7
Weighted Average Remaining Contractual Life (in years)	3 years 7 months 6 days
Weighted Average Exercise (in dollars)	$9.58
Number Exercisable (in number of shares)	1.3
Weighted Average Exercise Price (in dollars)	$12.23
$16.39 - $22.59
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$16
Exercise Price Range, Upper Range Limit	$21.12
Number Outstanding (in number of shares)	1.4
Weighted Average Remaining Contractual Life (in years)	1 year 6 months
Weighted Average Exercise (in dollars)	$20.36
Number Exercisable (in number of shares)	1.2
Weighted Average Exercise Price (in dollars)	$20.34
$22.74 - $24.61
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$21.43
Exercise Price Range, Upper Range Limit	$23.84
Number Outstanding (in number of shares)	1.1
Weighted Average Remaining Contractual Life (in years)	2 years
Weighted Average Exercise (in dollars)	$23.85
Number Exercisable (in number of shares)	0.9
Weighted Average Exercise Price (in dollars)	$23.81
$24.73 - $24.73
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$23.89
Exercise Price Range, Upper Range Limit	$24.20
Number Outstanding (in number of shares)	0.1
Weighted Average Remaining Contractual Life (in years)	4 months 24 days
Weighted Average Exercise (in dollars)	$24.73
Number Exercisable (in number of shares)	0.1
Weighted Average Exercise Price (in dollars)	$24.73
$25.16- $25.16
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$24.25
Exercise Price Range, Upper Range Limit	$25.49
Number Outstanding (in number of shares)	1.2
Weighted Average Remaining Contractual Life (in years)	2 months 12 days
Weighted Average Exercise (in dollars)	$25.16
Number Exercisable (in number of shares)	1.2
Weighted Average Exercise Price (in dollars)	$25.16
$25.19 - $26.90
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$25.50
Exercise Price Range, Upper Range Limit	$26.90
Number Outstanding (in number of shares)	1
Weighted Average Remaining Contractual Life (in years)	1 year 3 months 18 days
Weighted Average Exercise (in dollars)	$26.24
Number Exercisable (in number of shares)	1
Weighted Average Exercise Price (in dollars)	$26.24
$26.97 - $29.89
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$26.97
Exercise Price Range, Upper Range Limit	$29.89
Number Outstanding (in number of shares)	1.6
Weighted Average Remaining Contractual Life (in years)	1 year 9 months 18 days
Weighted Average Exercise (in dollars)	$28.71
Number Exercisable (in number of shares)	1.6
Weighted Average Exercise Price (in dollars)	$28.70
$30.01 - $38.93
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$29.93
Exercise Price Range, Upper Range Limit	$38.93
Number Outstanding (in number of shares)	0.7
Weighted Average Remaining Contractual Life (in years)	2 years 10 months 24 days
Weighted Average Exercise (in dollars)	$33.57
Number Exercisable (in number of shares)	0.7
Weighted Average Exercise Price (in dollars)	$33.60
$40.26 - $40.26
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$40.26
Exercise Price Range, Upper Range Limit	$40.26
Number Outstanding (in number of shares)	0.7
Weighted Average Remaining Contractual Life (in years)	2 years 9 months 18 days
Weighted Average Exercise (in dollars)	$40.26
Number Exercisable (in number of shares)	0.7
Weighted Average Exercise Price (in dollars)	$40.26
$44.00 - $44.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$44
Exercise Price Range, Upper Range Limit	$44
Number Outstanding (in number of shares)	0.4
Weighted Average Remaining Contractual Life (in years)	3 years
Weighted Average Exercise (in dollars)	$44
Number Exercisable (in number of shares)	0.4
Weighted Average Exercise Price (in dollars)	$44

Employee_Benefit_Plans_Share_B

Employee Benefit Plans, Share Based Compensation, Equity Instruments Other Than Options (Details) (USD $)	0 Months Ended	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Feb. 20, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Awards Assumed, Weighted Average Grant-Date Fair Value				$22.21
Vested and Expected-to-Vest Options, Weighted Average Remaining Contractual Term at Period End		2 years
Fair value of RSUs, RSAs and PSAs		$210.10	$221.50	$132
Intended quarterly dividend	$0.10
Dividends paid, in dollar per share		$0.10
Dividends paid		86	0	0
Restricted Stock Units (RSUs) [Member]
Restricted Stock Units And Performance Share Awards Activities
Awards Granted, Number of Shares		10	10.3	9.9
Awards Assumed, Number of Shares		0.4		0.2
Awards Vested, Number of Shares		-7.3	-6.1	-3.1
Awards Canceled, Number of Shares		-4	-3.4	-2.9
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Awards Granted, Weighted Average Grant-Date Fair Value		$22.52	$20.32	$20.79
Awards Assumed, Weighted Average Grant-Date Fair Value		$22.66
Awards Vested, Weighted Average Grant-Date Fair Value		$22.98	$26.15	$27.04
Awards Canceled, Weighted Average Grant-Date Fair Value		$21.63	$22.99	$27.77
Restricted Stock Units (RSUs) [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		4 years
Performance Shares (PSAs) [Member]
Restricted Stock Units And Performance Share Awards Activities
Awards Granted, Number of Shares		1.4	2.2	2.2
Awards Assumed, Number of Shares		0.2
Awards Vested, Number of Shares		-1.1	-1.1	-1.9
Awards Canceled, Number of Shares		-3.2	-1.7	-2.3
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Awards Granted, Weighted Average Grant-Date Fair Value		$24.25	$21.27	$23.07
Awards Assumed, Weighted Average Grant-Date Fair Value		$22.66
Awards Vested, Weighted Average Grant-Date Fair Value		$36.19	$28.52	$18.21
Awards Canceled, Weighted Average Grant-Date Fair Value		$30.43	$29.10	$29.71
Aggregate Number Of Shares Subject to PSAs Granted		0.9	1.1	0.9
Minimum shares to be Issued on achievement of performance goals in respect of PSAs			0	0
Maximum shares to be issued on achievement of performance goals in respect of PSAs		1.4	2.2	2.2
Performance Shares (PSAs) [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		2 years
Performance Shares (PSAs) [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
RSUs, RSAs, and PSAs [Member]
Restricted Stock Units And Performance Share Awards Activities
Beginning Balance, Number of Shares		25.4	26.8	19.6
Ending Balance, Number of Shares		21.3	25.4	26.8	19.6
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Beginning Balance, Weighted Average Grant-Date Fair Value		$23.44	$27.76	$30.27
Ending Balance, Weighted Average Grant-Date Fair Value		$22.05	$23.44	$27.76	$30.27
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms		1 year 1 month 6 days	1 year 1 month 6 days	1 year 8 months 12 days	1 year 6 months
RSUs and PSAs, Aggregate Intrinsic Value at Period End		475	573.5	565	400.5
Vested and Expected-to-Vest RSUs and PSAs, Number of Shares at Period End		17.7
Vested and Expected-to-Vest RSUs and PSAs, Grant Date Fair Value		$21.99
Vested and Expected-to-Vest Options, Weighted Average Remaining Contractual Term at Period End		1 year
Vested and Expected-to-Vest RSUs and PSAs, Aggregate Intrinsic Value		$395.20
RSA [Member]
Restricted Stock Units And Performance Share Awards Activities
Awards Assumed, Number of Shares		0.9		5.8
Awards Vested, Number of Shares		-1.4	-1.6	-0.7
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Awards Assumed, Weighted Average Grant-Date Fair Value		$22.66		$19.59
Awards Vested, Weighted Average Grant-Date Fair Value		$19.59	$19.59	$19.59

Employee_Benefit_Plans_Shares_

Employee Benefit Plans, Shares Available For Grant (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Shares Available For Grant
Options Canceled, Number of Shares	600,000	1,300,000	2,800,000
Options Expired, Number of Shares	7,200,000	4,100,000	2,100,000
Shares counted against common shares authorized	2.1
Restricted Stock Units and Performance Share Awards [Member]
Shares Available For Grant
Fair Market Value on Date of Grant For RSUS And PSAS Issued at Discount, Maximum Percentage	100.00%
Equity Incentive Plan 2006 [Member]
Shares Available For Grant
Beginning Balance, Number of Shares	49,100,000
Awards Granted, Number of Shares	-24,100,000
Awards Canceled, Number of Shares	15,000,000
Options Canceled, Number of Shares	600,000
Options Expired, Number of Shares	7,200,000
Ending Balance, Number of Shares	47,800,000

Employee_Benefit_Plans_Assumpt

Employee Benefit Plans, Assumptions and Resulting Estimates of Fair Value (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Options [Member]
Estimates of Fair Value
Volatility			45.00%
Risk-free interest rate			0.70%
Expected life (years)			4 years 2 months 12 days
Dividend yield			0.00%
Weighted-average fair value per share			$8.47
Employee Stock Purchase Plan [Member]
Estimates of Fair Value
Volatility	30.00%	36.00%	47.00%
Risk-free interest rate	0.10%	0.10%	0.10%
Expected life (years)	6 months	6 months	6 months
Dividend yield		0.00%	0.00%
Weighted-average fair value per share	$5.72	$5.54	$5.53
Market-based RSUs [Member]
Estimates of Fair Value
Volatility	36.00%
Risk-free interest rate	1.60%
Weighted-average fair value per share	$16.89
Minimum [Member] | Stock Options [Member]
Estimates of Fair Value
Dividend yield	0.00%
Minimum [Member] | Market-based RSUs [Member]
Estimates of Fair Value
Dividend yield	0.00%
Maximum [Member] | Stock Options [Member]
Estimates of Fair Value
Dividend yield	1.80%
Maximum [Member] | Market-based RSUs [Member]
Estimates of Fair Value
Dividend yield	2.00%
Employee Stock Purchase Plan 2008 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Offering period (in months)	6 months
Common shares purchased through ESPP	2.9	3.3	3.5
Average exercise price of shares purchased through ESPP (in dollar per share)	$19.30	$16.53	$16.26

Employee_Benefit_Plans_Share_B1

Employee Benefit Plans, Share Based Compensation (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	$240	$244.60	$243.40
Stock Options [Member]
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	14.9	31.5	58.9
Unrecognized Compensation Cost	11.4
Weighted Average Period that Unrecognized Compensation Cost Will be Recognized (in years)	1 year 3 months 18 days
RSUs, RSAs, and PSAs [Member]
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	209.7	196.8	163.7
Employee Stock Purchase Plan [Member]
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	15.4	16.3	20.8
Restricted Stock Units and Performance Share Awards [Member]
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Unrecognized Compensation Cost	257.8
Weighted Average Period that Unrecognized Compensation Cost Will be Recognized (in years)	1 year 8 months 12 days
Cost of Revenues, Product [Member]
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	5	4.7	4.6
Cost of Revenues, Service [Member]
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	14.2	15.4	17
Research and Development Expense [Member]
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	134.5	127.6	109.1
Selling and Marketing Expense [Member]
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	60.2	70.9	81.6
General and Administrative Expense [Member]
Stock Based Compensation Expense Recorded in Cost and Expense Categories
Share-Based Compensation Expense	$26.10	$26	$31.10

Employee_Benefit_Plans_401k_pl

Employee Benefit Plans, 401(k) plan and Deferred Compensation Plan (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Benefit Textuals [Abstract]
Employee Contribution Matched in Percent	30.00%
Matching Contributions to Plan	$20.20	$20.70	$20.20
NQDC [Member]
Employee Benefit Textuals [Abstract]
Deferred Compensation Liability	$16.30	$15.40

Segments_Details

Segments (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Revenues [Abstract]
Net revenues	$1,101.60	$1,125.90	$1,229.50	$1,170.10	$1,273.60	$1,185.60	$1,150.70	$1,059.20	$4,627.10	$4,669.10	$4,365.40
Routing [Member]
Net Revenues [Abstract]
Net revenues									2,223.90	2,318	2,037.60
Switching [Member]
Net Revenues [Abstract]
Net revenues									721.2	638	554.8
Security [Member]
Net Revenues [Abstract]
Net revenues									463.6	563.9	669.7
Total product [Member]
Net Revenues [Abstract]
Net revenues									3,408.70	3,519.90	3,262.10
Total service [Member]
Net Revenues [Abstract]
Net revenues									$1,218.40	$1,149.20	$1,103.30

Segments_Geographical_Details

Segments, Geographical (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Revenues by Geographic Region [Line Items]
Total net revenues	$1,101.60	$1,125.90	$1,229.50	$1,170.10	$1,273.60	$1,185.60	$1,150.70	$1,059.20	$4,627.10	$4,669.10	$4,365.40
Property and equipment, net and purchased intangible assets, net	966.7				989.2				966.7	989.2
Verizon [Member] | Sales Revenue, Segment [Member] | Customer Concentration Risk [Member]
Net Revenues by Geographic Region [Line Items]
Concentration Risk, Percentage											10.30%
United States [Member]
Net Revenues by Geographic Region [Line Items]
Total net revenues									2,410.60	2,381.50	2,067.50
Property and equipment, net and purchased intangible assets, net	871.7				885.6				871.7	885.6
Other Americas [Member]
Net Revenues by Geographic Region [Line Items]
Total net revenues									219.7	232	218.4
Americas [Member]
Net Revenues by Geographic Region [Line Items]
Total net revenues									2,630.30	2,613.50	2,285.90
EMEA [Member]
Net Revenues by Geographic Region [Line Items]
Total net revenues									1,263.30	1,256.90	1,266.30
Asia Pacific [Member]
Net Revenues by Geographic Region [Line Items]
Total net revenues									733.5	798.7	813.2
International [Member]
Net Revenues by Geographic Region [Line Items]
Property and equipment, net and purchased intangible assets, net	$95				$103.60				$95	$103.60

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Components of income before provision for income taxes and noncontrolling interest
Domestic									($509.70)	$248.70	$114.10
Foreign									423.4	276.8	177.4
(Loss) income before income taxes	-694.4	165.6	294.5	148	185.2	137.5	125.9	76.9	-86.3	525.5	291.5
Current provision (benefit):
Federal									180.1	-12.9	94.3
States									15.2	-5	8.4
Foreign									33.7	32.5	37.1
Total current provision (benefit)									229	14.6	139.8
Deferred provision (benefit):
Federal									17.3	51.2	-28.8
States									1.2	-2.7	-1.5
Foreign									0.5	22.6	3.5
Total deferred provision (benefit)									19	71.1	-26.8
Income tax benefits attributable to employee stock plan activity									0	0	-8
Total provision for income taxes	75.2	62	73.4	37.4	33.4	38.4	28	-14.1	248	85.7	105
Income tax reconciliation
Expected provision at 35% rate									-30.2	184	102
State taxes (benefit), net of federal benefit									9.5	-3.6	2
Foreign income at different tax rates									-90.2	-37.7	-11.6
Research and development credits									-17.1	-32.5	-0.5
Share-based compensation									25.3	25.6	22.4
Non-deductible goodwill impairment									297.5	0	0
Gain on sale of Junos Pulse									75.6	0	0
Release of valuation allowance									-22.8	0	-3.4
Settlement with tax authorities									0	-28.3	0
Domestic production activities									-6.8	-26.3	0
Non-deductible compensation									3.2	1.5	0.6
Equity investment gain on acquisition									0	0	-5.3
Other									4	3	-1.2
Total provision for income taxes	75.2	62	73.4	37.4	33.4	38.4	28	-14.1	248	85.7	105
Net income tax benefit related to items unique during current year										64.2
Income tax benefit for a multi-year claim related to the U.S. production activities deduction										19.7
U.S. federal R&D tax credit resulting from the American Taxpayer Relief Act of 2012										$16.20

Income_Taxes_Deferred_Taxes_De

Income Taxes, Deferred Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets:
Net operating loss carry-forwards	$1,300,000	$1,100,000
Foreign tax credit carry-forwards	69,700,000	63,400,000
Research and other credit carry-forwards	122,500,000	106,600,000
Deferred revenue	104,900,000	71,000,000
Stock-based compensation	55,800,000	86,100,000
Reserves and accruals not currently deductible	129,800,000	153,900,000
Other	19,800,000	13,700,000
Total deferred tax assets	503,800,000	495,800,000
Valuation allowance	-144,500,000	-155,700,000
Deferred tax assets, net of valuation allowance	359,300,000	340,100,000
Deferred tax liabilities:
Property and equipment basis differences	-35,600,000	-3,100,000
Purchased intangibles	-16,700,000	-10,100,000
Unremitted foreign earnings	-260,600,000	-258,900,000
Deferred compensation and other	-5,100,000	-38,700,000
Other	0	-400,000
Total deferred tax liabilities	318,000,000	311,200,000
Current deferred tax assets	147,000,000	79,800,000
Long-term deferred tax assets	1,700,000	2,400,000
Long-term deferred tax liabilities	-107,400,000	-53,300,000
Net deferred tax assets	41,300,000	28,900,000
Valuation allowance	144,500,000	155,700,000
Change in DTA valuation allowance	11,200,000
Cumulative undistributed earnings of certain foreign subsidiaries	1,900,000,000
Federal [Member]
Deferred tax liabilities:
Net operating loss carry-forwards	1,600,000
California [Member]
Deferred tax liabilities:
Net operating loss carry-forwards	27,800,000
Tax credit carry-forwards	231,900,000
Tax credit carry-forward to be credited to APIC when realized	16,200,000
California Deferred Tax Assets [Member]
Deferred tax assets:
Valuation allowance	-125,200,000
Deferred tax liabilities:
Valuation allowance	125,200,000
Massachusetts Deferred Tax Assets [Member]
Deferred tax assets:
Valuation allowance	-9,700,000
Deferred tax liabilities:
Valuation allowance	9,700,000
Capital Loss Carryforward [Member]
Deferred tax assets:
Valuation allowance	-9,600,000
Deferred tax liabilities:
Valuation allowance	$9,600,000

Income_Taxes_Income_Tax_Contin

Income Taxes, Income Tax Contingencies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2009
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$137.60	$136.10	$132.20
Current Year [Abstract]
Additions	62.5	15.8	8.8
Prior Years [Abstract]
Additions	0.6	22.6	0.9
Reductions	0	-2.2	0
Settlements	0	-31.1	-1.2
Lapses in statutes of limitations	-1.5	-3.6	-4.6
Balance at end of year	199.2	137.6	136.1
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	164.9
Tax (expense) benefit recognized for net interest and penalties in the Consolidated Statements of Operations	-2.8	-0.6	0.6
Settlement including interest with the IRS related to intercompany R&D cost sharing arrangement		19.6
Maximum [Member]
Prior Years [Abstract]
Possible decrease in gross unrecognized tax benefits within next 12 months	-3.2
India Tax Authority [Member]
Prior Years [Abstract]
Penalties and interest accrued related to investigation of 2004 to 2008 tax return by India tax authorities				4.6
Other Long Term Liabilities [Member]
Prior Years [Abstract]
Interest and penalties accrued related to unrecognized tax benefits	$22.30	$18.40	$16.70

Net_Income_per_Share_Details

Net Income per Share (Details) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net (loss) income	($769.60)	$103.60	$221.10	$110.60	$151.80	$99.10	$97.90	$91	($334.30)	$439.80	$186.50
Denominator:
Weighted-average shares used to compute basic net income per share									457.4	501.8	520.9
Dilutive effect of employee stock awards									0	8.5	5.3
Weighted-average shares used to compute diluted net income per share									457.4	510.3	526.2
Net (loss) income per share attributable to Juniper Networks common stockholders:
Basic (in dollars per share)	($1.81)	$0.23	$0.47	$0.23	$0.30	$0.20	$0.19	$0.18	($0.73)	$0.88	$0.36
Diluted (in dollars per share)	($1.81)	$0.23	$0.46	$0.22	$0.30	$0.19	$0.19	$0.18	($0.73)	$0.86	$0.35
Net Income per Share Textuals
Anti-dilutive shares excluded from computation of diluted earnings per share									20.8	13.2	32.3

Commitments_and_Contingencies_2

Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2011	Feb. 28, 2014
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2015	$41,200,000
2016	30,100,000
2017	22,000,000
2018	14,300,000
2019	7,500,000
Thereafter	22,000,000
Total	137,100,000
Rent expense	46,000,000	52,800,000	63,200,000
Purchase commitments	476,200,000
Accrual for estimated carrying charges or obsolete materials charges	25,300,000
Senior notes	1,349,000,000	999,300,000
Long-term debt	1,350,000,000
Indemnity-related and service-related escrows	46,000,000
Campus build-out commitments	3,500,000
Non-cancelable agreements	19,200,000
Long-term income tax payable	177,500,000	114,400,000
Fixed Rate Note Due 2016 [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Long-term debt	300,000,000			300,000,000
Stated interest rate				3.10%
Fixed Rate Note Due 2021 [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Long-term debt	300,000,000			300,000,000
Stated interest rate	4.60%
Fixed Rate Note Due 2024 [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Long-term debt	350,000,000				350,000,000
Stated interest rate	4.50%				4.50%
Fixed Rate Note Due 2041 [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Long-term debt	400,000,000			400,000,000
Stated interest rate	5.95%
Purchase Commitment [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Net losses on firm purchase commitments	$9,400,000

Commitments_and_Contingencies_3

Commitments and Contingencies, Guarantees (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Financing guarantees, bank guarantees, and standby letters of credit [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, current carrying value	$26.20	$40.10
Financing guarantee with recourse [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, current carrying value	$22.20

Selected_Quarterly_Financial_D2

Selected Quarterly Financial Data (Unaudited) (Details) (USD $)	0 Months Ended	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jul. 22, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net revenues:
Product		$794	$809.50	$929.20	$876	$973.50	$900.80	$863.80	$781.80	$3,408.70	$3,519.90	$3,262.10
Service		307.6	316.4	300.3	294.1	300.1	284.8	286.9	277.4	1,218.40	1,149.20	1,103.30
Total net revenues		1,101.60	1,125.90	1,229.50	1,170.10	1,273.60	1,185.60	1,150.70	1,059.20	4,627.10	4,669.10	4,365.40
Cost of revenues:
Product		310.9	290	359.3	326.6	351.6	325.5	321.3	278.2	1,286.80	1,276.60	1,204
Service		115.6	121.1	122	123.4	118.4	113.6	108.9	110.2	482.1	451.1	452.6
Total cost of revenues		426.5	411.1	481.3	450	470	439.1	430.2	388.4	1,768.90	1,727.70	1,656.60
Gross margin		675.1	714.8	748.2	720.1	803.6	746.5	720.5	670.8	2,858.20	2,941.40	2,708.80
Operating expenses:
Research and development		233.5	253.2	255.5	264	258.7	264.6	257.7	262.2	1,006.20	1,043.20	1,101.60
Sales and marketing		243	249.2	258	273.4	283.2	269.5	267.1	256.1	1,023.60	1,075.90	1,045.50
General and administrative		40.6	55	60.6	74.9	48.2	61.4	49.2	58.5	231.1	217.3	206.8
Restructuring and other (credit) charges		9.8	-15	58.2	114	18.1	6	8	7
Impairment of goodwill		850	0	0	0					850	0	0
Total operating expenses		1,376.90	542.4	632.3	726.3	608.2	601.5	582	583.8	3,277.90	2,375.50	2,400.70
Operating (loss) income		-701.8	172.4	115.9	-6.2	195.4	145	138.5	87	-419.7	565.9	308.1
Other income (expense), net		7.4	-6.8	178.6	154.2	-10.2	-7.5	-12.6	-10.1	333.4	-40.4	-16.6
(Loss) income before income taxes		-694.4	165.6	294.5	148	185.2	137.5	125.9	76.9	-86.3	525.5	291.5
Income tax provision		75.2	62	73.4	37.4	33.4	38.4	28	-14.1	248	85.7	105
Net (loss) income		-769.6	103.6	221.1	110.6	151.8	99.1	97.9	91	-334.3	439.8	186.5
Net (loss) income per share:
Basic (in dollars per share)		($1.81)	$0.23	$0.47	$0.23	$0.30	$0.20	$0.19	$0.18	($0.73)	$0.88	$0.36
Diluted (in dollars per share)		($1.81)	$0.23	$0.46	$0.22	$0.30	$0.19	$0.19	$0.18	($0.73)	$0.86	$0.35
Cash dividends declared per common stock	$0.10	$0.10	$0.10	$0	$0					$0.20	$0	$0
Restructuring charges										69.3
Publicly-traded equity and privately-held investments, net realized gain					163					163
Net gain on legal settlement			0.8	195.3						196.1	0	0
Gain (loss) on disposition of business										19.6	0	0
Restructuring Plan 2013 [Member]
Operating expenses:
Restructuring and other (credit) charges						17.6
Operating expenses [Member] | Restructuring Plan 2013 [Member]
Operating expenses:
Restructuring and other (credit) charges							7.4
Cost of Sales [Member] | Restructuring Plan 2013 [Member]
Operating expenses:
Restructuring and other (credit) charges							3.7
Service Life [Member]
Net (loss) income per share:
Change in accounting estimate- depreciation expense impact						-7.9	-9.4	-11
Change in accounting estimate, diluted net income per share impact						$0.01	$0.01	$0.01
Junos Pulse [Member]
Net (loss) income per share:
Gain (loss) on disposition of business										19.6
Asset Write-Down [Member] | Restructuring Plan 2014 [Member]
Net (loss) income per share:
Restructuring charges		20.6	2.9	8.9	84.7					12.3
Employee Severance [Member]
Net (loss) income per share:
Restructuring charges										52.6
Employee Severance [Member] | Restructuring Plan 2014 [Member]
Net (loss) income per share:
Restructuring charges		6.9	7.1	9.9	28					52
Contract Termination [Member]
Net (loss) income per share:
Restructuring charges										2.3
Contract Termination [Member] | Restructuring Plan 2014 [Member]
Net (loss) income per share:
Restructuring charges				1.5	0.8					2.3
Acceleration of Certain End of Life Products [Member] | Restructuring Plan 2014 [Member]
Net (loss) income per share:
Restructuring charges				2.3	8.4					6.7
Facility Closing [Member]
Net (loss) income per share:
Restructuring charges										14.4
Facility Closing [Member] | Restructuring Plan 2014 [Member]
Net (loss) income per share:
Restructuring charges		1.6	25	37.6						14.2
Inventory Write-down [Member]
Net (loss) income per share:
Restructuring charges											0
Inventory Write-down [Member] | Restructuring Plan 2014 [Member]
Net (loss) income per share:
Restructuring charges				11.5						15.5
Security [Member]
Net revenues:
Total net revenues										463.6	563.9	669.7
Operating expenses:
Impairment of goodwill		$850								$850

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	0 Months Ended	3 Months Ended				12 Months Ended			0 Months Ended	2 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Jul. 22, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 27, 2015	Feb. 20, 2015
Subsequent Event [Line Items]
Cash dividends declared per common stock	$0.10	$0.10	$0.10	$0	$0	$0.20	$0	$0
Common Stock Repurchased Under Stock Repurchase Program Average Purchase Price						$22.42	$19.76	$18.05
First Quarter of 2015 [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Cash dividends declared per common stock									$0.10
Stock Repurchase Program 2014 [Member]
Subsequent Event [Line Items]
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$1,200,000,000				$1,200,000,000
Stock Repurchase Program 2014 [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Stock Repurchased During Period, Shares										10.9
Stock Repurchased During Period, Value										248,100,000
Common Stock Repurchased Under Stock Repurchase Program Average Purchase Price										$22.75
Stock Repurchase Program, Remaining Authorized Repurchase Amount										$926,900,000

Schedule_II_Valuation_and_Qual1

Schedule II- Valuation and Qualifying Account (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the beginning of year	$5.40	$9.50	$9.50
Charged to (Reversed from) Costs and Expenses	-0.7	-3.8	0.1
Write-offs, Net of Recoveries	0	-0.3	-0.1
Balance at the end of year	4.7	5.4	9.5
Sales Returns Reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the beginning of year	49	52.7	52
Charged as a Reduction in Revenues	53.2	35	40
Charged to Other Accounts	80.9	61.5	48.6
Used	-132.9	-100.2	-87.9
Balance at the end of year	$50.20	$49	$52.70