Basis of Presentation (Policies)	3 Months Ended
Basis of Presentation (Policies)	Mar. 31, 2019
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" or "FalconStor"), is a leading storage software 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 accounting principles generally accepted in the United States of America ("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. During the first quarter of 2018, the Company also had significant estimates in the determination of the fair value of Series A Preferred Stock, notes payable and warrants issued. 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, 2019, and the results of its operations for the three months ended March 31, 2019 and 2018. 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, 2018 ("2018 Form 10-K").
Recently Adopted and Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (the "FASB") issued ASU No. 2016-02, which establishes a right-of-use (ROU) model that requires a lessee to record a right of use (ROU) asset and a lease liability on the balance sheet for most leases. In July 2018, the FASB issued ASU No. 2018-11, which amends the guidance to add a method of adoption whereby the issuer may elect to recognize a cumulative effect adjustment at the beginning of the period of adoption. ASU No. 2018-11 does not require comparative period financial information to be adjusted. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. ASU 2016-02 defines a lease as a contract, or part of a contract, that conveys the right to control the use of identified property, plant or equipment for a period of time in exchange for consideration. To determine whether a contract conveys the right to control the use of the identified asset for a period of time, the customer has to have both (1) the right to obtain substantially all of the economic benefits from the use of the identified asset and (2) the right to direct the use of the identified asset, a contract does not contain an identified asset if the supplier has a substantive right to substitute such asset ("the leasing criteria"). We have determined that our real estate leases with terms in excess of one year and which do not include an option to purchase the underlying asset, meet the leasing criteria. On January 1, 2019, we adopted ASU No. 2016-02, applying the package of practical expedients to leases that commenced before the effective date whereby we elected to not reassess the following: (i) whether any expired or existing contracts contain leases; (ii) the lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases. We elected to apply the transition provisions as of January 1, 2019, the date of adoption, and we recorded lease ROU assets of $2.9 million and related liabilities of $3.6 million million on our balance sheet related to our operating leases. We have no financing leases. There was no change to our consolidated statements of operations or cash flows. In July 2018, the FASB issued ASU 2018-09, Codification Improvements. The amendments in ASU 2018-09 affect a wide variety of Topics in the FASB Codification and apply to all reporting entities within the scope of the affected accounting guidance. The Company has evaluated ASU 2018-09 in its entirety and determined that the amendments related to Topic 718-740, Compensation-Stock Compensation-Income Taxes, are the only provisions that currently apply to the Company. The amendments in ASU 2018-09 related to Topic 718-740, Compensation-Stock Compensation-Income Taxes, clarify that an entity should recognize excess tax benefits related to stock compensation transactions in the period in which the amount of the deduction is determined. On January 1, 2019, we adopted ASU 2018-09 and it did not have a material impact on the Company's Condensed Consolidated Financial Statements. In June 2018, the FASB issued ASU 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, to expand the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees and supersedes the guidance in Subtopic 505-50, Equity - Equity-Based Payments to Non-Employees. Under ASU 2018-07, equity-classified nonemployee share-based payment awards are measured at the grant date fair value on the grant date. The probability of satisfying performance conditions must be considered for equity-classified nonemployee share-based payment awards with such conditions. On January 1, 2019, we adopted ASU 2018-07 and it did not have a material impact on the Company's Condensed Consolidated Financial Statements. In February 2018, the FASB issued ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, which provides entities the option to reclassify tax effects stranded in accumulated other comprehensive income as a result of the 2017 Tax Cuts and Jobs Act (“the Tax Act”) to retained earnings. On January 1, 2019, we adopted ASU 2018-02 and it did not have a material impact on the Company's Condensed Consolidated Financial Statements. (g) Recently Issued Accounting Pronouncements In August 2018, the FASB issued ASU 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General: Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans. The objective of the guidance is to improve the effectiveness of disclosure requirements on defined benefit pension plans and other postretirement plans. The guidance is effective for fiscal years beginning after December 15, 2020. The Company does not expect adoption of the new standard to have a material impact on its Condensed Consolidated Financial Statements.
Revenue from Contracts with Customers and Associated Balances	Revenue from Contracts with Customers and Associated Balances Nature of Products and Services Licenses for on-premises software provide the customer with a right to use the software as it exists when made available to the customer. Customers may purchase perpetual licenses or subscribe to licenses, which provide customers with the same functionality and differ mainly in the duration over which the customer benefits from the software. Revenue from distinct on-premises licenses is recognized upfront at the point in time when the software is made available to the customer. Revenue allocated to software maintenance and support services is recognized ratably over the contractual support period. Hardware products consist primarily of servers and associated components and function independently of the software products and as such are accounted for as separate performance obligations. Revenue allocated to hardware maintenance and support services is recognized ratably over the contractual support period. Professional services are primarily related to software implementation services and associated revenue is recognized upon customer acceptance. Contract Balances Timing of revenue recognition may differ from the timing of invoicing to customers. The Company records a contract asset or receivable when revenue is recognized prior to invoicing, or unearned revenue when revenue is recognized subsequent to invoicing. For perpetual licenses with multi-year product maintenance agreements, the Company generally invoices customers at the beginning of the coverage period. For multi-year subscription licenses, the Company generally invoices customers annually at the beginning of each annual coverage period. The Company records a contract asset related to revenue recognized for multi-year on-premises licenses as its right to payment is conditioned upon providing product support and services in future years. Significant Judgments The Company’s contracts with customers often include promises to transfer multiple products and services to a customer. Determining whether products and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment. Judgment is required to determine the standalone selling price (“SSP”) for each distinct performance obligation. For products and services aside from maintenance and support, the Company estimates SSP by adjusting the list price by historical discount percentages. SSP for software and hardware maintenance and support fees is based on the stated percentages of the fees charged for the respective products. The Company’s perpetual and term software licenses have significant standalone functionality and therefore revenue allocated to these performance obligations are recognized at a point in time upon electronic delivery of the download link and the license keys. Product maintenance and support services are satisfied over time as they are stand-ready obligations throughout the support period. As a result, revenues associated with maintenance services are deferred and recognized as revenue ratably over the term of the contract. Revenues associated with professional services are recognized at a point in time upon customer acceptance. Disaggregation of Revenue Please refer to the condensed consolidated statements of operations and note 16, segment reporting and concentrations, for discussion on revenue disaggregation by product type and by geography. The Company believes this level of disaggregation sufficiently depicts how the nature, amount, timing and uncertainty of our revenue and cash flows are affected by economic factors. Assets Recognized from Costs to Obtain a Contract with a Customer The Company recognizes an asset for the incremental costs of obtaining a contract with a customer if it expects the benefit of those costs to be longer than one year. The Company has determined that its sales commission program meets the requirements for cost capitalization. Total capitalized costs to obtain a contract were immaterial during the periods presented and are included in other current and long-term assets on our consolidated balance sheets. The Company applies a practical expedient to expense costs as incurred for costs to obtain a contract with a customer when the amortization period would have been one year or less.
Leases	Leases We have entered into operating leases for our various facilities. We determine if an arrangement is a lease at inception. Operating leases are included in ROU assets, and lease liability obligations in our condensed consolidated balance sheets. ROU assets represent our right to use an underlying asset for the lease term and lease liability obligations represent our obligation to make lease payments arising from the lease. ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. We have lease agreements with lease and non-lease components and account for such components as a single lease component. As most of our leases do not provide an implicit rate, we estimated our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. We use the implicit rate when readily determinable. The ROU asset also includes any lease payments made and excludes lease incentives and lease direct costs. Our lease terms may include options to extend or terminate the lease. Such extended terms have been considered in determining the ROU assets and lease liability obligations when it is reasonably certain that we will exercise that option. Lease expense is recognized on a straight-line basis over the lease term.