| Description of the Business and Summary of Significant Accounting Policies | Description of the Business and Summary of Significant Accounting Policies Business Dropbox, Inc. (the “Company” or “Dropbox”) is a global collaboration platform. Dropbox was incorporated in May 2007 as Evenflow, Inc., a Delaware corporation, and changed its name to Dropbox, Inc. in October 2009. The Company is headquartered in San Francisco, California. Basis of presentation and consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the United States of America generally accepted accounting principles (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission ("SEC") regarding interim financial reporting. The accompanying unaudited condensed consolidated financial statements include the accounts of Dropbox and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The condensed consolidated balance sheet as of December 31, 2017 included herein was derived from the audited financial statements as of that date. The unaudited condensed consolidated financial statements reflect all normal recurring adjustments necessary to present fairly the balance sheets, statements of operations, statements of comprehensive loss and the statements of cash flows for the interim periods, but are not necessarily indicative of the results of operations to be anticipated for the full fiscal year ended December 31, 2018 or any future period. The unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the related notes thereto as of and for the year ended December 31, 2017, included in the Company's prospectus filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended, on March 23, 2018, referred to as the Prospectus. Initial public offering and private placement On March 27, 2018, the Company closed its initial public offering ("IPO"), in which the Company issued and sold 26,822,409 shares of Class A common stock at $21.00 per share. The Company received aggregate proceeds of $538.2 million , net of underwriters' discounts and commissions, before deducting offering costs of $6.9 million , net of reimbursements. Immediately prior to the closing of the Company’s IPO, 147,310,563 shares of convertible preferred stock outstanding converted into an equivalent number of shares of Class B common stock. Further, pursuant to transfer agreements with certain of the Company’s stockholders, 258,620 shares of the Company’s convertible preferred stock and 2,609,951 shares of the Company’s Class B common stock automatically converted into an equivalent number of shares of Class A common stock. Immediately subsequent to the closing of the Company's IPO, Salesforce Ventures LLC purchased 4,761,905 shares of Class A common stock from the Company at $21.00 per share. The Company received aggregate proceeds of $100.0 million and did not pay any underwriting discounts or commissions with respect to the shares that were sold in the private placement. On March 28, 2018, the underwriters exercised their option to purchase an additional 5,400,000 shares of the Company's Class A common stock at $21.00 per share. This transaction closed on April 3, 2018, resulting in additional proceeds of $108.4 million , net of underwriters' discounts and commissions. The Company’s net proceeds from the IPO, the concurrent private placement, and underwriters' option totaled $ 746.6 million , before deducting offering costs of $ 6.9 million , net of reimbursements. Upon the effectiveness of the registration statement for the Company's IPO, which was March 22, 2018, the liquidity event-related performance vesting condition, referred to as the Performance Vesting Condition, associated with the Company's two-tier RSUs was satisfied. As a result, the Company recognized the cumulative unrecognized stock-based compensation related to its two-tier restricted stock units ("RSUs") using the accelerated attribution method of $418.7 million attributable to service prior to such effective date. As of September 30, 2018 , the remaining unamortized stock-based compensation related to the two-tier RSUs was $0.4 million , which will be recognized if the requisite service is provided over a weighted average period of 0.3 years. During the first quarter of 2018, the Company's Board of Directors approved the acceleration of the Performance Vesting Condition for which the service condition was satisfied, to occur upon the effectiveness of the registration statement for the Company's IPO, rather than six months following an IPO. As a result, the Company released 26.8 million shares of common stock underlying the two-tier RSUs for which the Performance Vesting Condition was satisfied, and recorded $13.9 million in employer related payroll tax expenses associated with these same awards. See “—Stock-based compensation” for further discussion regarding the Company's two-tier RSUs. Stock split On March 7, 2018, the Company effected a 1-for-1.5 reverse stock split of its capital stock. All of the share and per share information referenced throughout the condensed consolidated financial statements and notes to the condensed consolidated financial statements have been retroactively adjusted to reflect this reverse stock split. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the Company’s condensed consolidated financial statements and accompanying notes. These estimates are based on information available as of the date of the condensed consolidated financial statements. Management evaluates these estimates and assumptions on a regular basis. Actual results may differ materially from these estimates. The Company’s most significant estimates and judgments involve recognition of revenue, the measurement of the Company’s stock-based compensation, including the estimation of the underlying deemed fair value of common stock in periods prior to the date of the Company's IPO, the estimation of the fair value of market-based awards, and the valuation of acquired intangible assets and goodwill from business combinations. Financial information about segments and geographic areas The Company manages its operations and allocates resources as a single operating segment. Further, the Company manages, monitors, and reports its financials as a single reporting segment. The Company’s chief operating decision-maker is its Chief Executive Officer, who reviews financial information presented on a consolidated basis for purposes of making operating decisions, assessing financial performance, and allocating resources. See Note 13, "Geographic Areas" for information regarding the Company’s long-lived assets and revenue by geography. Foreign currency transactions The assets and liabilities of the Company’s foreign subsidiaries are translated from their respective functional currencies into U.S. dollars at the exchange rates in effect at the balance sheet date. Revenue and expense amounts are translated at the average exchange rate for the period. Foreign currency translation gains and losses are recorded in other comprehensive income (loss). Gains and losses realized from foreign currency transactions (those transactions denominated in currencies other than the foreign subsidiaries’ functional currency) are included in other income (expense), net. Monetary assets and liabilities are remeasured using foreign currency exchange rates at the end of the period, and non-monetary assets are remeasured based on historical exchange rates. The Company recorded net foreign currency transaction losses of $ 1.0 million and $ 1.4 million during the three and nine months ended September 30, 2018 , respectively, and net foreign currency transaction gains of $2.9 million and $ 6.9 million during the three and nine months ended September 30, 2017 , respectively. Revenue recognition The Company derives its revenue from subscription fees from customers for access to its platform. The Company’s policy is to exclude sales and other indirect taxes when measuring the transaction price of its subscription agreements. The Company accounts for revenue contracts with customers through the following steps: • Identification of the contract, or contracts, with a customer • Identification of the performance obligations in the contract • Determination of the transaction price • Allocation of the transaction price to the performance obligations in the contract • Recognition of revenue when, or as, the Company satisfies a performance obligation The Company’s subscription agreements generally have monthly or annual contractual terms and a small percentage have multi-year contractual terms. Revenue is recognized ratably over the related contractual term beginning on the date that the platform is made available to a customer. Access to the platform represents a series of distinct services as the Company continually provides access to, and fulfills its obligation to the end customer over the subscription term. The series of distinct services represents a single performance obligation that is satisfied over time. The Company recognizes revenue ratably because the customer receives and consumes the benefits of the platform throughout the contract period. The Company’s contracts are generally non-cancelable. The Company bills in advance for monthly contracts and typically bills annually in advance for contracts with terms of one year or longer . The Company also recognizes an immaterial amount of contract assets, or unbilled receivables, primarily relating to consideration for services completed but not billed at the reporting date. Unbilled receivables are classified as receivables when the Company has the right to invoice the customer. The Company records contract liabilities when cash payments are received or due in advance of performance to deferred revenue. Deferred revenue primarily relates to the advance consideration received from the customer. The price of subscriptions is generally fixed at contract inception and therefore, the Company’s contracts do not contain a significant amount of variable consideration. As a result, the amount of revenue recognized in the periods presented from performance obligations satisfied (or partially satisfied) in previous periods was not material. The Company recognized $213.2 million and $390.1 million of revenue during the three and nine months ended September 30, 2018 , respectively, and recognized $178.0 million and $324.6 million of revenue during the three and nine months ended September 30, 2017 , respectively, that was included in the deferred revenue balances at the beginning of their respective periods. As of September 30, 2018 , future estimated revenue related to performance obligations that were unsatisfied or partially unsatisfied was $523.3 million . The substantial majority of the unsatisfied performance obligations will be satisfied over the next twelve months. Stock-based compensation The Company has granted RSUs to its employees and members of the Board of Directors under the 2008 Equity Incentive Plan (“2008 Plan”), the 2017 Equity Incentive Plan (“2017 Plan”), and the 2018 Equity Incentive Plan ("2018 Plan"). The Company had two types of RSUs outstanding as of September 30, 2018 : • One-tier RSUs, which have a service-based vesting condition over a four -year period. These awards typically have a cliff vesting period of one year and continue to vest quarterly thereafter. The Company began granting one-tier RSUs under its 2008 Plan in August 2015 and it continues to grant one-tier RSUs under its 2018 Plan. The Company recognizes compensation expense associated with one-tier RSUs ratably on a straight-line basis over the requisite service period and accounts for forfeitures in the period in which they occur. • Two-tier RSUs, which have both a service-based vesting condition and a Performance Vesting Condition. The service-based vesting period for these awards is typically four years with a cliff vesting period of one year and continue to vest monthly thereafter. Upon satisfaction of the Performance Vesting Condition, these awards vest quarterly. The Performance Vesting Condition is satisfied on the earlier of (i) an acquisition or change in control of the Company or (ii) the earlier of (a) six months after the Company’s initial public offering or (b) March 15 of the year following the Company’s initial public offering. During the first quarter of 2018, the Company's Board of Directors approved the acceleration of the Performance Vesting Condition for which the service condition was satisfied, to occur upon the effectiveness of the registration statement related to the Company's IPO. Prior to August 2015, the Company granted two-tier RSUs under the 2008 Plan. The last grant date for two-tier RSUs was in May 2015. The Company recognizes compensation expense associated with two-tier RSUs using the accelerated attribution method over the requisite service period. The Performance Vesting Condition for the two-tier RSUs was satisfied upon the effectiveness of the registration statement related to the Company's IPO, which was March 22, 2018. On that date, the Company recognized the cumulative unrecognized expense of the two-tier RSUs, using the accelerated attribution method, which is included in the Company's results for the nine months ended September 30, 2018 . See "—Initial public offering and private placement” for further discussion. As of September 30, 2018 , the remaining unamortized stock-based compensation related to the two-tier RSUs was $0.4 million , which will be recognized if the requisite service is provided over a weighted average period of 0.3 years. Since August 2015, the Company has granted RSUs as the only stock-based payment awards to its employees, with the exception of awards granted to its co-founders, and has not granted any stock options since then. The fair values of the common stock underlying the RSUs granted in periods prior to the date of the Company's IPO were determined by the Board of Directors, with input from management and contemporaneous third-party valuations, which were performed at least quarterly. For valuations after the Company's IPO, the Board of Directors will determine the fair value of each share of underlying common stock based on the closing price of the Company's Class A common stock as reported on the Nasdaq Global Select Market on the date of the grant. In December 2017, the Board of Directors approved a grant to the Company’s co-founders of restricted stock awards (“RSAs”) with respect to 14.7 million shares of Class A Common Stock in the aggregate (collectively, the “Co-Founder Grants”), of which 10.3 million RSAs were granted to Mr. Houston, the Company’s co-founder and Chief Executive Officer, and 4.4 million RSAs were granted to Mr. Ferdowsi, the Company’s co-founder and Director. These Co-Founder Grants have service-based, market-based, and performance-based vesting conditions. The Co-Founder Grants comprise nine tranches that are eligible to vest based on the achievement of stock price goals, or, each, a Stock Price Target. The Company estimated the grant date fair value of the Co-Founder Grants using a model based on multiple stock price paths developed through the use of a Monte Carlo simulation that incorporates into the valuation the possibility that the Stock Price Targets may not be satisfied. The average grant date fair value of each Co-Founder Grant was estimated to be $10.60 per share, and the Company will recognize aggregate stock-based compensation expense of $156.2 million over the requisite service period of each tranche, which ranged from 2.9 to 6.9 years, using the accelerated attribution method. If the Stock Price Targets are met sooner than the derived service period, the Company will adjust its stock-based compensation to reflect the cumulative expense associated with the vested awards. The Company will recognize expense if the requisite service is provided, regardless of whether the market conditions are achieved. The Co-Founder Grants contain an implied performance-based vesting condition because the Stock Price Targets are based on the trailing 30-day average price of the shares from an established national securities exchange or automated quotation system. Accordingly, no vesting could occur until the completion of the Company’s IPO. The relevant performance-based vesting condition for the Co-Founder Grants was satisfied on the date the Company’s shares of Class A common stock commenced trading on the Nasdaq Global Select Market, in connection with the Company’s IPO, which was March 23, 2018. The Company recognized $8.8 million and $28.1 million in stock-based compensation related to the Co-Founder Grants during the three and nine months ended September 30, 2018 , respectively. Cash and cash equivalents Cash consists primarily of cash on deposit with banks and includes amounts in transit from payment processors for credit and debit card transactions, which typically settle within five business days. Cash equivalents include highly liquid investments purchased with an original maturity date of 90 days or less from the date of purchase. Short-term investments The Company’s short-term investments are primarily comprised of corporate notes and obligations, U.S. treasury securities, certificates of deposits, U.S. agency obligations, and commercial paper. The Company determines the appropriate classification of its short-term investments at the time of purchase and reevaluates such designation at each balance sheet date. The Company has classified and accounted for its short-term investments as available-for-sale securities as the Company may sell these securities at any time for use in its current operations or for other purposes, even prior to maturity. As a result, the Company classifies its short-term investments, including securities with stated maturities beyond twelve months, within current assets in the condensed consolidated balance sheets. The Company's short-term investments are classified as available-for-sale securities and are recorded at fair value each reporting period. Unrealized gains and losses on these short-term investments are reported as a separate component of accumulated other comprehensive income (loss) in the condensed consolidated balance sheets until realized. Interest income is reported within interest income (expense), net in the condensed consolidated statements of operations. The Company periodically evaluates its short-term investments to assess whether those with unrealized loss positions are other-than-temporarily impaired. The Company considers various factors in determining whether to recognize an impairment charge, including the length of time the investment has been in a loss position, the extent to which the fair value is less than the Company’s cost basis, and the financial condition and near-term prospects of the investee. Realized gains and losses are determined based on the specific identification method and are reported in other income (expense), net in the condensed consolidated statements of operations. If the Company determines that the decline in an investment’s fair value is other-than-temporary, the difference is recognized as an impairment loss in the condensed consolidated statements of operations. Concentrations of credit risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, accounts receivable, and short-term investments. The Company places its cash and cash equivalents and short-term investments with well-established financial institutions. Trade accounts receivables are typically unsecured and are derived from revenue earned from customers located around the world. Two customers accounted for 13% and 40% of total trade and other receivables, net as of September 30, 2018 . Two customers accounted for 18% and 27% of total trade and other receivables, net as of December 31, 2017 . No customer accounted for more than 10% of the Company’s revenue in the periods presented. Non-trade receivables The Company records non-trade receivables to reflect amounts due for activities outside of its subscription agreements. Historically, the Company’s non-trade receivables have related primarily to receivables resulting from tenant improvement allowances. Non-trade receivables totaled $44.8 million and $5.2 million , as of September 30, 2018 and December 31, 2017 , respectively, and are classified within prepaid expenses and other current assets and other assets in the accompanying condensed consolidated balance sheets. The Company recognized its initial tenant improvement allowance receivable related to its new corporate headquarters once it took initial possession of the first phase in June 2018. As of September 30, 2018 , $40.5 million is included in prepaid expenses and other current assets related to this tenant improvement allowance receivable. See "—Lease obligations” for further discussion on the corresponding recording of the lease incentive obligation. Deferred commissions, net Deferred commissions, net is stated as gross deferred commissions less accumulated amortization. Sales commissions earned by the Company’s sales force and third-party resellers, as well as related payroll taxes, are considered to be incremental and recoverable costs of obtaining a contract with a customer. These amounts have been capitalized as deferred commissions within prepaid and other current assets and other assets on the condensed consolidated balance sheets. The Company deferred incremental costs of obtaining a contract of $ 7.4 million and $ 24.9 million during the three and nine months ended September 30, 2018 , respectively, and $ 6.3 million and $ 16.0 million during the three and nine months ended September 30, 2017 , respectively. Deferred commissions, net included in prepaid and other current assets were $13.0 million and $8.1 million as of September 30, 2018 and December 31, 2017 , respectively. Deferred commissions, net included in other assets were $36.3 million and $24.8 million as of September 30, 2018 and December 31, 2017 , respectively. Deferred commissions are amortized over a period of benefit of five years. The period of benefit was estimated by considering factors such as historical customer attrition rates, the useful life of the Company’s technology, and the impact of competition in its industry. Amortized costs were $ 3.2 million and $ 8.5 million for the three and nine months ended September 30, 2018 , respectively, and $ 2.0 million and $ 4.6 million for the three and nine months ended September 30, 2017 , respectively. Amortized costs are included in sales and marketing expense in the accompanying condensed consolidated statements of operations. There was no impairment loss in relation to the deferred costs for any period presented. Property and equipment, net Equipment is stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful life of the related asset, which is generally three to seven years. Leasehold improvements are amortized on a straight-line basis over the shorter of their estimated useful lives or the term of the related lease. In the first quarter of 2018, the Company determined that the useful lives of certain infrastructure equipment, which are depreciated through cost of revenue, should be increased from three to four years. The Company accounted for this as a change in estimate that was applied prospectively, effective as of January 1, 2018. This change in useful life resulted in a reduction in depreciation expense within cost of revenue of $2.8 million and $13.6 million during the three and nine months ended September 30, 2018 , respectively. The following table presents the estimated useful lives of property and equipment: Property and equipment Useful life Buildings 20 to 30 years Datacenter and other computer equipment 3 to 5 years Office equipment and other 3 to 7 years Leasehold improvements Lesser of estimated useful life or remaining lease term Lease obligations The Company leases office space, datacenters, and equipment under non-cancelable capital and operating leases with various expiration dates through 2033. Certain of the Company’s operating lease agreements contain tenant improvement allowances from its landlords. These allowances are accounted for as lease incentive obligations and are amortized as reductions to rent expense over the lease term. In June 2018, the Company took initial possession of the first phase of its new corporate headquarters and recorded a lease incentive obligation related to this phase. As of September 30, 2018 , $2.6 million was included in accrued and other current liabilities and $37.0 million was included in deferred rent, non-current in the Company's condensed consolidated balance sheets. In addition, certain of the operating lease agreements contain rent concession, rent escalation, and option to renew provisions. Rent concession and rent escalation provisions are considered in determining the straight-line rent expense to be recorded over the lease term. Lease expense is recognized on a straight-line basis over the lease term commencing on the date the Company has the right to use the leased property. The Company does not assume renewals in its determination of the lease term unless the renewals are deemed to be reasonably assured at lease inception. In 2012, the Company undertook a series of structural improvements to the floor that it occupied in its previous corporate headquarters. As a result of the requirement to fund construction costs and its responsibility for cost overruns during the construction period, the Company was considered the deemed owner of the floor for accounting purposes. Due to the presence of a standby letter of credit as a security deposit, the Company was deemed to have continuing involvement after the construction period. As such, it accounted for this arrangement as owned real estate and recorded a building asset and an imputed financing obligation for its liability to the legal owners. In September 2018, the Company terminated its master lease for its previous corporate headquarters, the impact of which is described in Note 4, "Property and Equipment, Net". The Company leases certain equipment from various third parties, including from a related party, through equipment financing leases under capital leases. See Note 12, “Related Party Transactions” for additional details. These leases either include a bargain purchase option, a full transfer of ownership at the completion of the lease term, or the terms of the leases are at least 75 percent of the useful lives of the assets and are therefore classified as capital leases. These leases are capitalized in property and equipment and the related amortization of assets under capital leases is included in depreciation and amortization expense in the Company’s condensed consolidated statements of operations. Initial asset values and lease obligations are based on the present value of future minimum lease payments. Long-lived assets, including goodwill and other acquired intangible assets, net The Company evaluates the recoverability of its property and equipment and finite-lived intangible assets for possible impairment whenever events or circumstances indicate that the carrying amount of such assets may not be recoverable. The evaluation is performed at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. Recoverability of these assets is measured by a comparison of the carrying amounts to the future undiscounted cash flows the assets are expected to generate. If such review determines that the carrying amount of specific property and equipment or intangible assets is not recoverable, the carrying amount of such assets is reduced to its fair value. The Company reviews goodwill for impairment at least annually in the fourth quarter, or more frequently if events or changes in circumstances would more likely than not reduce the fair value of its single reporting unit below its carrying value. The Company has not recorded impairment charges on property and equipment, goodwill, or intangible assets for the periods presented in these condensed consolidated financial statements. Acquired property and equipment and finite-lived intangible assets are amortized over their useful lives. The Company evaluates the estimated remaining useful life of these assets when events or changes in circumstances warrant a revision to the remaining period of amortization. If the Company revises the estimated useful life assumption for any asset, the remaining unamortized balance is amortized or depreciated over the revised estimated useful life on a prospective basis. See "—Property and equipment, net” for further discussion regarding a change in useful life applied during the nine months ended September 30, 2018 . Income taxes Deferred income tax balances reflect the effects of temporary differences between the financial reporting and tax bases of the Company’s assets and liabilities using enacted tax rates expected to apply when taxes are actually paid or recovered. In addition, deferred tax assets are recorded for net operating loss and credit carryforwards. A valuation allowance is provided against deferred tax assets unless it is more likely than not that they will be realized based on all available positive and negative evidence. Such evidence includes, but is not limited to, recent cumulative earnings or losses, expectations of future taxable income by taxing jurisdiction, and the carry-forward periods available for the utilization of deferred tax assets. The Company uses a two-step approach to recognizing and measuring uncertain income tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates it is more likely than not that the position will be sustained on audit. The second step is to measure the tax benefit as the largest amount which is more than 50% likely of being realized upon ultimate settlement. The Company recognizes interest and penalties related to unrecognized tax benefits as income tax expense. Although the Company believes that it has adequately reserved for its uncertain tax positions, it can provide no assurance that the final tax outcome of these matters will not be materially different. The Company evaluates its uncertain tax positions on a regular basis and evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, such as the 2017 Tax Cuts and Jobs Act ("2017 Tax Reform Act"), correspondence with tax authorities during the course of an audit, and effective settlement of audit issues. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will affect the provision for income taxes in the period in which such determination is made and could have a material impact on the Company’s financial condition and results of operations. Fair value measurement The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. The Company defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value measurements for assets and liabilities, the Company considers the principal or most advantageous market in which it would transact and the market-based risk measurements or assumptions that market participants would use in pricing the asset or liability, such as risks inherent in valuation techniques, transfer restrictions, and credit risk. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Observable inputs other than quoted prices in active markets for identica |
