Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2015
Summary of Significant Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The Company prepares its consolidated financial statements in conformity with accounting principles generally accepted in the United States of America. These principles require management to make estimates, judgments and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and the amounts disclosed in the related notes to the consolidated financial statements. Actual results and outcomes may differ materially from management’s estimates, judgments and assumptions. Significant estimates, judgments and assumptions used in these financial statements include, but are not limited to, those related to revenue, accounts receivable and related reserves, valuation and impairment of investments and marketable securities, useful lives and realizability of long-lived assets, capitalized internal-use software development costs, income tax reserves and accounting for stock-based compensation. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. The effects of material revisions in estimates are reflected in the consolidated financial statements prospectively from the date of the change in estimate.
Cash, Cash Equivalents and Marketable Securities	Cash, Cash Equivalents and Marketable Securities Cash and cash equivalents consist of cash held in bank deposit accounts and short-term, highly-liquid investments with remaining maturities of three months or less at the date of purchase. Marketable securities consist of corporate, government and other securities. Securities having remaining maturities of more than three months at the date of purchase and less than one year from the date of the balance sheet are classified as short-term, and those with maturities of more than one year from the date of the balance sheet are classified as long-term in the consolidated balance sheet. The Company classifies its debt and equity investments with readily determinable market values as available-for-sale. These investments are classified as marketable securities on the consolidated balance sheets and are carried at fair market value, with unrealized gains and losses considered to be temporary in nature and reported as accumulated other comprehensive loss, a separate component of stockholders’ equity. The Company reviews all investments for reductions in fair value that are other-than-temporary. When such reductions occur, the cost of the investment is adjusted to fair value through recording a loss on investments in the consolidated statements of income. Gains and losses on investments are calculated on the basis of specific identification. Marketable securities are considered to be impaired when a decline in fair value below cost basis is determined to be other-than-temporary. The Company periodically evaluates whether a decline in fair value below cost basis is other-than-temporary by considering available evidence regarding these investments including, among other factors: the duration of the period that, and extent to which, the fair value is less than cost basis; the financial health and business outlook of the issuer, including industry and sector performance and operational and financing cash flow factors; overall market conditions and trends and the Company’s intent and ability to retain its investment in the security for a period of time sufficient to allow for an anticipated recovery in market value. Once a decline in fair value is determined to be other-than-temporary, a write-down is recorded and a new cost basis in the security is established. Assessing the above factors involves inherent uncertainty. Write-downs, if recorded, could be materially different from the actual market performance of marketable securities in the Company’s portfolio if, among other things, relevant information related to the marketable securities was not publicly available or other factors not considered by the Company would have been relevant to the determination of impairment.
Accounts Receivable and Related Reserves	Accounts Receivable and Related Reserves The Company’s accounts receivable balance includes unbilled amounts that represent revenue recorded for customers that are typically billed monthly in arrears. The Company records reserves against its accounts receivable balance. These reserves consist of allowances for doubtful accounts and reserves for cash-basis customers. Increases and decreases in the allowance for doubtful accounts are included as a component of general and administrative expense in the consolidated statements of income. The Company’s reserve for cash-basis customers increases as services are provided to customers where collection is no longer assured. Increases to the reserve for cash-basis customers are recorded as reductions of revenue. The reserve decreases and revenue is recognized when and if cash payments are received. Estimates are used in determining these reserves and are based upon the Company’s review of outstanding balances on a customer-specific, account-by-account basis. The allowance for doubtful accounts is based upon a review of customer receivables from prior sales with collection issues where the Company no longer believes that the customer has the ability to pay for services previously provided. The Company also performs ongoing credit evaluations of its customers. If such an evaluation indicates that payment is no longer reasonably assured for services provided, any future services provided to that customer will result in the creation of a cash-basis reserve until the Company receives consistent payments. The Company does not have any off-balance sheet credit exposure related to its customers.
Concentrations of Credit Risk	Concentrations of Credit Risk The amounts reflected in the consolidated balance sheets for accounts receivable, other current assets, accounts payable, accrued liabilities and other current liabilities approximate their fair values due to their short-term maturities. The Company maintains the majority of its cash, cash equivalents and marketable securities with major financial institutions that the Company believes to be of high credit standing. The Company believes that, as of December 31, 2015, its concentration of credit risk related to cash equivalents and marketable securities was not significant. Concentrations of credit risk with respect to accounts receivable are primarily limited to certain customers to which the Company makes substantial sales. The Company’s customer base consists of a large number of geographically-dispersed customers diversified across several industries. To reduce risk, the Company routinely assesses the financial strength of its customers. Based on such assessments, the Company believes that its accounts receivable credit risk exposure is limited. For the years ended December 31, 2015, 2014 and 2013, no customer accounted for more than 10% of total revenue. As of December 31, 2015 and 2014, no customers had an accounts receivable balance greater than 10% of total accounts receivable. The Company believes that, as of December 31, 2015, its concentration of credit risk related to accounts receivable was not significant.
Fair Value of Financial Measurements	Fair Value of Financial Measurements Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The Company has certain financial assets and liabilities recorded at fair value, principally cash equivalents and short- and long-term marketable securities, that have been classified as Level 1, 2 or 3 within the fair value hierarchy. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company can access at the reporting date. Fair values determined by Level 2 inputs utilize data points other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Fair values determined by Level 3 inputs are based on unobservable data points for the asset or liability.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost, net of accumulated depreciation and amortization. Property and equipment generally include purchases of items with a per-unit value greater than $1,000 and an estimated useful life greater than one year. Depreciation and amortization are computed on a straight-line basis over the estimated useful lives of the assets. Leasehold improvements are amortized over the shorter of the related lease terms or their estimated useful lives. The Company periodically reviews the estimated useful lives of property and equipment and any changes to the estimated useful lives are recorded prospectively from the date of the change. Upon retirement or sale, the cost of the assets disposed of and the related accumulated depreciation are removed from the accounts, and any resulting gain or loss is included in income from operations. Repairs and maintenance costs are expensed as incurred.
Goodwill, Acquired Intangible Assets and Long-Lived Assets	Goodwill, Acquired Intangible Assets and Long-Lived Assets Goodwill is the amount by which the cost of acquired net assets in a business combination exceeds the fair value of the net identifiable assets on the date of purchase and is carried at its historical cost. The Company tests goodwill for impairment on an annual basis or more frequently if events or changes in circumstances indicate that the asset might be impaired. The Company performs its impairment test of goodwill as of December 31. As of December 31, 2015, 2014 and 2013, the fair value of the Company's reporting unit was substantially in excess of the carrying value. The tests did not result in an impairment to goodwill during the years ended December 31, 2015, 2014 and 2013. Acquired intangible assets consist of completed technologies, customer relationships, trademarks and trade names, non-compete agreements and acquired license rights. Acquired intangible assets, other than goodwill, are amortized over their estimated useful lives based upon the estimated economic value derived from the related intangible asset. Long-lived assets, including property and equipment and acquired intangible assets, are reviewed for impairment whenever events or changes in circumstances, such as service discontinuance, technological obsolescence, significant decreases in the Company’s market capitalization, facility closures or work-force reductions indicate that the carrying amount of the long-lived asset may not be recoverable. When such events occur, the Company compares the carrying amount of the asset to the undiscounted expected future cash flows related to the asset. If this comparison indicates that an impairment is present, the amount of the impairment is calculated as the difference between the carrying amount and the fair value of the asset. The Company did not have any impairments during the years ended December 31, 2015, 2014 and 2013.
Revenue Recognition	Revenue Recognition The Company recognizes service revenue in accordance with the authoritative guidance for revenue recognition, including guidance on revenue arrangements with multiple deliverables. Revenue is recognized only when the price is fixed or determinable, persuasive evidence of an arrangement exists, the service is performed and collectability of the resulting receivable is reasonably assured. The Company primarily derives revenue from the sale of services to customers executing contracts having terms of one year or longer. These contracts generally commit the customer to a minimum of monthly, quarterly or annual level of usage and specify the rate at which the customer must pay for actual usage above the monthly, quarterly or annual minimum. For contracts with a monthly commitment, the Company recognizes the monthly minimum as revenue each month, provided that an enforceable contract has been signed by both parties, the service has been delivered to the customer, the fee for the service is fixed or determinable and collection is reasonably assured. Should a customer’s usage of the Company's services exceed the monthly, quarterly or annual minimum, the Company recognizes revenue for such excess in the period of additional usage. For annual or other non-monthly period revenue commitments, the Company recognizes revenue monthly based upon the customer’s actual usage each month of the commitment period and only recognizes any remaining committed amount for the applicable period in the last month thereof. The Company typically charges its customers an integration fee when the services are first activated. Integration fees are recorded as deferred revenue and recognized as revenue ratably over the estimated life of the customer arrangement. The Company also derives revenue from services sold as discrete, non-recurring events or based solely on usage. For these services, the Company recognizes revenue once the event or usage has occurred. When more than one element is contained in a revenue arrangement, the Company determines the fair value for each element in the arrangement based on vendor-specific objective evidence (“VSOE”) for each respective element, including any renewal rates for services contractually offered to the customer. Elements typically included in the Company's multiple element arrangements consist of its core services – the delivery of content, applications and software over the Internet – as well as mobile and security solutions, and enterprise professional services. These elements have value to the customer on a stand-alone basis in that they can be sold separately by another vendor. Generally, there is no right of return relative to these services. The Company typically uses VSOE to determine the fair value of its separate elements. All stand-alone sales of professional services are reviewed to establish the average stand-alone selling price for those services. For the Company's core services, the fair value is the price charged for a single deliverable on a per unit basis when it is sold separately. For arrangements in which the Company is unable to establish VSOE, third party evidence ("TPE") of the fair value of each element is determined based upon the price charged when the element is sold separately by another vendor. For arrangements in which the Company is unable to establish VSOE or TPE for each element, the Company uses the best estimate of selling price ("BESP") to determine the fair value of the separate deliverables. The Company estimates BESP based upon a management-approved listing of all solution unit pricing and pre-established discount levels for each solution that takes into consideration volume, geography and industry lines. The Company allocates arrangement consideration across the multiple elements using the relative selling price method. At the inception of a customer contract, the Company makes an assessment as to that customer’s ability to pay for the services provided. The Company bases its assessment on a combination of factors, including the successful completion of a credit check or financial review, its collection experience with the customer and other forms of payment assurance. Upon the completion of these steps, the Company recognizes revenue monthly in accordance with its revenue recognition policy. If the Company subsequently determines that collection from the customer is not reasonably assured, the Company records an allowance for doubtful accounts and bad debt expense for all of that customer’s unpaid invoices and ceases recognizing revenue for continued services provided until cash is received from the customer. Changes in the Company’s estimates and judgments about whether collection is reasonably assured would change the timing of revenue or amount of bad debt expense that the Company recognizes. The Company also sells its services through a reseller channel. Assuming all other revenue recognition criteria are met, the Company recognizes revenue from reseller arrangements based on the reseller’s contracted non-refundable minimum purchase commitments over the term of the contract, plus amounts sold by the reseller to its customers in excess of the minimum commitments. Amounts attributable to this excess usage are recognized as revenue in the period in which the service is provided. From time to time, the Company enters into contracts to sell its services or license its technology to unrelated enterprises at or about the same time that it enters into contracts to purchase products or services from the same enterprises. If the Company concludes that these contracts were negotiated concurrently, the Company records as revenue only the net cash received from the vendor, unless the product or service received has a separate identifiable benefit, and the fair value of the vendor’s product or service can be established objectively. The Company may from time to time resell licenses or services of third parties. The Company records revenue for these transactions on a gross basis when the Company has risk of loss related to the amounts purchased from the third party and the Company adds value to the license or service, such as by providing maintenance or support for such license or service. If these conditions are present, the Company recognizes revenue when all other revenue recognition criteria are satisfied. Deferred revenue represents amounts billed to customers for which revenue has not been recognized. Deferred revenue primarily consists of the unearned portion of monthly billed service fees, prepayments made by customers for future periods, deferred integration and activation set-up fees and amounts billed under customer arrangements with extended payment terms.
Cost of Revenues	Cost of Revenue Cost of revenue consists primarily of fees paid to network providers for bandwidth and to third party network data centers for housing servers, also known as co-location costs. Cost of revenue also includes employee costs for network operation, build-out and support and services delivery; network storage costs; cost of software licenses; depreciation of network equipment used to deliver the Company’s services; amortization of network-related internal-use software; and costs for the production of live events. The Company enters into contracts for bandwidth with third party network providers with terms typically ranging from several months to two years. These contracts generally commit the Company to pay minimum monthly fees plus additional fees for bandwidth usage above the committed level. In some circumstances, Internet service providers (“ISPs”) make rack space available for the Company’s servers and access to their bandwidth at a discount or no cost. In exchange, the ISP and its customers benefit by receiving content through a local Company server resulting in better content delivery. The Company does not consider these relationships to represent the culmination of an earnings process. Accordingly, the Company does not recognize as revenue the value to the ISPs associated with the use of the Company’s servers, nor does the Company recognize as expense the value of the rack space and bandwidth received at discounted or no cost.
Research and Development Costs and Capitalized Internal-Use Software	Research and Development Costs and Capitalized Internal-Use Software Research and development costs consist primarily of payroll and related personnel costs for the design, development, deployment, testing and enhancement of the Company’s services and network. Costs incurred in the development of the Company’s services are expensed as incurred, except certain internal-use software development costs eligible for capitalization. Capitalized costs include external consulting fees, payroll and payroll-related costs and stock-based compensation for employees in the Company’s development and information technology groups who are directly associated with, and who devote time to, the Company’s internal-use software projects. Capitalization begins when the planning stage is complete and the Company commits resources to the software project, and continues during the application development stage. Capitalization ceases when the software has been tested and is ready for its intended use. Costs incurred during the planning, training and post-implementation stages of the software development life-cycle are expensed as incurred. The Company amortizes completed internal-use software that is used on its network to cost of revenue over its estimated useful life.
Advertising Expense	Advertising Expense The Company recognizes advertising expense as incurred. The Company recognized total advertising expense of $3.6 million for the year ended December 31, 2015, and $2.7 million for each of the years ended December 31, 2014 and 2013.
Accounting for Stock-Based Compensation	Accounting for Stock-Based Compensation The Company recognizes compensation costs for all stock-based payment awards made to employees based upon the awards’ grant-date fair value. The stock-based payment awards include stock options, restricted stock units, deferred stock units and employee stock purchases related to the Company’s employee stock purchase plan. For stock options, the Company has selected the Black-Scholes option-pricing model to determine the fair value of stock option awards. For stock options, restricted stock units and deferred stock units that contain only a service-based vesting feature, the Company recognizes compensation cost on a straight-line basis over the award's vesting period. For awards with a performance condition-based vesting feature, the Company recognizes compensation cost on a graded-vesting basis over the award's expected vesting period, commencing when achievement of the performance condition is deemed probable. In addition, for awards that vest and become exercisable only upon achievement of specified performance conditions, the Company makes judgments and estimates each quarter about the probability that such performance conditions will be met or achieved. Any changes to those estimates that the Company makes from time to time may have a significant impact on the stock-based compensation expense recorded and could materially impact the Company’s results of operation.
Foreign Currency Translation and Forward Currency Contracts	Foreign Currency Translation and Forward Currency Contracts The assets and liabilities of the Company's subsidiaries are translated at the applicable exchange rate as of the balance sheet date, and revenue and expenses are translated at an average rate over the period. Resulting currency translation adjustments are recorded as a component of accumulated other comprehensive loss, a separate component of stockholders’ equity. Gains and losses on inter-company and other non-functional currency transactions are recorded in other expense, net. The Company enters into short-term foreign currency forward contracts to offset foreign exchange gains and losses generated by the re-measurement of certain assets and liabilities recorded in non-functional currencies. Changes in the fair value of these derivatives, as well as re-measurement gains and losses, are recognized in current earnings in other expense, net. As of December 31, 2015 and 2014, the fair value of the forward currency contracts and the underlying net gains for the years ended December 31, 2015, 2014 and 2013 were immaterial. The Company's foreign currency forward contracts may be exposed to credit risk to the extent that its counterparties are unable to meet the terms of the agreements. The Company seeks to minimize counterparty credit (or repayment) risk by entering into transactions only with major financial institutions of investment grade credit rating.
Taxes	Taxes The Company's provision for income taxes is comprised of a current and a deferred portion. The current income tax provision is calculated as the estimated taxes payable or refundable on tax returns for the current year. The deferred income tax provision is calculated as the estimated future tax effects attributable to temporary differences and carryforwards using expected tax rates in effect during the years in which the differences are expected to reverse or the carryforwards are expected to be realized. The Company currently has net deferred tax assets consisting of net operating loss (“NOL”) carryforwards, tax credit carryforwards and deductible temporary differences. Management periodically weighs the positive and negative evidence to determine if it is more likely than not that some or all of the deferred tax assets will be realized. The Company has recorded certain tax reserves to address potential exposures involving its income tax and sales and use tax positions. These potential tax liabilities result from the varying application of statutes, rules, regulations and interpretations by different taxing jurisdictions. The Company's estimate of the value of its tax reserves contains assumptions based on past experiences and judgments about the interpretation of statutes, rules and regulations by taxing jurisdictions. It is possible that the costs of the ultimate tax liability or benefit from these matters may be more or less than the amount the Company estimated. Uncertainty in income taxes is recognized in the Company's consolidated financial statements using a two-step process. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The Company has elected to account for the indirect income tax effects of stock-based compensation as provision for income taxes. This primarily includes the impact of the research and development tax credit and the domestic production activities deduction.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued updated guidance and disclosure requirements for recognizing revenue. The new revenue recognition standard provides a five-step analysis of transactions to determine when and how revenue is recognized. The core principle is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This standard will be effective for the Company on January 1, 2018, and may be applied retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. The Company is evaluating the potential impact of adopting this new accounting guidance. In April 2015, the FASB issued updated guidance that will change the current presentation of debt issuance costs on the balance sheet. This new guidance will move debt issuance costs from the assets section of the balance sheet to the liabilities section as a direct deduction from the carrying amount of the debt issued. The guidance will be effective for the Company on January 1, 2016. The Company will reclassify its debt issuance costs included in other assets on the consolidated balance sheet to convertible senior notes within the liabilities and stockholders' equity section. The amount of deferred financing costs expected to be reclassified as of January 1, 2016 is $6.2 million. This revision will have no impact on the Company's results of operations or cash flows. In September 2015, the FASB issued updated guidance that eliminates the requirement to restate prior period financial statements for measurement period adjustments. In an effort to reduce complexity in financial reporting, the new guidance requires that the cumulative impact of a measurement period adjustment, including the impact on prior periods, be recognized in the reporting period in which the adjustment is identified. The standard will be effective for the Company on January 1, 2016. The Company does not expect this guidance to have a material impact on its results of operations, financial condition or cash flows. In November 2015, the FASB issued guidance that requires companies to present deferred income tax assets and liabilities as noncurrent in a classified balance sheet instead of the current requirement to separate deferred income tax assets and liabilities into current and noncurrent amounts. The standard is effective for the Company on January 1, 2016, but early adoption is permitted. The Company has adopted this standard as of December 31, 2015, and has applied it prospectively. The Company early adopted the standard because it simplifies the Company's process of determining balance sheet classification for its deferred taxes. Prior period deferred income tax assets and liabilities have not been adjusted, due to the prospective application of the standard. The adoption of this standard did not have an impact on the Company's results of operations or financial condition.