Basis of Presentation (Policies)	3 Months Ended
Basis of Presentation (Policies)	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Nature of Operations	The Company and Nature of Operations FalconStor Software, Inc., a Delaware Corporation (the "Company"), is a leading software-defined storage company offering a converged data services software platform that is hardware agnostic. The Company develops, manufactures and sells data migration, business continuity, disaster recovery, optimized backup and de-duplication solutions and provides the related maintenance, implementation and engineering services.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. The Company’s significant estimates include those related to revenue recognition, accounts receivable allowances, share-based payment compensation, valuation of derivatives, capitalizable software development costs, valuation of goodwill and other intangible assets and income taxes. Actual results could differ from those estimates. The financial market volatility in many countries where the Company operates has impacted and may continue to impact the Company’s business. Such conditions could have a material impact on the Company’s significant accounting estimates discussed above.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying unaudited interim condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations relating to interim financial statements. In the opinion of management, the accompanying unaudited interim condensed consolidated financial statements reflect all adjustments, consisting only of normal recurring adjustments, necessary to present fairly the financial position of the Company at March 31, 2017, and the results of its operations for the three months ended March 31, 2017 and 2016. The results of operations of any interim period are not necessarily indicative of the results of operations to be expected for the full fiscal year. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes set forth in the Company's Annual Report on Form 10-K for the year ended December 31, 2016 ("2016 Form 10-K").
Recently Adopted and Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements In March 2016, the Financial Accounting Standards Board ("FASB") issued new guidance on accounting for employee share-based payment awards to simplify the accounting related to several aspects of accounting for share-based payment transactions, including income tax consequences of share-based payment transactions, classification of awards as either equity or liabilities, forfeitures, and classification on the statement of cash flows. The Company adopted this guidance as of January 1, 2017. In accordance with this new guidance the Company has made an entity-wide accounting policy election to account for forfeitures when they occur. As a result of this election, the Company recognized additional stock-based compensation expense of approximately $0.1 million in the first quarter of 2017 to adjust for actual forfeitures on historical share-based payment awards. In January 2017, the FASB issued new guidance on accounting for goodwill to simplify the goodwill impairment test by eliminating Step 2 of the goodwill impairment test. This new guidance also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. The new standard is effective for the annual period beginning after December 15, 2019, including interim reporting periods within that period, which for the Company is the annual period ending December 31, 2020. Early adoption is permitted. The Company elected to adopt this guidance as of January 1, 2017, prospectively for impairment tests performed subsequent to January 1, 2017. The Company's single reporting unit for purposes of its goodwill impairment test has a negative carrying value of $13.8 million as of March 31, 2017 and thus the Company determined there has been no impairment of goodwill. The adoption of this guidance did not have an impact on the Company's financial statements and related disclosures.
Revenue Recognition	Revenue Recognition The Company derives its revenue from sales of its products, support and services. Product revenue consists of the Company’s software integrated with industry standard hardware and sold as complete turn-key integrated solutions, as stand-alone software applications or sold on a subscription or consumption basis. Depending on the nature of the arrangement revenue, related to turn-key solutions and stand-alone software applications are generally recognized upon shipment and delivery of license keys. For certain arrangements revenue is recognized based on usage or ratably over the term of the arrangement. Support and services revenue consists of both maintenance revenues and professional services revenues. Revenue is recorded net of applicable sales taxes. In accordance with the authoritative guidance issued by the FASB on revenue recognition, the Company recognizes revenue when persuasive evidence of an arrangement exists, the fee is fixed or determinable, delivery has occurred, and collection of the resulting receivable is deemed probable. Products delivered to a customer on a trial basis are not recognized as revenue until the trial period has ended and acceptance has occurred by the customer. Reseller and distributor customers typically send the Company a purchase order when they have an end user identified. For bundled arrangements that include either maintenance or both maintenance and professional services, the Company uses the residual method to determine the amount of product revenue to be recognized. Under the residual method, consideration is allocated to the undelivered elements based upon VSOE of the fair value of those elements, with the residual of the arrangement fee allocated to and recognized as product revenue. If VSOE does not exist for all undelivered elements of an arrangement, the Company recognizes total revenue from the arrangement ratably over the term of the maintenance agreement. The Company's long-term portion of deferred revenue consists of (i) payments received for maintenance contracts with terms in excess of one year as of the balance sheet date, and (ii) payments received for product sales bundled with multiple years of maintenance but for which VSOE did not exist for all undelivered elements of the arrangement. The Company provides an allowance for product returns as a reduction of revenue, based upon historical experience and known or expected trends. When more than one element, such as hardware, software and services are contained in a single arrangement, the Company will first allocate revenue based upon the relative selling price into two categories: (1) non-software components, such as hardware and any hardware-related items, as required system software that functions with the hardware to deliver the essential functionality of the hardware and related post-contract customer support, and software as service subscriptions and (2) software components and applications, such as post-contract customer support and other services. The Company will then allocate revenue within the non-software category to each element based upon their relative selling price using a hierarchy of VSOE, third-party evidence of selling price (“TPE”) or estimated selling prices (“ESP”), if VSOE or TPE does not exist. The Company will allocate revenue within the software category to the undelivered elements based upon their fair value using VSOE with the residual revenue allocated to the delivered elements. If the Company cannot objectively determine the VSOE of the fair value of any undelivered software element, the Company will defer revenue for all software components until all elements are delivered and services have been performed, until fair value can objectively be determined for any remaining undelivered elements, or until software maintenance is the only undelivered element which the Company does not have VSOE for, in which case revenue is recognized over the maintenance term for all software elements. Revenues associated with maintenance services are deferred and recognized as revenue ratably over the term of the contract. Revenues associated with software implementation and software engineering services are recognized when the services are performed. Costs of providing these services are included in cost of support and services. The Company has entered into various distribution, licensing and joint promotion agreements with OEMs, whereby the Company has provided the OEM a non-exclusive software license to install the Company’s software on certain hardware or to resell the Company’s software in exchange for payments based on the products distributed by these OEMs. Such payments from the OEM or distributor are recognized as revenue in the period reported by the OEM. From time to time the Company will enter into funded software development arrangements. Under such arrangements, revenue recognition will not commence until final delivery and/or acceptance of the product. For arrangements where the Company has VSOE for the undelivered elements, the Company will follow the residual method and recognize product revenue upon final delivery and/or acceptance of the product. For arrangements where the Company does not have VSOE for the undelivered elements, the Company will recognize the entire arrangement fee ratably commencing at the time of final delivery and/or acceptance through the end of the service period in the arrangement. Certain arrangements, for which VSOE of fair value for the undelivered maintenance elements cannot be established, are accounted for as a single unit of account. The revenue recognized from single units of accounting are typically allocated and classified on the consolidated statements of operations as product revenue and support and services revenue. Since VSOE cannot be established, VSOE of similar maintenance offerings provides the basis for the support and services revenue classification, and the remaining residual consideration provides the basis for the product revenue classification.
Substantial Doubt about Going Concern [Text Block]	Going Concern A fundamental principle of the preparation of financial statements in accordance with accounting principles generally accepted in the United States of America ("GAAP") is the assumption that an entity will continue in existence as a going concern, which contemplates continuity of operations and the realization of assets and settlement of liabilities occurring in the ordinary course of business. This principle is applicable to all entities except for entities in liquidation or entities for which liquidation appears imminent. In accordance with this requirement, the Company has prepared its consolidated financial statements on a going concern basis. The Company has incurred significant operating losses in the previous eight years and negative cash flow from operations in five of the previous eight years. The Company currently has a working capital deficiency of $12.1 million, which is inclusive of current deferred revenue of $15.8 million and a stockholders' deficit of $22.8 million. During the three months ended March 31, 2017, the Company incurred a net loss of $1.1 million and cash flow from operations of $0.1 million. The Company's total cash balance at March 31, 2017 was $3.4 million, an increase of less than $0.1 million as compared to December 31, 2016. In addition to these financial metrics, as of December 31, 2016, the Company was not in compliance with the financial covenants of the Series A redeemable convertible preferred stock, which were mutually agreed to annually, for two consecutive quarters. This breach provides the holder of the Series A redeemable convertible preferred stock with the right to require the Company to redeem any of the Series A redeemable convertible preferred stock at the greater of 100% of the stated value plus accrued and unpaid dividends or the product of the number of shares of common stock underlying the Series A redeemable convertible preferred stock and the closing price of the Company's common stock as of December 31, 2016. To date, the holder of the Series A redeemable convertible preferred stock has neither exercised nor waived this right and accordingly this right may be exercised at any time. In addition, the holders of the Series A redeemable convertible preferred stock have the right to request a redemption of the Series A redeemable convertible preferred stock on or after August 5, 2017. If the holders request that the Series A redeemable convertible preferred stock be redeemed, the Company may not have sufficient liquidity to undertake the redemption. If the Company does not redeem the Series A redeemable convertible preferred stock, the holder of the Series A redeemable convertible preferred stock can pursue other remedies. Refer to Note (11) Series A Redeemable Convertible Preferred Stock for further discussion regarding these other remedies. The Company's reduced cash balance and history of losses both in and of itself, and in combination with the redemption rights of the holders of the Series A redeemable convertible preferred stock, raise substantial doubt about the Company's ability to continue as a going concern within one year after May 5, 2017 (the date that these financial statements were issued). The Company's ability to continue as a going concern, including in the event of a redemption request by the holder, depends on its ability to execute its business plan, increase revenue and billings and reduce expenditures. During 2016, the Company continued to focus on aligning its expense structure with revenue expectations which included tighter expense controls and overall operational efficiencies which better align the Company's current business plan on a run-rate basis. These efficiencies include among other items, stream-lined personnel related costs and global overhead costs and efficiencies realized on the Company's redesigned go-to-market coverage models. These expense reduction initiatives continued throughout the first quarter of 2017 but to a lesser extent. The Company's worldwide headcount was 165 employees as of March 31, 2017, compared with 166 and 226 employees as of December 31, 2016 and 2015, respectively. Although, these reductions in operating expenses directly related to the Company achieving its goal of being cash flow positive for the first quarter of 2017, the Company's bookings, billings and revenue continued to decline which negatively impacts the Company's ability to continue as a going concern. There is no assurance that the Company will be successful in generating sufficient bookings, billings, revenue or continue to reduce operating costs. In addition, if the Company continues to incur losses, the Company may need to seek additional financing and there can be no assurance that the Company will be able to obtain financing or that such financing will be on favorable terms. Any such financing could be dilutive to our shareholders. Failure to generate sufficient revenue, billings, control or reduce expenditures and/or the inability to obtain financing will result in an inability of the Company to continue as a going concern.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	Share-Based Payments The Company accounts for share-based payments in accordance with the authoritative guidance issued by the FASB on share-based compensation, which establishes the accounting for transactions in which an entity exchanges its equity instruments for goods or services. Under the provisions of the authoritative guidance, share-based compensation expense is measured at the grant date, based on the fair value of the award, and is recognized as an expense over the requisite employee service period (generally the vesting period), net of actual forfeitures. For share-based payment awards that contain performance criteria share-based compensation, expense is recorded when the achievement of the performance condition is considered probable of achievement and is recorded on a straight-line basis over the requisite service period. If such performance criteria are not met, no compensation cost is recognized and any recognized compensation cost is reversed. The Company estimates the fair value of share-based payments using the Black-Scholes option-pricing model or the Monte Carlo simulation model if a market condition exists. Share-based compensation expense for a share-based payment award with a market condition is recorded on a straight-line basis over the longer of the explicit service period or the service period derived from the Monte Carlo simulation. Additionally, share-based awards to non-employees are expensed over the period in which the related services are rendered at their fair value. All share-based awards are expected to be fulfilled with new shares of common stock.
Goodwill and Intangible Assets, Policy [Policy Text Block]	Goodwill and Other Intangible Assets Goodwill represents the excess of the purchase price over the estimated fair value of net tangible and identifiable intangible assets acquired in business combinations. The Company has not amortized goodwill related to its acquisitions, but instead tests the balance for impairment. The Company evaluates goodwill for impairment annually or more frequently when an event occurs or circumstances change that indicate that the carrying value may not be recoverable. The Company tests goodwill for impairment by comparing the book value of net assets to the fair value of the reporting unit. If the fair value is determined to be less than the book value, the computed difference represents the amount of impairment. The Company's single reporting unit for purposes of its goodwill impairment test has a negative carrying value of $13.8 million as of March 31, 2017 and thus the Company has determined there was no impairment of goodwill.