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Assumed, Restricted Cash Amount awarded to plaintiff Loss Contingency, Damages Awarded, Value Business combination, consideration transferred Total Business Combination, Consideration Transferred Performance-based restricted stock awards and units Performance Based Restricted Stock [Member] Performance Based Restricted Stock [Member] Schedule of Business Combination, Intangible Asset, Acquired, Finite-Lived Business Combination, Intangible Asset, Acquired, Finite-Lived [Table Text Block] Restructuring and related costs Restructuring and related costs Restructuring Costs Entity Emerging Growth Company Entity Emerging Growth Company Marketing Marketing Expense 2029 Long-Term Debt, Maturity, Year Three ROU assets obtained in exchange for new lease obligations: Right Of Use Assets Obtained In Exchange For Lease Obligations [Abstract] Right Of Use Assets Obtained In Exchange For Lease Obligations [Abstract] 2027 Finance Lease, Liability, to be Paid, Year One Dividends declared (in dollars per share) Common Stock, Dividends, Per Share, Declared Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Operating leases Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Weighted-average remaining lease term in years Finance Lease, Weighted Average Remaining Lease Term Non-cash lease expense Non Cash Lease Expense Non Cash Lease Expense Outstanding at beginning of period (in shares) Outstanding at end of period (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number 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] Capitalized debt issuance costs Debt Issuance Costs, Net Level 2 Fair Value, Inputs, Level 2 [Member] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Business Combination [Domain] Business Combination [Domain] Operating lease obligations Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract] Acquired in-place leases Leases, Acquired-in-Place [Member] LoopNet LoopNet [Member] LoopNet Less: imputed interest Finance Lease, Liability, Undiscounted Excess Amount Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Credit loss expense Accounts Receivable, Credit Loss Expense (Reversal) Plan Name [Axis] Plan Name [Axis] Operating lease costs: Operating Lease Cost [Abstract] Operating Lease Cost PEO PEO [Member] Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Proceeds from sale and settlement of investments and other assets Proceeds from Sale, Maturity and Collection of Investments Purchases of property, equipment, and other assets Payments to Acquire Property and Equipment and Other Assets Payments to Acquire Property and Equipment and Other Assets Income taxes payable Accrued Income Taxes, Current Changes in operating assets and liabilities, net of acquisitions: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised 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] Schedule of Product Information [Table] Nature of Operation, Product Information, Concentration of Risk [Table] Expected volatility Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate Retained Earnings Retained Earnings [Member] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Long-term debt principal payments Maturities of 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Payments CoStar CoStar [Member] CoStar Suite [Member] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Total current liabilities Liabilities, Current Interest capitalized for construction in process Interest Costs Capitalized Adjustment Equity interest in acquiree, total Business Combination, Consideration Transferred and Preacquisition Equity Interest in Acquiree Remainder of 2026 Long-Term Debt, Maturity, Interest Payments, Remainder of Fiscal Year Long-Term Debt, Maturity, Interest Payments, Remainder of Fiscal Year Restricted stock grants (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Individual: Individual [Axis] Numerator: Earnings Per Share Reconciliation [Abstract] LEASES Lessee, Finance Leases [Text Block] Entity [Domain] Entity [Domain] Net cash used in investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued 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Reconciliation, Percent Entity Interactive Data Current Entity Interactive Data Current Weighted-Average Grant Date Fair Value per Share Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract] Total operating lease costs Operating Lease, Cost Plan Name [Domain] Plan Name [Domain] Transaction cost, expense Business Combination, Acquisition-Related Cost, Expense Weighted-average-period expected to recognize the unrecognized compensation cost (in years) Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Exercise of stock options (in shares) Exercised (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Aggregate intrinsic value of options exercisable at end of period Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value Long-Lived Assets, Intangible Assets and Goodwill Goodwill and Intangible Assets, Policy [Policy Text Block] SEGMENT REPORTING Segment Reporting Disclosure [Text Block] Schedule of Goodwill [Table] Goodwill [Table] Lease liabilities Increase (Decrease) In Lease Liability Increase (Decrease) In Lease Liability 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] Other assets and (liabilities), net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Assets And Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Assets And Liabilities Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Performance-Based RSUs - With Market And Performance Condition Performance-Based RSUs - With Market And Performance Condition [Member] Performance-Based RSUs - With Market And Performance Condition Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Accrued capital expenditures and non-cash landlord incentives Capital Expenditures Incurred But Not Yet Paid And Noncash Landlord Incentives Capital Expenditures Incurred But Not Yet Paid And Noncash Landlord Incentives 2028 Finance Lease, Liability, to be Paid, Year Two Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Leases Lessee, Leases [Policy Text Block] Customer base amortization Amortization expense Amortization of Intangible Assets Fair value of rollover awards Business Acquisition, Replacement Equity Awards, Fair Value Business Acquisition, Replacement Equity Awards, Fair Value Deferred income taxes, net Deferred Income Tax Assets, Net Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Depreciation and amortization Depreciation, Depletion and Amortization Revenue recognized in the current period from the amounts in the beginning balance Contract with Customer, Liability, Prior Period Amounts Recognized Contract with Customer, Liability, Prior Period Amounts Recognized Entity Central Index Key Entity Central Index Key PEO Name PEO Name Schedule of Maturities of Long-term Debt Schedule of Maturities of Long-Term Debt [Table Text Block] 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 Schedule of Components of Other (Expense) Income Property, Plant, and Equipment, Lessor Asset under Operating Lease [Table Text Block] Depreciation and amortization expense Depreciation And Amortization, Lessor Asset Under Operating Lease Depreciation And Amortization, Lessor Asset Under Operating Lease Present value of lease liabilities Finance Lease, Liability Arrangement Duration Trading Arrangement Duration Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Current portion Contract with Customer, Liability, Current Segments [Axis] Segments [Axis] Prepaid expenses, other current assets and other assets Increase (Decrease) in Prepaid Expense and Other Assets Schedule of Supplemental Balance Sheet Information Related to Leases Supplemental Balance Sheet Information Related to Leases [Table Text Block] Supplemental Balance Sheet Information Related to Leases [Table Text Block] 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] Accounts receivable Accounts Receivable, before Allowance for Credit Loss, Current Other operating activities, net Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item EMPLOYEE BENEFIT PLANS Share-Based Payment Arrangement [Text Block] Intangible assets Business Combination, Recognized Asset Acquired, Identifiable Intangible Asset, Excluding Goodwill Cash and cash equivalents Business Combination, Recognized Asset Acquired, Cash and Cash Equivalent ASSETS Assets [Abstract] Long-term debt, net Long-term debt, net Long-Term Debt, Excluding Current Maturities Credit Facility [Axis] Credit Facility [Axis] Proceeds from exercise of stock options and employee stock purchase plan Proceeds From Exercise Of Stock Options and ESPP The cash inflow associated with the amount received from holders exercising their stock options and participants of employee stock purchase plans. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately. Underlying Security Market Price Change Underlying Security Market Price Change, Percent Balance Sheet Location [Axis] Statement of Financial Position Location, Balance [Axis] Debt Instrument [Axis] Debt Instrument [Axis] Canceled (in dollars per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value INVESTMENTS AND FAIR VALUE MEASUREMENTS Fair Value Disclosures [Text Block] Business Combination [Line Items] Business Combination [Line Items] Credit Facility [Domain] Credit Facility [Domain] Finite-lived intangible assets, gross Finite-Lived Intangible Assets, Gross 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] Share-based compensation arrangement, award vesting rights (as a percent) Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage Entity Address, Address Line One Entity Address, Address Line One Thereafter Finance Lease, Liability, to be Paid, Due After Year Four Finance Lease, Liability, to be Paid, Due After Year Four Stock repurchases under stock repurchase programs Treasury Stock, Value, Acquired, Cost Method Treasury Stock, Value, Acquired, Cost Method Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Stated interest rate (as a percent) Debt Instrument, Interest Rate, Stated Percentage Less: Allowance for credit losses Accounts Receivable, Allowance for Credit Loss, Current Long-term lease liabilities Operating Lease, Liability, Noncurrent Management stock purchase plan (in shares) Share-Based Payment Arrangement, Shares Withheld for Tax Withholding Obligation Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Intangible Assets, Net (Excluding Goodwill) [Abstract] Intangible Assets, Net (Excluding Goodwill) [Abstract] Settlements and impairments Settlements and impairments Restructuring, Settlement and Impairment Provisions Fair Value as of Grant Date Award Grant Date Fair Value Entity Registrant Name Entity Registrant Name Fair value of NCI in Domain’s partially-owned subsidiaries Business Combination, Consideration Transferred, Fair Value Of Noncontrolling Interests Business Combination, Consideration Transferred, Fair Value Of Noncontrolling Interests Settlement of existing debt Business Combination, Consideration Transferred, Settlement Of Debt Business Combination, Consideration Transferred, Settlement Of Debt Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Available for sale investments Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed, Available For Sale Debt Securities Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed, Available For Sale 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