Statistical Measurement [Domain] Statistical Measurement [Domain] Schedule of Outstanding Foreign Currency Forward Contracts Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Award Timing Predetermined Award Timing Predetermined [Flag] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Entity File Number Entity File Number Additional Paid-in-Capital Additional Paid-in Capital [Member] Tabular List, Table Tabular List [Table Text Block] Earnings per share: Earnings Per Share, Basic [Abstract] Unbilled Unbilled Contracts Receivable New Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Accounts payable Increase (Decrease) in Accounts Payable Goodwill [Line Items] Goodwill [Line Items] Position [Axis] Position [Axis] Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Fed Funds Effective Rate Fed Funds Effective Rate Overnight Index Swap Rate [Member] Basic (in dollars per share) Earnings Per Share, Basic Adjustment to Compensation: Adjustment to Compensation [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Revenue from Contracts with Customers Revenue from Contract with Customer [Text Block] Software Software [Member] Software Schedule of Segment Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Foreign Exchange Contracts To Purchase Currencies Domain Foreign Exchange Contracts To Purchase Currencies [Domain] Foreign Exchange Contracts To Purchase Currencies Domain Revenue, remaining performance obligation, amount Revenue, Remaining Performance Obligation, Amount Adjustment to Compensation, Amount Adjustment to Compensation Amount Percentage Concentration Risk, Percentage Scores Scores [Member] Scores [Member] Percentage of performance obligation to be recognized Revenue, Remaining Performance Obligation, Percentage Share-based compensation Unallocated share-based compensation expense Share-Based Payment Arrangement, Noncash Expense Contract Amount Derivative Asset, Notional Amount Employee Stock Option Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] The 2018 Senior Notes Senior Notes May Twenty Eighteen [Member] Senior Notes May Twenty Eighteen [Member] Total stockholders’ deficit Beginning balance Ending balance Equity, Attributable to Parent Insider Trading Policies and Procedures [Line Items] Schedule of Composition of Property and Equipment Property, Plant and Equipment [Table Text Block] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Segment revenues: Segment Reporting Information, Revenue for Reportable Segment [Abstract] Hedging Designation [Domain] Hedging Designation [Domain] Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Current assets: Assets, Current [Abstract] Total liabilities and stockholders’ deficit Liabilities and Equity Interest rate of borrowings outstanding Line of Credit Facility, Interest Rate at Period End Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Liabilities and Stockholders’ Deficit Liabilities and Equity [Abstract] Cover [Abstract] Cover [Abstract] Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Maximum Maximum [Member] Accounting Policies [Abstract] Accounting Policies [Abstract] Unrecognized tax benefits, accrued interest Unrecognized Tax Benefits, Interest on Income Taxes Accrued Concentration Risk Type [Domain] Concentration Risk Type [Domain] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Debt Instrument [Line Items] Debt Instrument [Line Items] Treasury Stock Treasury Stock, Common [Member] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Senior Notes December 2021 Senior Notes December 2021 [Member] Senior Notes December 2021 Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] TransUnion, Equifax and Experian customers TransUnion, Equifax and Experian customers [Member] TransUnion, Equifax and Experian customers Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Schedule of Carrying Values and Estimated Fair Values of Debt Instruments Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] Other liabilities Other Liabilities, Noncurrent Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Deferred revenue Increase (Decrease) in Deferred Revenue Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Operating Segments Operating Segments [Member] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Current maturities on debt Current maturities on debt Long-Term Debt, Current Maturities Company Selected Measure Amount Company Selected Measure Amount Cash deposits Cash Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Name Measure Name Number of countries software is used (more than) Number of Countries in which Entity Operates Internal-use software Software and Software Development Costs [Member] Document Fiscal Period Focus Document Fiscal Period Focus Award Timing Method Award Timing Method [Text Block] Award Type Award Type [Axis] Deferred revenue, long-term portion Contract with Customer, Liability, Noncurrent Total debt Long-Term Debt Total assets Assets Cash flows from investing activities: Cash Provided by (Used in) Investing Activity, Continuing Operation [Abstract] Trading Symbol Trading Symbol Geographical [Domain] Geographical [Domain] Issuance of treasury stock under employee stock plans (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Entity Address, City or Town Entity Address, City or Town Net loss on marketable securities Marketable Security, Gain (Loss) Effect of exchange rate changes on cash Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Concentration Risk Type [Axis] Concentration Risk Type [Axis] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Assets: Assets, Fair Value Disclosure [Abstract] Emerging Growth Company Entity Emerging Growth Company William Lansing, Common Stock Subject to Vesting Trading Arrangement [Member] William Lansing, Common Stock Subject to Vesting Trading Arrangement Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Billed Billed Contracts Receivable Payments on revolving line of credit and term loans Repayments of Lines of Credit Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Provision for (benefit from) doubtful accounts Accounts Receivable, Credit Loss Expense (Reversal) PEO PEO [Member] Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Supplemental disclosures of non-cash investing and financing activities: Noncash Investing and Financing Items [Abstract] Proceeds from issuance of senior notes Proceeds from Issuance of Senior Long-Term Debt United States UNITED STATES Changes in operating assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Equifax Equifax [Member] Equifax Retained Earnings Retained Earnings [Member] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income Statement [Abstract] Income Statement [Abstract] Provision for income taxes Income Tax Expense (Benefit) Debt instrument basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Purchases of marketable securities Payments to Acquire Marketable Securities Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Product and Service [Domain] Product and Service [Domain] Customer Concentration Risk Customer Concentration Risk [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Property and equipment Property, Plant and Equipment, Gross Less: debt issuance costs Debt Issuance Costs, Current, Net Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Non-cash operating lease costs Operating Lease, Right-of-Use Asset, Periodic Reduction Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] SaaS software SaaS Products [Member] SaaS (Software as a service) Products City Area Code City Area Code Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Other accrued liabilities Total Accrued Liabilities, Current Capitalized internal-use software costs Payments to Develop Software Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Schedule of Rollforward of Deferred Revenues Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] William Lansing [Member] William Lansing Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Goodwill Balance at September 30, 2025 Balance at March 31, 2026 Goodwill Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount Total depreciation and amortization Depreciation Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Numerator for diluted and basic earnings per share: Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Equity Components [Axis] Equity Components [Axis] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Professional services Technology Service [Member] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Number of reportable segments Number of Reportable Segments Supplemental disclosures of cash flow information: Supplemental Cash Flow Information [Abstract] Disaggregation of Revenue [Line Items] Revenue from External Customer [Line Items] Accumulated goodwill impairment loss Goodwill, Impaired, Accumulated Impairment Loss Other Performance Measure, Amount Other Performance Measure, Amount Payments on debt issuance costs Payments of Debt Issuance Costs Entity Address, State or Province Entity Address, State or Province Payments on finance leases Finance Lease, Principal Payments Total current liabilities Liabilities, Current Credit facility restrictive covenant, maximum consolidated leverage ratio step up Leverage Ratios, Step Up, Maximum Leverage Ratios, Step Up, Maximum Income tax refunds Proceeds from Income Tax Refunds Derivative Instrument [Axis] Derivative Instrument [Axis] Individual: Individual [Axis] Additional paid-in-capital Additional Paid in Capital, Common Stock Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Revenue, remaining performance obligation, expected timing of satisfaction, period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] On-premises software On-Premises Products [Member] On-Premises Products[Member] Cash paid for interest Interest Paid, Excluding Capitalized Interest, Operating Activity Document Fiscal Year Focus Document Fiscal Year Focus Principles of Consolidation and Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Operating lease right-of-use assets Operating Lease, Right-of-Use Asset Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Entity Interactive Data Current Entity Interactive Data Current SOFR Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] Cash flows from operating activities: Cash Provided by (Used in) Operating Activity, Continuing Operation [Abstract] Current maturities on debt: Long-Term Debt, Current Maturities [Abstract] Contingencies Legal Matters and Contingencies [Text Block] Face Value Senior Notes Contract with customer, payment term Contract With Customer, Payment Term Contract With Customer, Payment Term Segment Information Segment Reporting Disclosure [Text Block] Goodwill [Table] Goodwill [Table] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Axis] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Marketable securities Marketable Securities, Noncurrent Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Business-to-business Scores Business to business Scores [Member] Business to business Scores Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Selling, general and administrative Selling, General and Administrative Expense Deferred income taxes Deferred Income Tax Assets, Net Depreciation and amortization Depreciation, Depletion and Amortization Other assets Other Assets, Noncurrent Customer [Domain] Customer [Domain] Interest payable Interest Payable, Current Entity Central Index Key Entity Central Index Key PEO Name PEO Name Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Revolving Credit Facility Revolving Credit Facility [Member] Arrangement Duration Trading Arrangement Duration Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Deferred revenue, current portion Contract with Customer, Liability, Current Segments [Axis] Segments [Axis] Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Exercise Price Award Exercise Price Entity Filer Category Entity Filer Category Local Phone Number Local Phone Number Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Assets Assets [Abstract] Long-term debt Long-term debt Long-Term Debt, Excluding Current Maturities Credit Facility [Axis] Credit Facility [Axis] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Debt Instrument [Axis] Debt Instrument [Axis] Fair Value Measurements Fair Value Disclosures [Text Block] Credit Facility [Domain] Credit Facility [Domain] Stockholders’ deficit: Equity, Attributable to Parent [Abstract] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Entity Address, Address Line One Entity Address, Address Line One Repurchases of common stock Treasury Stock, Value, Acquired, Cost Method Research and development Research and Development Expense Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Debt instrument, stated percentage Debt Instrument, Interest Rate, Stated Percentage Operating lease liabilities Operating Lease, Liability, Noncurrent William Lansing, Common Stock Trading Arrangement [Member] William Lansing, Common Stock Trading Arrangement Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Americas Americas [Member] Fair Value as of Grant Date Award Grant Date Fair Value Net receivables Accounts Receivable, after Allowance for Credit Loss Entity Registrant Name Entity Registrant Name Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Total operating expenses Segment operating expense Costs and Expenses Document Quarterly Report Document Quarterly Report Total Assets, Fair Value Disclosure Fair Value Long-Term Debt, Fair Value Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] On-premises and SaaS software On-premises and SaaS software [Member] On-premises and SaaS software Schedule of Debt Schedule of Debt [Table Text Block] Property and equipment Machinery and Equipment [Member] Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Restatement Determination Date: Restatement Determination Date [Axis] Issuance of treasury stock under employee stock plans Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Non-PEO NEO Non-PEO NEO [Member] Accounts Receivable Accounts Receivable [Member] Position [Domain] Position [Domain] Name Trading Arrangement, Individual Name All Award Types Award Type [Domain] Goodwill Goodwill Disclosure [Text Block] Equity Awards Adjustments Equity Awards Adjustments [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Foreign Exchange Contracts To Purchase Singapore Dollars With US Dollars Foreign Exchange Contracts To Purchase Singapore Dollars With United States Dollars [Member] [Domain] Foreign Exchange Contracts To Purchase Singapore Dollars With United States Dollars [Member] [Domain] Compensation Amount Outstanding Recovery Compensation Amount Senior Notes issued in a private placement to a group of institutional investors Debt Instrument, Face Amount Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Revenue recognized that was included in the deferred revenues balance at the beginning of the period Contract with Customer, Liability, Revenue Recognized Accrued compensation and employee benefits Increase (Decrease) in Employee Related Liabilities MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Name Awards Close in Time to MNPI Disclosures, Individual Name Shares used in computing earnings per share: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Non-platform software Non-platform software [Member] Non-platform software Deferred Revenue Arrangement, by Type [Table] Deferred Revenue Arrangement, by Type [Table] Share-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Treasury stock, at cost (65,562 and 65,093 shares at March 31, 2026 and September 30, 2025, respectively) Treasury Stock, Value Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Foreign Exchange Contracts To Sell European Euro for US Dollar Foreign Exchange Contracts To Sell European Euro For United States Dollar [Member] Foreign Exchange Contracts To Sell European Euro For U S dollar [Member] Other comprehensive income (loss): Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax [Abstract] Foreign Exchange Contracts To Purchase British Pounds With US Dollars Foreign Exchange Contracts To Purchase British Pounds With United States Dollars [Member] Foreign Exchange Contracts To Purchase British Pounds With US Dollars [Member] Segments [Domain] Segments [Domain] Europe, Middle East and Africa EMEA [Member] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Two Customers Two Customers [Member] Two Customers Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Current maturities on debt, gross Long-Term Debt Current Maturities, Gross Long-Term Debt Current Maturities, Gross Minimum Minimum [Member] Less: accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Eva Manolis [Member] Eva Manolis Company Selected Measure Name Company Selected Measure Name Senior Notes Senior Notes [Member] Debt Debt Disclosure [Text Block] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Accounts payable Accounts Payable, Current Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] All Executive Categories All Executive Categories [Member] Payments on senior notes Repayments of Senior Debt Goodwill [Roll Forward] Goodwill [Roll Forward] Diluted (in shares) Diluted weighted-average shares (in shares) Weighted Average Number of Shares Outstanding, Diluted Commitments and contingencies Commitments and Contingencies Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Derivative [Table] Derivative [Table] Entity Small Business Entity Small Business Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Unsettled repurchases of common stock, inclusive of excise tax accrued, but not yet paid Noncash Unsettled Repurchase Of Common Stock Noncash Unsettled Repurchase Of Common Stock Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Document Transition Report Document Transition Report Preferred stock ($0.01 par value; 1,000 shares authorized; none issued and outstanding) Preferred Stock, Value, Outstanding Underlying Securities Award Underlying Securities Amount Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Income Taxes Income Tax Disclosure [Text Block] Composition of Certain Financial Statement Captions Supplemental Balance Sheet Disclosures [Text Block] Less: allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss Proceeds from revolving line of credit and term loans Proceeds from Lines of Credit Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Hedging Designation [Axis] Hedging Designation [Axis] Change In Contract With Customer Liability [Roll Forward] Change In Contract With Customer Liability [Roll Forward] Change In Contract With Customer Liability Document Type Document Type Earnings per Share Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Product and Service [Axis] Product and Service [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Revenue from Contract with Customer Benchmark Revenue from Contract with Customer Benchmark [Member] Total revenues Revenue from Contract with Customer, Excluding Assessed Tax All Individuals All Individuals [Member] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Software recognized at a point in time Transferred at Point in Time [Member] Name Forgone Recovery, Individual Name Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Proceeds from issuance of treasury stock under employee stock plans Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Foreign currency translation adjustment Goodwill, Foreign Currency Translation, Gain (Loss) Taxes paid related to net share settlement of equity awards Payment, Tax Withholding, Share-Based Payment Arrangement Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Current liabilities: Liabilities, Current [Abstract] Geographical [Axis] Geographical [Axis] Schedule of Losses on Derivative Financial Instruments Derivative Instruments, Gain (Loss) [Table Text Block] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Borrowings outstanding Long-Term Line of Credit Active Markets for Identical Instruments (Level 1) Fair Value, Inputs, Level 1 [Member] Beginning balance (in shares) Ending balance (in shares) Shares, Outstanding Deferred revenue Deferred Revenue, Current Asia Pacific Asia Pacific [Member] Diluted (in dollars per share) Earnings Per Share, Diluted Senior Notes December 2019 Senior Notes December Six 2019 [Member] Senior Notes December Six 2019 Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Accounts receivable, net Short-term receivables Accounts Receivable, after Allowance for Credit Loss, Current Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Title of 12(b) Security Title of 12(b) Security Treasury stock, shares (in shares) Treasury Stock, Common, Shares Earnings per share: Earnings Per Share [Abstract] Consolidation Items [Domain] Consolidation Items [Domain] The 2019 Senior Notes and the 2021 Senior Notes Senior Notes 2019 and 2021 [Member] Senior Notes 2019 and 2021 Cash paid for income taxes, net of refunds of $7,796 and $663 during the six-month periods ended March 31, 2026 and 2025, respectively Income Taxes Paid, Net Repurchases of common stock (in shares) Treasury Stock, Shares, Acquired Award Timing Disclosures [Line Items] Long-term debt, gross Long-Term Debt, Gross Accrued compensation and employee benefits Employee-related Liabilities, Current Property and equipment, net Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization Unsecured revolving line of credit Line of Credit Facility, Current Borrowing Capacity Schedule of Composition of Other Current Liabilities Other Current Liabilities [Table Text Block] Gains (losses) on foreign currency forward contracts Gain (Loss) on Derivative Instruments, Net, Pretax Net income Net income Net Income (Loss) Attributable to Parent Expiration Date Trading Arrangement Expiration Date The 2026 Senior Notes Senior Notes 2026 [Member] Senior Notes 2026 Other liabilities Increase (Decrease) in Other Operating Liabilities Other Other Accrued Liabilities, Current Timing of Transfer of Good or Service [Axis] Timing of Transfer of Good or Service [Axis] Total Property, Plant and Equipment, Net Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Geographic Concentration Risk Geographic Concentration Risk [Member] Repurchases of common stock, inclusive of excise tax Payments for Repurchase of Common Stock Adoption Date Trading Arrangement Adoption Date Platform software Platform software [Member] Platform software Base Rate Base Rate [Member] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Accounts receivable Increase (Decrease) in Accounts Receivable Three Customers Three Customers [Member] Three Customers Entity Current Reporting Status Entity Current Reporting Status Derivative [Line Items] Derivative [Line Items] Customer [Axis] Customer [Axis] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Cash flows from financing activities: Cash Provided by (Used in) Financing Activity, Continuing Operation [Abstract] Operating income Operating Income (Loss) Revolving line of credit Line of Credit [Member] Retained earnings Retained Earnings (Accumulated Deficit) Net (gain) loss on sales and abandonment of property and equipment Gain (Loss) on Disposition of Property Plant Equipment Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Executive Category: Executive Category [Axis] Foreign currency forward contracts Foreign Exchange Forward [Member] Software recognized over contract term Transferred over Time [Member] Increases due to billings, excluding amounts recognized as revenue during the period Contract With Customer, Liability, Excluding Revenue Recognized Deferred Revenue Increased from Customer Contracts due to cash received The 2025 Senior Notes Senior Notes 2025 [Member] Senior Notes 2025 Current Fiscal Year End Date Current Fiscal Year End Date Short-term forward contracts, average maturities at inception (less than) Maximum Remaining Maturity of Foreign Currency Derivatives Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Schedule of Accounts Receivable Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Other expense, net Unallocated other expense, net Other Nonoperating Income (Expense) Statement [Table] Statement [Table] Fair Value Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value Less: long-term receivables Accounts Receivable, after Allowance for Credit Loss, Noncurrent Deferred income taxes Deferred Income Tax Expense (Benefit) Adjustments to reconcile net income to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Deferred revenues, beginning balance Deferred revenues, ending balance Contract with Customer, Liability Variable Rate [Domain] Variable Rate [Domain] Proceeds from sales of marketable securities Proceeds from Sale and Maturity of Marketable Securities Timing of Transfer of Good or Service [Domain] Timing of Transfer of Good or Service [Domain] Nature of Business Business Description and Accounting Policies [Text Block] Unrecognized tax benefits, uncertain tax positions Unrecognized Tax Benefits Denominator — share: Weighted Average Number of Shares Outstanding, Diluted [Abstract] All Adjustments to Compensation All Adjustments to Compensation [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Amendment Flag Amendment Flag Credit facility restrictive covenant, maximum consolidated leverage ratio Leverage Ratios Maximum Leverage Ratios Maximum Termination Date Trading Arrangement Termination Date Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Less: debt issuance costs Debt Issuance Costs, Noncurrent, Net Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Measure: Measure [Axis] Long-term debt: Long-Term Debt, Excluding Current Maturities [Abstract] TransUnion TransUnion [Member] TransUnion Forward foreign currency contracts fair value Derivative, Fair Value, Net Long-Lived Tangible Asset [Domain] Long-Lived Tangible Asset [Domain] Schedule of Financial Assets Measured at Fair Value on a Recurring Basis Fair Value, Assets Measured on Recurring Basis [Table Text Block] Basic (in shares) Basic weighted-average shares (in shares) Weighted Average Number of Shares Outstanding, Basic Schedule of Reconciliation of Numerators and Denominators of Basic and Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Segment Reporting [Abstract] Segment Reporting [Abstract] Cost of revenues Cost of Revenue Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Entity Tax Identification Number Entity Tax Identification Number Operating expenses: Costs and Expenses [Abstract] Accounts receivable, gross Accounts Receivable, before Allowance for Credit Loss Experian Experian [Member] Experian Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Short Short [Member] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares issued (in shares) Common Stock, Shares, Issued Use of Estimates Use of Estimates, Policy [Policy Text Block] Business-to-consumer Scores Business to consumer Scores [Member] Business to consumer Scores Schedule of Goodwill Schedule of Goodwill [Table Text Block] Interest expense, net Unallocated interest expense, net Interest Expense, Nonoperating Trading Arrangement: Trading Arrangement [Axis] Fair Isaac Corporation Nature Of Operations Policy [Policy Text Block] Nature of Operations, Policy [Policy Text Block] Total Shareholder Return Amount Total Shareholder Return Amount Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Insider Trading Arrangements [Line Items] Unallocated Corporate Expenses Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Security Exchange Name Security Exchange Name Total liabilities Liabilities Product Concentration Risk Product Concentration Risk [Member] Purchase of property and equipment included in accounts payable Capital Expenditures Incurred but Not yet Paid Common stock ($0.01 par value; 200,000 shares authorized, 88,857 shares issued and 23,295 and 23,764 shares outstanding at March 31, 2026 and September 30, 2025, respectively) Common Stock, Value, Outstanding Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Scores Scores Products [Member] Scores Products [Member] Statement [Line Items] Statement [Line Items] Consolidation Items [Axis] Consolidation Items [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Variable Rate [Axis] Variable Rate [Axis] Foreign Exchange Contracts To Purchase Currencies Axis Foreign Exchange Contracts To Purchase Currencies [Axis] Foreign Exchange Contracts To Purchase Currencies Axis Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents Cash and Cash Equivalent Common Stock Common Stock [Member] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Increase (decrease) in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Effect of dilutive securities (in shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment