Nature of Business (Policies)	3 Months Ended
Nature of Business (Policies)	Dec. 31, 2015
Accounting Policies [Abstract]
Fair Isaac Corporation	Fair Isaac Corporation Incorporated under the laws of the State of Delaware, Fair Isaac Corporation (“FICO”) is a provider of analytic, software and data management products and services that enable businesses to automate, improve and connect decisions. FICO provides a range of analytical solutions, credit scoring and credit account management products and services to banks, credit reporting agencies, credit card processing agencies, insurers, retailers, telecommunications providers, pharmaceutical companies, healthcare organizations, public agencies and organizations in other industries. In these condensed consolidated financial statements, Fair Isaac Corporation is referred to as “FICO,” “we,” “us,” “our,” or “the Company.”
Principles of Consolidation and Basis of Presentation	Principles of Consolidation and Basis of Presentation We have prepared the accompanying unaudited interim condensed consolidated financial statements in accordance with the instructions to Form 10-Q and the applicable accounting guidance. Consequently, we have not necessarily included in this Form 10-Q all information and footnotes required for audited financial statements. In our opinion, the accompanying unaudited interim condensed consolidated financial statements in this Form 10-Q reflect all adjustments (consisting only of normal recurring adjustments, except as otherwise indicated) necessary for a fair presentation of our financial position and results of operations. These unaudited condensed consolidated financial statements and notes thereto should be read in conjunction with our audited consolidated financial statements and notes thereto presented in our Annual Report on Form 10-K for the year ended September 30, 2015. The interim financial information contained in this report is not necessarily indicative of the results to be expected for any other interim period or for the entire fiscal year. The condensed consolidated financial statements include the accounts of FICO and its subsidiaries. All intercompany accounts and transactions have been eliminated.
Use of Estimates	Use of Estimates We make estimates and assumptions that affect the amounts reported in the financial statements and the disclosures made in the accompanying notes. For example, we use estimates in determining the collectibility of accounts receivable; the appropriate levels of various accruals; labor hours in connection with fixed-fee service contracts; the amount of our tax provision and the realizability of deferred tax assets. We also use estimates in determining the remaining economic lives and carrying values of acquired intangible assets, property and equipment, and other long-lived assets. In addition, we use assumptions to estimate the fair value of reporting units and share-based compensation. Actual results may differ from our estimates.
New Accounting Pronouncements Recently Issued or Adopted	New Accounting Pronouncements Recently Issued or Adopted In November 2015, the Financial Accounting Standards Board (“FASB”) issued ASU 2015-17, “Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes” (“ASU 2015-17”). ASU 2015-17 simplifies the presentation of deferred income taxes and requires that deferred tax liabilities and assets be classified as noncurrent in a classified statement of financial position. ASU 2015-17 applies to all entities that present a classified statement of financial position. ASU 2015-17 may be applied either prospectively to all deferred tax liabilities and assets or retrospectively to all periods presented. ASU 2015-17 is effective for fiscal years and interim periods within those fiscal years beginning after December 15, 2016, which means it will be effective for our fiscal year beginning October 1, 2017. Early adoption is permitted. We do not believe that adoption of ASU 2015-17 will have a significant impact on our consolidated financial statements. In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”). ASU 2014-09 requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 will replace most existing revenue recognition guidance in U.S. Generally Accepted Accounting Principles when it becomes effective and permits the use of either the retrospective or cumulative effect transition method. The guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. In August 2015, the FASB issued ASU No. 2015-14, “Deferral of the Effective Date” (“ASU 2015-14”), which defers the effective date for ASU 2014-09 by one year. For public entities, the guidance in ASU 2014-09 will be effective for annual reporting periods beginning after December 15, 2017 (including interim reporting periods within those periods), which means it will be effective for our fiscal year beginning October 1, 2018. Early adoption is permitted to the original effective date of December 15, 2016 (including interim reporting periods within those periods). We have not yet selected a transition method and we are currently evaluating the impact that the updated standard will have on our consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, “Simplifying the Presentation of Debt Issuance” (“ASU 2015-03”), which changes the presentation of debt issuance costs in financial statements. Under ASU 2015-03, an entity presents such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs is reported as interest expense. ASU 2015-03 is effective for fiscal years and interim periods within those fiscal years, beginning after December 15, 2015, which means it will be effective for our fiscal year beginning October 1, 2016. Early adoption is permitted. We do not believe that adoption of ASU 2015-03 will have a significant impact on our consolidated financial statements.