Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and reported amounts of revenue and expenses during the reporting periods covered by the condensed consolidated financial statements and accompanying notes. These judgments, estimates and assumptions are used for, but not limited to (i) valuation of the Company’s common stock and stock awards, (ii) fair value of acquired intangible assets and goodwill, (iii) fair value of contingent consideration arrangements in connection with business combinations, (iv) incremental borrowing rate used for the Company’s operating leases, (v) useful lives of long-lived assets, (vi) impairment of intangible assets and goodwill, (vii) allowance for Compass Concierge receivables and (viii) income taxes and certain deferred tax assets. The Company determines its estimates and judgments based on historical experience and on various other assumptions that it believes are reasonable under the circumstances. However, actual results could differ from these estimates and these differences may be material. Business Combinations Business combinations are accounted for under the acquisition method of accounting. This method requires, among other things, allocation of the fair value of purchase consideration to the tangible and intangible assets acquired and liabilities assumed at their estimated fair values on the acquisition date. The excess of the fair value of purchase consideration over the values of these identifiable assets and liabilities is recorded as goodwill. When determining the fair value of assets acquired and liabilities assumed, management makes estimates and assumptions, especially with respect to intangible assets. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. During the measurement period, not to exceed one year from the date of acquisition, the Company may record adjustments to the assets acquired and liabilities assumed, with a corresponding offset to goodwill if new information is obtained related to facts and circumstances that existed as of the acquisition date. After the measurement period, any subsequent adjustments are reflected in the condensed consolidated statements of operations. Acquisition costs, consisting primarily of third-party legal and consulting fees, are expensed as incurred. Stock-Based Compensation The Company measures compensation expense for all stock-based awards based on the estimated fair value of the awards on the date of grant. Compensation expense is generally recognized as expense on a straight-line basis over the service period based on the vesting requirements. The Company recognizes forfeitures as they occur. For stock options, which the Company issues to employees, affiliated agents and in certain cases in connection with business combinations, the Company generally estimates the fair value using the Black-Scholes option pricing model, which requires the input of subjective assumptions, including (1) the fair value of common stock, (2) the expected stock price volatility, (3) the expected term of the award, (4) the risk-free interest rate and (5) expected dividends. The Company also issues RSUs to employees, affiliated agents and in certain cases in connection with business combinations. In addition to the issuance of RSUs to agents as equity compensation for the provision of services, the Company offered RSUs to affiliated agents through its Agent Equity Program. The Agent Equity Program offered affiliated agents the ability to elect to have a portion of their commissions earned during a calendar year to be paid in the form of RSUs. RSUs issued in connection with the Agent Equity Program were granted at the beginning of the year following the calendar year in which the commissions were earned and are subject to the terms and conditions of the 2012 Stock Incentive Plan and the 2021 Equity Incentive Plan, as applicable. The Company discontinued the Agent Equity Program following the issuance of RSUs during the first quarter of 2023 related to the 2022 Agent Equity Program. The Company's RSUs granted prior to December 2020 generally vest based upon the satisfaction of both a service-based condition and a liquidity event-based condition. The service-based vesting condition for these awards is generally satisfied over four years. The liquidity event-based vesting condition was met on March 31, 2021, the effective date of the Company’s registration statement filed in connection with the IPO, with subsequent expense recognized using the accelerated attribution method. In December 2020, the Company began issuing RSUs that vest upon the satisfaction of only a service-based vesting condition that generally ranges from one to five years. The fair value of these RSUs is measured based on the fair value of the Company’s common stock on the grant date and will be recognized as expense on a straight-line basis as the required service-based vesting condition is satisfied. Any vested RSUs that require only a service-based vesting condition will convert to common stock following vesting and their prescribed delayed settlement periods. For RSUs granted in connection with the 2021 and 2022 Agent Equity Programs, the Company determined the value of the stock-based compensation expense at the time the underlying commission was earned and recognized the associated expense on a straight-line basis over the requisite service periods beginning on the closing date of the underlying real estate commission transactions. The stock-based compensation expense was recorded as a liability throughout the service periods and was reclassified to Additional paid-in capital at the end of the vesting period when the underlying RSUs were issued. On a limited basis, the Company has issued stock options and RSUs that contain service, performance and market-based vesting conditions. Such awards were valued using a Monte Carlo simulation and the underlying expense will be recognized as the associated vesting conditions are met. New Accounting Pronouncements In March 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. An update was also issued expanding the scope of this guidance. The guidance provides optional expedients and exceptions for applying U.S. GAAP to contracts or other transactions affected by reference rate reform if certain criteria are met. The guidance was issued on March 12, 2020 and may be applied prospectively through December 31, 2022. On December 21, 2022, the FASB issued ASU 2022-06, Reference Rate Reform (Topic 848) - Deferral of the Sunset Date of Topic 848, which deferred the sunset date of Topic 848 from December 31, 2022 to December 31, 2024. The Company is evaluating applicable contracts and transactions to determine whether to elect the optional guidance. The adoption of this standard is not expected to have a material impact on the Company’s consolidated financial statements. In October 2021, the FASB issued ASU 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. The guidance amends ASC 805 to require acquiring entities to apply Topic 606 to recognize and measure contract assets and contract liabilities in a business combination. The amendment is effective for public companies with fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The amendment should be applied prospectively to business combinations occurring on or after the effective date. The Company adopted this standard as of January 1, 2023, and the adoption did not have a material impact on the Company’s consolidated financial statements. In March 2022, the FASB issued ASU 2022-02, Financial Instruments - Credit Losses (Topic 326) - Troubled Debt Restructurings and Vintage Disclosures, which requires enhanced disclosure of certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty while eliminating certain current recognition and measurement accounting guidance. This guidance also requires the disclosure of current-period gross write-offs by year of origination for financing receivables and net investments in leases. The amendments in this guidance are effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company adopted this standard as of January 1, 2023, and the adoption did not have a material impact on the Company’s consolidated financial statements.