Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2020
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, valuation and useful lives of acquired intangible assets, 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.
Newly-Adopted Accounting Pronouncements and Recent Accounting Pronouncements	Newly-Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standards Board ("FASB") issued guidance that introduces a new methodology for accounting for credit losses on financial instruments. The guidance establishes a new "expected credit loss model" that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Any expected credit losses are to be reflected as allowances. The Company prospectively adopted this standard on January 1, 2020. Adoption of the standard did not have a material impact on the Company's consolidated financial statements. In August 2018, the FASB issued guidance that addresses a customer’s accounting for implementation costs incurred in a cloud computing arrangement that is a service contract. The guidance aligns the accounting for costs incurred to implement a cloud computing arrangement that is a service arrangement with the guidance for capitalizing costs associated with developing or obtaining internal-use software. The Company prospectively adopted this standard on January 1, 2020. Adoption of the standard did not have a material impact on the Company's consolidated financial statements. Recent Accounting Pronouncements In August 2020, the FASB issued guidance that is expected to reduce complexity and improve comparability of financial reporting associated with accounting for convertible instruments and contracts in an entity’s own equity. This guidance will be effective for the Company on January 1, 2022. The Company is evaluating the potential impact of adopting this new accounting guidance on its consolidated financial statements related to the accounting for convertible debt arrangements.
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 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 sheets. The Company classifies its debt securities 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 which primarily consists of allowances for current expected credit losses. Increases and decreases in the allowance for current expected credit losses are included as a component of general and administrative expense in the consolidated statements of income. The allowance for current expected credit losses has been developed using historical loss rates for the previous twelve months as well as expectations about the future where the Company has been able to develop forecasts to support its estimates. In addition, the allowance considers outstanding balances on a customer-specific, account-by-account basis. The Company assesses collectibility 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.
Revenue Recognition, Incremental Costs to Obtain a Contract with a Customer, Contract Liabilities and Cost of Revenue	Incremental Costs to Obtain a Contract with a Customer The Company capitalizes incremental costs associated with obtaining customer contracts, specifically certain commission and incentive payments. The Company pays commissions and incentives up-front based on contract value upon signing a new arrangement with a customer and upon renewal and upgrades of existing contracts with customers if the renewal and upgrades result in an incremental increase in contract value. To the extent commissions and incentives are earned, the expenses, including estimated payroll taxes, are deferred on the Company's consolidated balance sheet and amortized over the expected life of the customer arrangement on a straight-line basis. Based on the nature of the Company's unique technology and services, and the rate at which the Company continually enhances and updates its technology, the expected life of the customer arrangement is determined to be approximately 2.5 years. Additionally, the Company may pay commissions and incentives based upon contract value, rather than incremental increase in contract value, to certain sales groups within the Company. For these commission arrangements, the Company amortizes capitalized costs for contract renewals over an average renewal contract period of 16 months. The Company also incurs commission expense on an ongoing basis based upon revenue recognized. In these cases, no incremental costs are deferred, as the commissions are earned and expensed in the same period for which the associated revenue is recognized. Amortization of the costs is primarily included in sales and marketing expense in the consolidated statements of income. The current portion of deferred commission and incentive payments is included in prepaid expenses and other current assets, and the long-term portion is included in other assets on the Company's consolidated balance sheets. Contract Liabilities Contract liabilities primarily represent payments received from customers for which the related performance obligations have not yet been satisfied. These balances consist of the unearned portion of monthly service fees and integration fees and prepayments made by customers for future periods. The current and long-term portions of the Company's contract liabilities are included in deferred revenue in the respective sections of the Company's consolidated balance sheets. Revenue Recognition The Company primarily derives revenue from the sale of services to customers executing contracts having terms of one year or longer. Services included in the Company's contracts consist of its core services – the delivery of content, applications and software over the internet – as well as security solutions and professional services. Revenue is recognized upon transfer of control of promised services in an amount that reflects the consideration the Company expects to receive in exchange for those services. The Company enters into contracts that may include various combinations of these services, which are generally capable of being distinct and accounted for as separate performance obligations. These contracts generally commit the customer to a minimum of monthly, quarterly or annual levels of usage and specify the rate at which the customer must pay for actual usage above the stated minimum. Based on the typical structure of the Company's contracts, which are generally for monthly recurring services that are essentially the same over time and have the same pattern of transfer to the customer, most performance obligations represent a promise to deliver a series of distinct services over time. The Company's contracts with customers sometimes include promises to deliver multiple services to a customer. Determining whether services are distinct performance obligations often requires the exercise of judgment by management. For example, advanced features that enhance a service and are highly interrelated are generally not considered distinct; rather, they are combined with the service they relate to into one performance obligation. Different determinations related to combining services into performance obligations could result in differences in the timing and amount of revenue recognized in a period. Generally, the transaction price in a contract is equal to the committed price stated in the contract, less any discounts or rebates. The Company's typical contracts qualify for series accounting, and the pricing terms generally do not require estimation of the transaction price beyond the reporting period. As a result, any incremental fees generated as a result of usage or “bursting” over committed contract levels are recorded in the period to which the services relate. The amount of consideration recognized for usage above contract minimums is limited to the amount the Company expects to be entitled to receive in exchange for providing the services. Once the transaction price has been determined, the Company allocates such price among all performance obligations in the contract on a relative standalone selling price (“SSP”) basis. Determination of SSP requires the exercise of judgment by management. SSP is based on observable inputs such as the price the Company charges for the service when sold separately or the discounted list price per management’s approved price list. In cases where services are not sold separately or price list rates are not available, a cost-plus-margin approach or adjusted market approach is used to determine SSP. Most content delivery and security services represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by the Company. Accordingly, revenue for those services is recognized over time, generally ratably over the term of the arrangement due to consistent monthly traffic commitments that expire each period. Any bursting over given commitments is recognized in the period in which the traffic was served. For services that involve traffic consumption, revenue is recognized in an amount that reflects the level of traffic served to a customer in a given period. For custom arrangements, other methods may be used as a measure of progress towards satisfying the performance obligations. Some of the Company's services are satisfied at a point in time, such as one-time professional services contracts, integration services and most license sales where the primary obligation is delivery of the license at the start of the term. In these cases, revenue is recognized at the point in time of delivery or satisfaction of the performance obligation. 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. Consideration payable to a customer is reviewed as part of the transaction price. If the payment to the customer does not represent payment for a distinct service, revenue is recognized only up to the net amount of consideration after customer payment obligations are considered. The Company may also resell the licenses or services of third parties. If the Company is acting as an agent in an arrangement with a customer to provide third party services, the transaction price reflects only the net amount to which the Company will be entitled, after accounting for payments made to the third party responsible for satisfying the performance obligation. 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 services delivery and network operation, build-out and support of the Company's network; 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 streamed by the Company for customers. The Company enters into contracts for bandwidth with third-party network providers with terms typically ranging from several months to five 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 to locate its servers and provide access to their bandwidth at a discount or no cost. Although the Company does not provide any goods or services to the ISPs or the ISPs’ customers under these arrangements, the ISPs and their customers indirectly benefit by accessing content through a local Company server, resulting in better content delivery. The Company records the cost of these vendor relationships at their negotiated transaction price, which is either at a discount or no cost.
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 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, 2020, 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, 2020, 2019 and 2018, no customer accounted for more than 10% of total revenue. As of December 31, 2020 and 2019, no customer had an accounts receivable balance greater than 10% of total accounts receivable. The Company believes that, as of December 31, 2020, 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. 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.
Operating Leases	Operating Leases In February 2016, the Financial Accounting Standards Board ("FASB") issued guidance that requires companies to present assets and liabilities arising from leases on the consolidated balance sheet. The updated standard aims to increase transparency and comparability among organizations by requiring lessees to recognize right of use ("ROU") assets and lease liabilities on the balance sheet and disclose key information about leasing arrangements. The Company adopted this standard on January 1, 2019 on a modified retrospective basis by applying the new standard to its lease portfolio as of January 1, 2019, while continuing to apply legacy guidance in the comparative periods. The Company enters into operating leases for real estate assets related to office space and co-location assets related to space or racks at co-location facilities and related equipment for its servers and other networking equipment. The Company determines if an arrangement contains a lease at the inception of a contract by assessing whether there is an identified asset and whether the contract conveys the right to control the use of the identified asset in exchange for consideration and the right to obtain the economic benefits from the use of the identified asset. Upon commencement of a lease, the Company records a right-of-use asset that represents the Company’s right to use the underlying asset for the lease term and a lease liability that represents an obligation to make lease payments arising from the lease. Right-of-use assets and lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. Lease payments are discounted at the lease commencement date. As the Company’s leases do not provide an implicit rate, an incremental borrowing rate has been applied based on the Company's credit-adjusted risk-free rate. The Company often enters into contracts that contain both lease and non-lease components. Real estate non-lease components include real estate taxes, insurance, maintenance, parking and other operating costs. Co-location non-lease components include utilities and other operating costs. The Company includes both lease and non-lease components of fixed costs in its lease arrangements as a single lease component. Variable costs, such as utilities based on actual usage, are not included in the measurement of right-of-use assets and lease liabilities but are expensed when the event determining the amount of variable consideration to be paid occurs. The Company’s lease terms often include renewal options and, particularly in the case of co-location arrangements, may include evergreen provisions. The Company’s right-of-use assets and lease liabilities generally do not include the options to extend, or terminate, unless it is reasonably certain that the Company will exercise these options. The Company has elected to exclude leases for certain networking equipment with terms of 12 months or less from its right-of-use assets and lease liabilities on its consolidated balance sheet. Lease expense is recognized on a straight-line basis over the expected lease term.
Equity Method Investments	Equity Method Investments The Company accounts for equity investments in which it has significant influence, but not a controlling financial interest, using the equity method of accounting. Under the equity method of accounting, investments are initially recorded at cost, less impairment, and subsequently adjusted to recognize the Company’s share of earnings or losses.
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 each year. As of December 31, 2020, 2019 and 2018, 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, 2020, 2019 and 2018. 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.
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; capitalization 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.
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 awards with market-based vesting conditions, the Company uses a Monte Carlo simulation to determine the fair value of the award. 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 operations.
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, 2020 and 2019, the fair value of the forward currency contracts and the underlying net gains for the years ended December 31, 2020, 2019 and 2018 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.
Income Taxes	Income 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 in the years during 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 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 based on technical merit, 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.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2020

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, valuation and useful lives of acquired intangible assets, 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.

Newly-Adopted Accounting Pronouncements and Recent Accounting Pronouncements

Newly-Adopted Accounting Pronouncements

In June 2016, the Financial Accounting Standards Board ("FASB") issued guidance that introduces a new methodology for accounting for credit losses on financial instruments. The guidance establishes a new "expected credit loss model" that requires entities to estimate current expected credit losses on financial instruments by using all practical and relevant information. Any expected credit losses are to be reflected as allowances. The Company prospectively adopted this standard on January 1, 2020. Adoption of the standard did not have a material impact on the Company's consolidated financial statements.

In August 2018, the FASB issued guidance that addresses a customer’s accounting for implementation costs incurred in a cloud computing arrangement that is a service contract. The guidance aligns the accounting for costs incurred to implement a cloud computing arrangement that is a service arrangement with the guidance for capitalizing costs associated with developing or obtaining internal-use software. The Company prospectively adopted this standard on January 1, 2020. Adoption of the standard did not have a material impact on the Company's consolidated financial statements.

Recent Accounting Pronouncements

In August 2020, the FASB issued guidance that is expected to reduce complexity and improve comparability of financial reporting associated with accounting for convertible instruments and contracts in an entity’s own equity. This guidance will be effective for the Company on January 1, 2022. The Company is evaluating the potential impact of adopting this new accounting guidance on its consolidated financial statements related to the accounting for convertible debt arrangements.

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 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 sheets.

The Company classifies its debt securities 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

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 which primarily consists of allowances for current expected credit losses. Increases and decreases in the allowance for current expected credit losses are included as a component of general and administrative expense in the consolidated statements of income. The allowance for current expected credit losses has been developed using historical loss rates for the previous twelve months as well as expectations about the future where the Company has been able to develop forecasts to support its estimates. In addition, the allowance considers outstanding balances on a customer-specific, account-by-account basis. The Company assesses collectibility 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.

Revenue Recognition, Incremental Costs to Obtain a Contract with a Customer, Contract Liabilities and Cost of Revenue

Incremental Costs to Obtain a Contract with a Customer

The Company capitalizes incremental costs associated with obtaining customer contracts, specifically certain commission and incentive payments. The Company pays commissions and incentives up-front based on contract value upon signing a new arrangement with a customer and upon renewal and upgrades of existing contracts with customers if the renewal and upgrades result in an incremental increase in contract value. To the extent commissions and incentives are earned, the expenses, including estimated payroll taxes, are deferred on the Company's consolidated balance sheet and amortized over the expected life of the customer arrangement on a straight-line basis. Based on the nature of the Company's unique technology and services, and the rate at which the Company continually enhances and updates its technology, the expected life of the customer arrangement is determined to be approximately 2.5 years. Additionally, the Company may pay commissions and incentives based upon contract value, rather than incremental increase in contract value, to certain sales groups within the Company. For these commission arrangements, the Company amortizes capitalized costs for contract renewals over an average renewal contract period of 16 months. The Company also incurs commission expense on an ongoing basis based upon revenue recognized. In these cases, no incremental costs are deferred, as the commissions are earned and expensed in the same period for which the associated revenue is recognized.

Amortization of the costs is primarily included in sales and marketing expense in the consolidated statements of income. The current portion of deferred commission and incentive payments is included in prepaid expenses and other current assets, and the long-term portion is included in other assets on the Company's consolidated balance sheets.

Contract Liabilities

Contract liabilities primarily represent payments received from customers for which the related performance obligations have not yet been satisfied. These balances consist of the unearned portion of monthly service fees and integration fees and prepayments made by customers for future periods. The current and long-term portions of the Company's contract liabilities are included in deferred revenue in the respective sections of the Company's consolidated balance sheets.

Revenue Recognition

The Company primarily derives revenue from the sale of services to customers executing contracts having terms of one year or longer. Services included in the Company's contracts consist of its core services – the delivery of content, applications and software over the internet – as well as security solutions and professional services. Revenue is recognized upon transfer of control of promised services in an amount that reflects the consideration the Company expects to receive in exchange for those services.

The Company enters into contracts that may include various combinations of these services, which are generally capable of being distinct and accounted for as separate performance obligations. These contracts generally commit the customer to a minimum of monthly, quarterly or annual levels of usage and specify the rate at which the customer must pay for actual usage

above the stated minimum. Based on the typical structure of the Company's contracts, which are generally for monthly recurring services that are essentially the same over time and have the same pattern of transfer to the customer, most performance obligations represent a promise to deliver a series of distinct services over time.

The Company's contracts with customers sometimes include promises to deliver multiple services to a customer. Determining whether services are distinct performance obligations often requires the exercise of judgment by management. For example, advanced features that enhance a service and are highly interrelated are generally not considered distinct; rather, they are combined with the service they relate to into one performance obligation. Different determinations related to combining services into performance obligations could result in differences in the timing and amount of revenue recognized in a period.

Generally, the transaction price in a contract is equal to the committed price stated in the contract, less any discounts or rebates. The Company's typical contracts qualify for series accounting, and the pricing terms generally do not require estimation of the transaction price beyond the reporting period. As a result, any incremental fees generated as a result of usage or “bursting” over committed contract levels are recorded in the period to which the services relate. The amount of consideration recognized for usage above contract minimums is limited to the amount the Company expects to be entitled to receive in exchange for providing the services. Once the transaction price has been determined, the Company allocates such price among all performance obligations in the contract on a relative standalone selling price (“SSP”) basis.

Determination of SSP requires the exercise of judgment by management. SSP is based on observable inputs such as the price the Company charges for the service when sold separately or the discounted list price per management’s approved price list. In cases where services are not sold separately or price list rates are not available, a cost-plus-margin approach or adjusted market approach is used to determine SSP.

Most content delivery and security services represent stand-ready obligations that are satisfied over time as the customer simultaneously receives and consumes the benefits provided by the Company. Accordingly, revenue for those services is recognized over time, generally ratably over the term of the arrangement due to consistent monthly traffic commitments that expire each period. Any bursting over given commitments is recognized in the period in which the traffic was served. For services that involve traffic consumption, revenue is recognized in an amount that reflects the level of traffic served to a customer in a given period. For custom arrangements, other methods may be used as a measure of progress towards satisfying the performance obligations.

Some of the Company's services are satisfied at a point in time, such as one-time professional services contracts, integration services and most license sales where the primary obligation is delivery of the license at the start of the term. In these cases, revenue is recognized at the point in time of delivery or satisfaction of the performance obligation.

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. Consideration payable to a customer is reviewed as part of the transaction price. If the payment to the customer does not represent payment for a distinct service, revenue is recognized only up to the net amount of consideration after customer payment obligations are considered. The Company may also resell the licenses or services of third parties. If the Company is acting as an agent in an arrangement with a customer to provide third party services, the transaction price reflects only the net amount to which the Company will be entitled, after accounting for payments made to the third party responsible for satisfying the performance obligation.

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 services delivery and network operation, build-out and support of the Company's network; 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 streamed by the Company for customers. The Company enters into contracts for bandwidth with third-party network providers with terms typically ranging from several months to five 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 to locate its servers and provide access to their bandwidth at a discount or no cost. Although the Company does not provide any goods or services to the ISPs or the ISPs’ customers under these arrangements, the ISPs and their customers indirectly benefit by accessing content through a local Company server, resulting in better content delivery. The Company records the cost of these vendor relationships at their negotiated transaction price, which is either at a discount or no cost.

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 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, 2020, 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, 2020, 2019 and 2018, no customer accounted for more than 10% of total revenue. As of December 31, 2020 and 2019, no customer had an accounts receivable balance greater than 10% of total accounts receivable. The Company believes that, as of December 31, 2020, its concentration of credit risk related to accounts receivable was not significant.

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 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. 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.

Operating Leases

In February 2016, the Financial Accounting Standards Board ("FASB") issued guidance that requires companies to present assets and liabilities arising from leases on the consolidated balance sheet. The updated standard aims to increase transparency and comparability among organizations by requiring lessees to recognize right of use ("ROU") assets and lease liabilities on the balance sheet and disclose key information about leasing arrangements. The Company adopted this standard on January 1, 2019 on a modified retrospective basis by applying the new standard to its lease portfolio as of January 1, 2019, while continuing to apply legacy guidance in the comparative periods.

The Company enters into operating leases for real estate assets related to office space and co-location assets related to space or racks at co-location facilities and related equipment for its servers and other networking equipment. The Company determines if an arrangement contains a lease at the inception of a contract by assessing whether there is an identified asset and whether the contract conveys the right to control the use of the identified asset in exchange for consideration and the right to obtain the economic benefits from the use of the identified asset.

Upon commencement of a lease, the Company records a right-of-use asset that represents the Company’s right to use the underlying asset for the lease term and a lease liability that represents an obligation to make lease payments arising from the lease. Right-of-use assets and lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. Lease payments are discounted at the lease commencement date. As the Company’s leases do not provide an implicit rate, an incremental borrowing rate has been applied based on the Company's credit-adjusted risk-free rate.

The Company often enters into contracts that contain both lease and non-lease components. Real estate non-lease components include real estate taxes, insurance, maintenance, parking and other operating costs. Co-location non-lease components include utilities and other operating costs. The Company includes both lease and non-lease components of fixed costs in its lease arrangements as a single lease component. Variable costs, such as utilities based on actual usage, are not included in the measurement of right-of-use assets and lease liabilities but are expensed when the event determining the amount of variable consideration to be paid occurs.

The Company’s lease terms often include renewal options and, particularly in the case of co-location arrangements, may include evergreen provisions. The Company’s right-of-use assets and lease liabilities generally do not include the options to extend, or terminate, unless it is reasonably certain that the Company will exercise these options. The Company has elected to exclude leases for certain networking equipment with terms of 12 months or less from its right-of-use assets and lease liabilities on its consolidated balance sheet.

Lease expense is recognized on a straight-line basis over the expected lease term.

Equity Method Investments

The Company accounts for equity investments in which it has significant influence, but not a controlling financial interest, using the equity method of accounting. Under the equity method of accounting, investments are initially recorded at cost, less impairment, and subsequently adjusted to recognize the Company’s share of earnings or losses.

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 each year. As of December 31, 2020, 2019 and 2018, 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, 2020, 2019 and 2018.

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.

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; capitalization 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.

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 awards with market-based vesting conditions, the Company uses a Monte Carlo simulation to determine the fair value of the award. 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 operations.

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, 2020 and 2019, the fair value of the forward currency contracts and the underlying net gains for the years ended December 31, 2020, 2019 and 2018 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.

Income 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 in the years during 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 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 based on technical merit, 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.