Compass (COMP) 10-Q 13 May 21 2021 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2021	May 10, 2021
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Registrant Name	Compass, Inc.
Entity Central Index Key	0001563190
Current Fiscal Year End Date	--12-31
Entity File Number	001-40291
Entity Tax Identification Number	30-0751604
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Trading Symbol	COMP
Security Exchange Name	NYSE
Title of 12(g) Security	Class A Common Stock, $0.00001 par value per share
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	90 Fifth Avenue, 3rd Floor
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10011
City Area Code	212
Local Phone Number	913-9058
Entity Common Stock, Shares Outstanding		393,973,089

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 329.6	$ 440.1
Accounts receivable, net of allowance of $8.4 and $8.1, respectively	58.3	54.8
Compass Concierge receivables, net of allowance of $16.9 and $17.2, respectively	48.3	49.5
Other current assets	66	54.9
Total current assets	502.2	599.3
Property and equipment, net	144.2	141.7
Operating lease right-of-use assets	436.6	426.6
Intangible assets, net	79.2	45.6
Goodwill	154.5	119.8
Other non-current assets	50.5	32.1
Total assets	1,367.2	1,365.1
Current liabilities
Accounts payable	39.9	36.6
Commissions payable	55.3	62
Accrued expenses and other current liabilities	128.2	106.8
Current lease liabilities	73.3	68.1
Concierge credit facility	10.2	8.4
Total current liabilities	306.9	281.9
Non-current lease liabilities	441.8	435.9
Other non-current liabilities	26.7	23.5
Total liabilities	775.4	741.3
Commitments and contingencies (Note 6)
Convertible preferred stock, $0.00001 par value, 237,047,550 and 246,430,170 shares authorized at March 31, 2021 and December 31, 2020, respectively; 221,127,100 and 237,047,550 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	1,419.1	1,486.7
Stockholders' Deficit
Common stock, $0.00001 par value, 1,371,373,770 and 700,754,910 shares authorized at March 31, 2021 and December 31, 2020, respectively; 146,102,070 and 125,221,900 shares issued at March 31, 2021 and December 31, 2020, respectively; 143,852,070 and 122,971,900 shares outstanding at March 31, 2021 and December 31, 2020, respectively	0
Additional paid-in capital	486	238
Accumulated deficit	(1,313.3)	(1,100.9)
Total stockholders' deficit	(827.3)	(862.9)
Total liabilities, convertible preferred stock and stockholders' deficit	$ 1,367.2	$ 1,365.1

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for credit loss on accounts receivable current	$ 8.4	$ 8.1
Allowance for credit loss on financing receivable current	$ 16.9	$ 17.2
Convertible preferred stock par or stated value per share	$ 0.00001	$ 0.00001
Convertible preferred stock shares authorized	237,047,550	246,430,170
Convertible preferred stock shares issued	221,127,100	237,047,550
Convertible preferred stock shares outstanding	221,127,100	237,047,550
Common stock par or stated value per share	$ 0.00001	$ 0.00001
Common stock shares authorized	1,371,373,770	700,754,910
Common stock shares issued	146,102,070	125,221,900
Common stock shares outstanding	143,852,070	122,971,900

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Revenue	$ 1,113.9	$ 619.9
Operating expenses
Commissions and other related expense	942.2	508.8
Sales and marketing	111.3	106.5
Operations and support	70	61.1
Research and development	96.6	38.8
General and administrative	92.9	26.5
Depreciation and amortization	13.5	12.4
Total operating expenses	1,326.5	754.1
Loss from operations	(212.6)	(134.2)
Investment income, net	0	1.5
Interest expense	(0.5)
Loss before income taxes	(213.1)	(132.7)
Benefit from income taxes	0.7	0
Net loss	$ (212.4)	$ (132.7)
Net loss per share attributable to common stockholders, basic and diluted	$ (1.67)	$ (1.22)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted	126,917,284	108,764,426

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Convertible Preferred Stock [member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]
Beginning balance at Dec. 31, 2019	$ (681.6)		$ 1,525.7		$ 143.4	$ 0.1	$ (825.1)
Beginning balance, shares at Dec. 31, 2019			246,365,350	109,294,060
Net loss	(132.7)						(132.7)
Cumulative change in accounting principle (ASU 2016-13)		$ (5.6)						$ (5.6)
Issuance of shares in connection with acquisition ,Shares				221,390
Issuance of Series G convertible preferred stock, net of issuance costs			$ 1
Issuance of Series G convertible preferred stock, net of issuance costs, Shares			64,820
Exercise of stock options	0.2				0.2
Exercise of stock options, Shares				202,460
Stock-based compensation	11.1				11.1
Ending balance at Mar. 31, 2020	(808.6)		$ 1,526.7		154.7	$ 0.1	(963.4)
Ending balance, shares at Mar. 31, 2020			246,430,170	109,717,910
Beginning balance at Dec. 31, 2020	(862.9)		$ 1,486.7		238		(1,100.9)
Beginning balance, shares at Dec. 31, 2020			237,047,550	122,971,900
Net loss	(212.4)						(212.4)
Issuance of shares in connection with acquisition	4.3				4.3
Issuance of shares in connection with acquisition ,Shares				249,230
Conversion of Series D convertible preferred stock	67.6		$ (67.6)		67.6
Conversion of Series D convertible preferred stock , Shares			(15,920,450)	15,920,450
Exercise of stock options	$ 9.9				9.9
Exercise of stock options, Shares	4,710,490			3,972,930
Early exercise of stock options				737,560
Vesting of early exercised of stock options	$ 1.2				1.2
Stock-based compensation	165				165
Ending balance at Mar. 31, 2021	$ (827.3)		$ 1,419.1		$ 486		$ (1,313.3)
Ending balance, shares at Mar. 31, 2021			221,127,100	143,852,070

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities
Net loss	$ (212.4)	$ (132.7)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	13.5	12.4
Stock-based compensation	167.5	11.1
Change in acquisition related contingent consideration	(3.2)	0.7
Bad debt expense	3	6.3
Amortization of debt issuance costs	0.3
Changes in operating assets and liabilities:
Accounts receivable	(2)	(8.1)
Compass Concierge receivables	(0.7)	(60.8)
Other current assets	(10.7)	3.8
Other non-current assets	(7.4)	(4.2)
Operating lease right-of-use assets and operating lease liabilities	1.1	11.8
Accounts payable	(3.9)	(5.4)
Commissions payable	(7.9)	1.5
Accrued expenses and other liabilities	15.5	(4.1)
Net cash used in operating activities	(47.3)	(167.7)
Investing Activities
Proceeds from sales and maturities of marketable securities	0	17.3
Capital expenditures	(10)	(9.3)
Payments for acquisitions, net of cash acquired	(59.2)	(0.3)
Net cash (used in) provided by investing activities	(69.2)	7.7
Financing Activities
Proceeds from issuance of convertible preferred stock, net of issuance costs	0	1
Proceeds from exercise and early exercise of stock options	14.4	0.2
Proceeds from drawdowns on Concierge credit facility	6.3
Repayments of drawdowns on Concierge credit facility	(4.5)
Payments of contingent consideration related to acquisitions	(6.3)
Payments of debt issuance costs for the Revolving Credit and Guaranty Agreement	(1.4)
Payments of deferred offering costs	(2.5)
Net cash provided by financing activities	6	1.2
Net decrease in cash and cash equivalents	(110.5)	(158.8)
Cash and cash equivalents at beginning of period	440.1	491.7
Cash and cash equivalents at end of period	329.6	$ 332.9
Supplemental disclosures of cash flow information:
Cash paid for interest	0.1
Supplemental non-cash information:
Property and equipment included in accounts payable	1.6
Accrued consideration related to acquisitions	13
Conversion of Series D convertible preferred stock	67.6
Accrued deferred offering costs	6.7
Common Class A [Member]
Supplemental non-cash information:
Issuance of common stock for acquisitions	$ 4.3

Business and Basis of Presentat

Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Basis of Presentation	1. Business and Basis of Presentation Description of the Business Compass, Inc. (the “Company”) was incorporated in Delaware on October 4, 2012 under the name Urban Compass, Inc. On January 8, 2021, the board of directors of the Company approved a change to the Company’s name from Urban Compass, Inc. to Compass, Inc. Compass provides an end-to-end platform that empowers its residential real estate agents to deliver exceptional service to seller and buyer clients. The Company’s platform includes an integrated suite of cloud-based software for customer relationship management, marketing, client service and other critical functionality, all custom-built for the real estate industry which enables the Company’s core brokerage services. The platform also uses proprietary data, analytics, AI, and machine learning to deliver high value recommendations and outcomes for Compass agents and their clients. The Company’s agents are independent contractors who affiliate their real estate licenses with Compass, operating their businesses on Compass’s platform and under the Compass brand. The Company generates revenue from clients through its agents by assisting home sellers and buyers in listing, marketing, selling and finding homes as well as through the provision of services adjacent to the transaction, like title and escrow services, which comprise a smaller portion of the Company’s revenue to date. The Company currently generates substantially all of its revenue from commissions paid by clients at the time that a home is transacted. Stock Split In March 2021, the Company’s board of directors and the stockholders of the Company approved a ten-for-one l the ten-for-one Initial Public Offering On April 6, 2021, the Company completed its Initial Public Offering (“IPO”) and the Company’s Class A common stock began trading on the New York Stock Exchange on April 1, 2021 under the symbol “COMP”. In connection with the IPO, the Company issued and sold 26,296,438 shares of its common stock at a public offering price of $18.00 per share. The condensed consolidated financial statements as of March 31, 2021 and for the period then-ended do not reflect the transaction since the IPO closed subsequent to the period end. The Company received aggregate proceeds of $449.7 million from the IPO, net of the underwriting discount and before offering costs of approximately $11.0 million. Offering costs, including the legal, accounting, printing and other IPO-related non-current paid-in paid-in-capital. On March 31, 2021, in connection with the effectiveness of the Company’s IPO registration statement, the Company recognized $148.5 million in stock-based compensation expense for (i) certain RSUs that contained both service-based and liquidity event-based vesting conditions as the liquidity event-based vesting condition was satisfied upon effectiveness of the registration statement and (ii) certain stock options and RSU awards with service, performance and market-based vesting conditions that include stock price targets to be met after the listing of the Company’s stock on a public exchange. Basis of Presentation The condensed consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The Company’s condensed consolidated financial statements were prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and include the assets, liabilities, revenues and expenses of all controlled subsidiaries. The condensed consolidated statements of operations include the results of entities acquired from the date of the acquisition. The unaudited interim condensed consolidated financial statements and related disclosures have been prepared by management on a basis consistent with the annual consolidated financial statements and, in the opinion of management, include all adjustments necessary for a fair presentation of the interim periods presented. The results for the three months ended March 31, 2021 are not necessarily indicative of the operating results expected for the year ending December 31, 2021 or any other future period. Certain information and notes normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted under the Securities and Exchange Commission’s rules and regulations. Accordingly, the unaudited condensed consolidated financial statements and notes included herein should be read in conjunction with the Company’s audited consolidated financial statements and notes for the year ended December 31, 2020, which are included in the Company’s IPO prospectus on Form S-1 filed

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of 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 consolidated financial statements and reported amounts of revenue and expenses during the reporting periods covered by the 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) contingent considerations 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. There are many uncertainties regarding the ongoing coronavirus (“COVID-19”) COVID-19 COVID-19 COVID-19 COVID-19 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 significant 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 and affiliated agents, 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 and affiliated agents. In addition to the issuance of RSUs to agents as equity compensation for the provision of services, beginning in 2020, the Company offers RSUs to affiliated agents through its Agent Equity Program. The Agent Equity Program offers 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 are 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’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, except for the RSUs associated with the 2020 Agent Equity Program which vested immediately on the date of issuance. The liquidity event-based vesting condition is satisfied on the occurrence of a qualifying event, generally defined as a change in control or the effective date of the registration statement for the Company’s IPO. Upon the satisfaction of both vesting conditions and any delayed settlement period, the Company will issue shares to the award holders from the pool of authorized but unissued common stock. 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 begin to be recognized as expense when both the required service-based vesting condition and the liquidity event-based vesting condition has been achieved using the accelerated attribution method. The liquidity event-based vesting requirement was met on March 31, 2021, the effective date of the Company’s registration statement, see Note 1—“Business and Basis of Presentation—Initial Public Offering .” Beginning in December 2020, the Company began issuing RSUs that vest upon the satisfaction of only a service-based vesting condition that is generally satisfied over four 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 to be granted in connection with the 2021 Agent Equity Program, the Company determines the value of the stock-based compensation expense at the time the underlying commission is earned and begins to recognize 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 is recorded as a liability and will be reclassified to additional paid-in On a limited basis, the Company has issued stock options and RSUs that contain service, performance and market-based vesting conditions that include stock price targets to be met after the listing of the Company’s stock on a public exchange. Such awards are valued using a Monte Carlo simulation and the underlying expense will be recognized as the associated vesting conditions are met. Deferred Offering Costs Deferred offering costs, consisting of legal, accounting and other fees and costs relating to the IPO, are capitalized and recorded on the condensed consolidated balance sheets. The deferred offering costs will be offset against the proceeds received upon the closing of the IPO. As of March 31, 2021 and December 31, 2020, $11.0 million and $1.8 million, respectively, of deferred offering costs were capitalized in Other non-current New Accounting Pronouncements In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes Income Taxes step-up In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting

Business Combinations

Business Combinations	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
Business Combinations	3. Business Combinations During the three months ended March 31, 2021, the Company completed several business acquisitions including the acquisition of 100% of the ownership interests in KVS Title, LLC, a title insurance and escrow settlement services company, and two smaller real estate brokerages. The purpose of these acquisitions was to expand the Company’s title and escrow offerings and existing brokerage business in key domestic markets. The Company has accounted for these transactions as business combinations . Total Consideration The total consideration for acquisitions completed during the three months ended March 31, 2021 comprised $72.2 million of cash, net of cash acquired, and up to $2.0 million of additional cash that may be paid contingent on certain earnings-based targets being met through 2023. During the three months ended March 31, 2021, $59.2 million in cash was paid in connection with these acquisitions, net of cash acquired, and an aggregate of $13.0 million will be paid subsequent to March 31, 2021. Future cash payments were recorded as Accrued expenses and other current liabilities in the condensed consolidated balance sheet. The fair value of the assets acquired and the liabilities assumed primarily resulted in the recognition of: broker relationships of $31.4 million; trademark intangible assets of $6.5 million; operating lease right-of-use non-current non-current The Company has recorded the preliminary purchase price allocation as of the acquisition dates and expects to finalize its analysis within the measurement period (up to one year from the acquisition date) of the respective transaction. Any adjustments during the measurement period would have a corresponding offset to goodwill. Upon conclusion of the measurement period or final determination of the values of assets acquired or liabilities assumed, any subsequent adjustments are recorded to the consolidated statements of operations. Pro forma revenue and earnings for 2021 acquisitions have not been presented because they are not material to the Company’s consolidated revenue and results of operations, either individually or in the aggregate. Contingent Consideration Contingent consideration represents obligations of the Company to transfer cash and common stock to the sellers of certain acquired entities in the event that certain targets and milestones are met. Changes in contingent consideration measured at fair value on a recurring basis were as follows (in millions): Three Months Ended 2021 2020 Opening balance $ 39.8 $ 16.4 Acquisitions 2.0 — Payments and issuances (10.6 ) — Fair value (gains) losses included in net loss (3.2 ) 0.7 Closing Balance $ 28.0 $ 17.1 Other Acquisition Related Compensation In connection with the Company’s acquisitions, certain amounts paid or to be paid to selling shareholders are subject to clawback and forfeiture dependent on certain employees and agents providing continued service to the Company. These retention-based payments are accounted for as compensation for future services and the Company recognizes the expenses over the service period. As of March 31, 2021, the Company expects to pay an additional $29.3 million in future compensation to such selling shareholders in connection with its acquisitions. For the three months ended March 31, 2021 and 2020, the Company recognized $4.2 million and $1.3 million, respectively, in compensation expense within Operations and support in the accompanying condensed consolidated statements of operations related to these arrangements.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	4. Fair Value of Financial Assets and Liabilities The Company’s cash and cash equivalents of $329.6 million and $440.1 million as of March 31, 2021 and December 31, 2020, respectively, are held in cash and money market funds which are classified as Level 1 within the fair value hierarchy because they are valued using quoted prices in active markets. These are the Company’s only Level 1 financial instruments. The Company does not hold any Level 2 financial instruments. The Company’s contingent consideration liabilities of $28.0 million and $39.8 million as of March 31, 2021 and December 31, 2020, respectively, are the Company’s only Level 3 financial instruments. See Note 3 – “Business Combinations” for changes in contingent consideration for the three months ended March 31, 2021 and 2020. The following table presents the balances of contingent consideration (in millions): March 31, 2021 December 31, Accrued expenses and other current liabilities $ 7.4 $ 19.1 Other non-current 20.6 20.7 Total contingent consideration $ 28.0 $ 39.8 There were no transfers of financial instruments between Level 1, Level 2 and Level 3 during the periods presented. Level 3 Financial Liabilities The Company’s Level 3 financial liabilities relate to acquisition-related contingent consideration arrangements. Contingent consideration represents obligations of the Company to transfer cash and common stock to the sellers of certain acquired entities in the event that certain targets and milestones are met. As of March 31, 2021, the undiscounted maximum payment under these arrangements was $85.5 million, which is expected to be paid over a period of up to five years. The Company estimated the fair value of the contingent consideration using a Monte Carlo simulation, which is based on significant inputs, primarily forecasted future results of the acquired businesses, not observable in the market, discount rates and earnings volatility measures. The changes in the fair value of Level 3 financial liabilities are included within Operations and support in the accompanying condensed consolidated statements of operations (see Note 3 – “Business Combinations”). The following tables present quantitative information regarding the significant unobservable inputs utilized by the Company in the fair value measurement of Level 3 liabilities, consisting of different contingent consideration agreements, measured at fair value on a recurring basis: March 31, December 31, Discount rate 0.0% - 2.0% 0.0% - 2.0% Weighted average discount rate 1.7% 1.3% Earnings volatility 0% - 20% 0% - 18% Weighted-average earnings volatility 9.3% 6.9%

Debt

Debt	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Debt	5. Debt Concierge Credit Facility In July 2020, the Company entered into a Revolving Credit and Security Agreement (the “Concierge Facility”) with Barclays Bank PLC, as administrative agent, and the several lenders party thereto. The Concierge Facility provides for a $75.0 million revolving credit facility and is solely used to finance, in part, the Company’s Compass Concierge Program. The Concierge Facility is secured primarily by the Concierge Receivables and cash of the Compass Concierge Program. Borrowings under the Concierge Facility accrue interest at rates equal to (i) the adjusted London interbank offered rate (“LIBOR”) plus a margin of 3.00%, which may be adjusted, or an alternate rate of interest upon the occurrence of certain changes in LIBOR. The Company is required to pay an annual commitment fee of 0.50% on a quarterly basis based on the unused portion of the Concierge Facility. The principal amount, if any, is payable in full in January 2022, unless earlier terminated or extended. The interest rate on the Concierge Facility was 3.22% as of March 31, 2021. As of March 31, 2021 and December 31, 2020, there were $10.2 million and $8.4 million, respectively, in borrowings outstanding under the Concierge Facility. The Company has the option to repay the borrowings under the Concierge Facility without premium or penalty prior to maturity. The Concierge Facility contains customary affirmative covenants, such as financial statement reporting requirements, as well as covenants that restrict its ability to, among other things, incur additional indebtedness, sell certain receivables, declare dividends or make certain distributions, and undergo a merger or consolidation or certain other transactions. Additionally, in the event that the Company fails to comply with certain financial covenants that require the Company to meet certain liquidity-based measures, the commitments under the Concierge Facility will automatically be reduced to zero and the Company will be required to repay any outstanding loans under the Concierge Facility. As of March 31, 2021, the Company was in compliance with the covenants under the Concierge Facility. The Company incurred debt issuance costs of $1.4 million in connection with the Concierge Facility, which are included in Other current assets and Other non-current Revolving Credit Facility In March 2021, the Company entered into a Revolving Credit and Guaranty Agreement (the “Revolving Credit Facility”) with several lenders and issuing banks and Barclays Bank PLC, as administrative agent and as collateral agent. The Revolving Credit Facility provides for a $350.0 million revolving credit facility, which may be increased by the greater of $250.0 million and 18.5% of the Company’s consolidated total assets, plus such additional amount so long as the Company’s total net leverage ratio does not exceed 4.50:1.00 on a pro forma basis as of the most recent test period, subject to the terms of the Revolving Credit Facility. The Revolving Credit Facility also includes a letter of credit sublimit which is the lesser of (i) $125.0 million and (ii) the aggregate unused amount of the revolving commitments then in effect under the Revolving Credit Facility. The Company’s obligations under the Revolving Credit Facility are guaranteed by certain of the Company’s subsidiaries and are secured by a first priority security interest in substantially all of the Company’s assets and the Company’s subsidiary guarantors. Borrowings under the Revolving Credit Facility bear interest, at the Company’s option, at either (i) a floating rate per annum equal to the base rate plus a margin of 0.50% or (ii) a floating rate per annum equal to the rate at which dollar deposits are offered in the London interbank market plus a margin of 1.50%. In the Revolving Credit Facility, the base rate is defined as the highest of (a) the prime rate as quoted by The Wall Street Journal, (b) the federal funds effective rate plus 0.50%, (c) the rate at which dollar deposits are offered in the London interbank market for a one-month The Company is also obligated to pay other customary fees for a credit facility of this size and type, including a commitment fee on a quarterly basis based on amounts committed but unused under the Revolving Credit Facility of 0.175% per annum and fees associated with letters of credit. The principal amount, if any, is payable in full in March 2026, unless earlier terminated or extended. The Company has the option to repay the Company’s borrowings, and to permanently reduce the loan commitments whole or in part, under the Revolving Credit Facility without premium or penalty prior to maturity. As of March 31, 2021, there were no borrowings outstanding under the Revolving Credit Facility. The Revolving Credit Facility contains customary representations, warranties, affirmative covenants, such as financial statement reporting requirements, negative covenants and financial covenants, applicable to the Company and to the Company’s restricted subsidiaries. The negative covenants include restrictions that, among other things, restrict the Company and the Company’s subsidiaries’ ability to incur liens and indebtedness, make certain investments, declare dividends, dispose of, transfer or sell assets, make stock repurchases and consummate certain other matters, all subject to certain exceptions. The financial covenants require that (a) the Company maintains liquidity of at least $150.0 million as of the last day of each fiscal quarter and each date of a credit extension and (b) the Company’s consolidated total revenue as of the last day of each fiscal quarter be equal to or greater than the specified amount corresponding to such period. In the Revolving Credit Facility, liquidity is defined as the aggregate of (i) revolving commitments under the Revolving Credit Facility minus the aggregate principal amount of all outstanding loans, any drawn and unreimbursed amounts under letters of credit and the maximum amount that may be drawn under letters of credit, plus (ii) unrestricted cash that is generally available for use by the Company and the Company’s subsidiaries. As of March 31, 2021, the Company was in compliance with the covenants under the Revolving Credit Facility. The Revolving Credit Facility includes customary events of default that include, among other things, nonpayment of principal, interest or fees, inaccuracy of representations and warranties, violation of certain covenants, cross default to certain other indebtedness, bankruptcy and insolvency events, material judgments, change of control and certain material ERISA events. The occurrence of an event of default could result in the acceleration of the obligations under the Revolving Credit Facility. The Company incurred debt issuance costs of $1.4 million in connection with the Revolving Credit Facility, which are included in Other current assets and Other non-current

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure [Text Block]	6. Commitments and Contingencies Legal Proceedings From time to time, the Company may be involved in disputes or regulatory inquiries that arise in the ordinary course of business. When the Company determines that a loss is both probable and reasonably estimable, a liability is recorded and disclosed if the amount is material to the Company’s business taken as a whole. When a material loss contingency is only reasonably possible, the Company does not record a liability, but instead discloses the nature and the amount of the claim and an estimate of the loss or range of loss, if such an estimate can reasonably be made. Legal costs related to the defense of loss contingencies are expensed as incurred. Claims or regulatory actions against the Company, whether meritorious or not, could have an adverse impact on the Company due to legal costs, diversion of management resources and other elements. Except as identified with respect to the matters below, the Company does not believe that the outcome of any individual existing legal or regulatory proceeding to which it is a party will have a material adverse effect on its results of operations, financial condition or overall business in each case, taken as a whole. Avi Dorfman v. Robert Reffkin and Urban Compass, Inc. In July 2014, Avi Dorfman (“Dorfman”) and RentJolt, Inc. (“RentJolt”) (collectively, “Plaintiffs”) filed suit against the Company and Robert Reffkin (“Defendants”), seeking compensation for certain services, trade secrets and other contributions allegedly provided in the formation of the Company. After miscellaneous motion practice, in June 2018, Defendants moved for summary judgment, the court held oral argument in October 2018 and ultimately denied the Defendants’ motion for summary judgment in October 2019. In November 2019, Defendants appealed portions of the court’s summary judgment ruling. In February 2020, the appellate court granted in part and denied in part Defendants’ appeal resulting in one plaintiff (RentJolt) voluntarily discontinuing its only remaining claim and leaving the case. Defendants have one motion in limine pending. A trial date has been set for September 2021. Realogy Holdings Corp., et al v. Urban Compass, Inc. and Compass Inc. In July 2019, Realogy Holdings Corp., NRT New York LLC (“Corcoran”) and many of its related entities (collectively, “Plaintiffs”) filed a complaint against the Company in the New York Supreme Court. The complaint alleges various violations of New York and California state law related to claims of unfair competition and seeks unspecified damages. The Company filed a Motion to Dismiss in September 2019. In September 2019, Plaintiffs filed an amended complaint, removing one claim and adding a claim for defamation. In November 2019, the Company moved to compel arbitration related to claims asserted by Corcoran and moved to dismiss all of the counts. In June 2020, the Court denied the motion to dismiss and denied the motion to compel arbitration as moot, granting Plaintiffs leave to amend the complaint as to claims asserted by Corcoran without prejudice to Defendants’ ability to move to compel or dismiss the Second Amended Complaint. On July 3, 2020, Plaintiffs filed their Second Amended Complaint. On December 18, 2020, the Court denied the Company’s motion to compel arbitration on Plaintiffs’ second amended complaint without prejudice. Defendants’ Answer to the Second Amended Complaint and Counterclaims were filed on January 28, 2021. Additionally, the Company filed its appeal of the lower Court’s denial of the Company’s motion to dismiss and motion to compel arbitration on February 1, 2021. The appeal has been fully briefed and is awaiting determination. Discovery is proceeding. The Company is unable to predict the outcome of this action or to reasonably estimate the possible loss or range of loss, if any, arising from the claims asserted therein. Letter of Credit Agreements The Company has irrevocable letters of credit with various financial institutions, primarily related to security deposits for leased facilities. As of March 31, 2021 and December 31, 2020, the Company was contingently liable for $51.7 million and $50.7 million, respectively, under these letters of credit. These letters of credit are collateralized by the Company’s cash and cash equivalents. Escrow and Trust Deposits As a service to its home buyers and home sellers, the Company administers escrow and trust deposits which represent undistributed amounts for the settlement of real estate transactions. The escrow and trust deposits totaled $238.7 million and $46.1 million, respectively as of March 31, 2021 and December 31, 2020. These deposits are not assets of the Company and therefore are excluded from the accompanying condensed consolidated balance sheets. However, the Company remains contingently liable for the disposition of these deposits.

Convertible Preferred Stock and

Convertible Preferred Stock and Common stock	3 Months Ended
	Mar. 31, 2021
Stockholders' Equity Note [Abstract]
Convertible Preferred Stock and Common stock	7. Convertible Preferred Stock and Common Stock Convertible Preferred Stock In March 2020, the Company issued an additional 64,820 shares of its Series G convertible preferred stock for proceeds of $1.0 million. In March 2021, the holders of 15,920,450 shares of the Company’s Series D convertible preferred stock elected to convert into an equal number of shares of Class A common stock. The Company’s convertible preferred stock authorized, issued and outstanding and the aggregate liquidation preferences, including dividends that would be due if and when declared by the board of directors are as follows (in millions, except share and per share amounts): March 31, 2021 Series of Convertible Preferred Stock Year Issued Shares Shares Issuance Price/ Price Aggregate Carrying Value Series A 2013 54,811,930 54,811,930 $ 1.0000 $ 54.8 $ 54.7 Series B 2014-2015 18,133,240 18,133,240 2.0766 37.7 37.5 Series C 2015-2016 13,580,260 13,580,260 4.0500 55.0 54.8 Series D 2016-2017 15,920,450 — 4.2632 — — Series E 2017-2018 78,543,890 78,543,890 6.7478 530.0 529.0 Series F 2018 33,686,160 33,686,160 11.8570 399.4 398.8 Series G 2019-2020 22,371,620 22,371,620 15.4269 345.1 344.3 237,047,550 221,127,100 $ 1,422.0 $ 1,419.1 During April 2021, all remaining shares of convertible preferred stock converted into 223,033,725 shares of Class A common stock. The rights, preferences, restrictions and privileges of the holders of convertible preferred stock are included in the Company’s IPO prospectus on Form S-1 filed Common Stock In February 2021, the Company approved the establishment of Class C common stock and an agreement with the Company’s CEO to exchange his Class A common stock for Class C common stock. On March 31, 2021, in connection with the effectiveness of the registration statement for the Company’s IPO, 15,244,490 shares of Class A common stock held by the Company’s founder and CEO were automatically exchanged for an equivalent number of shares of Class C common stock. In addition, any Class A common stock issued to the CEO from awards granted to him prior to February 2021 will also automatically be exchanged for Class C common stock. Each share of Class C common stock is entitled to twenty votes per share and will be convertible at any time into one share of Class A common stock and will automatically convert into Class A common stock under certain “sunset” provisions. Other than certain permitted transfers for estate planning purposes, upon a transfer of Class C common stock, the Class C common stock will convert into Class A common stock. As of March 31, 2021, the Company had three classes of common stock: Class A common stock, Class B common stock and Class C common stock. Each class has par value of $0.00001. March 31, 2021 Shares Shares Shares Class A common stock 1,000,754,910 126,295,420 124,045,420 Class B common stock 270,618,860 4,562,160 4,562,160 Class C common stock 100,000,000 15,244,490 15,244,490 Total 1,371,373,770 146,102,070 143,852,070 As of December 31, 2020, the Company had two classes of common stock: Class A common stock and Class B common stock. Each class has a par value of $0.00001. December 31, 2020 Shares Shares Shares Class A common stock 530,136,050 118,549,390 116,299,390 Class B common stock 170,618,860 6,672,510 6,672,510 Total 700,754,910 125,221,900 122,971,900 In April 2021, the Company adopted a restated certificate of incorporation and changed its authorized capital stock to consist of 12,500,000,000 shares of Class A common stock, 1,250,000,000 shares of Class B common stock, 100,000,000 shares of Class C common stock and 25,000,000 shares of undesignated preferred stock. Holders of Class A common stock are entitled to one vote per share. Holders of Class B common stock are not entitled to vote. Holders of Class C common stock are entitled to twenty votes per share. Each share of Class C common stock is convertible at any time of the option of the holder into one share of Class A common stock. Each share of Class C common stock will automatically convert into a share of Class A common stock upon sale or transfer, except for certain permitted transfers. A description of all other rights, preferences and privileges of the holders of the Company’s common stock are included in the Company’s IPO prospectus on Form S-1 filed As of March 31, 2021 and December 31, 2020, the Company had shares of common stock reserved for issuance as follows: March 31, December 31, Convertible preferred stock outstanding 223,033,725 238,954,050 Options issued and outstanding 59,603,390 62,827,150 Restricted stock units issued and outstanding 50,272,925 32,556,160 Shares available for future stock-based incentive award issuances 41,105,315 11,679,150 Total 374,015,355 346,016,510 As of March 31, 2021 and December 31, 2020, the Company had 2,250,000 shares of Class A common stock issued and held as treasury stock.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	8. Stock-Based Compensation 2012 Stock Incentive Plan In October 2012, the Company adopted the 2012 Stock Incentive Plan (the “2012 Plan”). Under the 2012 Plan, employees and non-employees ten-year 2021 Equity Incentive Plan In February 2021, the Company’s board of directors and stockholders adopted and approved the 2021 Equity Incentive Plan (the “2021 Plan”), with an initial pool of 29,666,480 shares of common stock available for granting stock-based awards plus any reserved shares of common stock not issued or subject to outstanding awards granted under the Company’s 2012 Plan. The 2021 Plan became effective on March 30, 2021 and as of that date, the Company ceased granting new awards under the 2012 Plan. As of March 31, 2021, there were 41,105,315 shares available for future grants under the 2021 Plan. 2021 Employee Stock Purchase Plan In February 2021, the board of directors and stockholders also adopted and approved the 2021 Employee Stock Purchase Plan (the “ESPP”). The ESPP authorizes the issuance of 7,416,620 shares of common stock to purchase rights granted to the Company’s employees or to employees of its designated affiliates. In addition, on January 1 of each year beginning in 2022 and continuing through 2031, the aggregate number of shares of common stock authorized for issuance under the ESPP shall be increased automatically by the number of shares equal to one percent (1%) of the total number of outstanding shares of common stock and shares of preferred stock of the Company outstanding (on an as converted to common stock basis) on the immediately preceding December 31 (rounded down to the nearest whole share), although the board of directors or one of its committees may reduce the amount of the increase in any particular year. No more than 150,000,000 shares of common stock may be issued over the term of the ESPP, subject to certain exceptions set forth in the ESPP. As of the date of this filing, no shares have been granted under the ESPP. Stock Options A summary of stock option activity under the 2012 Plan and the 2021 Plan, including 1,061,250 stock options that were granted outside of the 2012 Plan in 2019, is presented below (in millions, except share and per share amounts): Number of Weighted Weighted Average Aggregate Balances as of December 31, 2020 62,827,150 $ 4.55 7.8 $ 1,208.0 Granted 1,888,660 11.04 Exercised (4,710,490 ) 3.05 Forfeited (401,930 ) 6.35 Balances as of March 31, 2021 59,603,390 $ 4.86 7.7 $ 780.0 Exercisable and vested at March 31, 2021 32,491,554 $ 3.47 6.6 $ 470.6 During the three months ended March 31, 2021 and 2020, the intrinsic value of options exercised was $79.8 million and $0.5 million, respectively. Restricted Stock Units A summary of RSU activity under the 2012 Plan and the 2021 Plan is presented below: Number of Weighted Balances as of December 31, 2020 32,556,160 $ 6.75 Granted 18,088,710 12.61 Vested and converted to common stock — — Forfeited (371,945 ) 11.80 Balances as of March 31, 2021 50,272,925 $ 8.82 Included in the table above are 8,611,810 RSUs granted to an executive employee during the three months ended March 31, 2021. These RSUs have service, performance and market-based vesting conditions that include stock price targets to be met after the listing of the Company’s stock on a public exchange. Stock-Based Compensation Expense Total stock-based compensation expense included in the condensed consolidated statements of operations is as follows (in millions): Three Months Ended March 31, 2021 Three IPO Related Other Total March 31, Commissions and other related expense $ 41.7 $ 2.9 $ 44.6 $ 4.1 Sales and marketing 1.8 7.2 9.0 2.9 Operations and support 3.1 1.9 5.0 0.8 Research and development 46.9 2.6 49.5 0.5 General and administrative 55.0 4.4 59.4 2.8 Total stock-based compensation expense $ 148.5 $ 19.0 $ 167.5 $ 11.1 As more fully described in Note 1 – “Business and Basis of Presentation ”, As of March 31, 2021, unrecognized stock-based compensation expense totaled $451.5 million and is expected to be recognized over a weighted-average period of 3.4 years. The Company has not recognized any tax benefits from stock-based compensation as a result of the full valuation allowance maintained on its deferred tax assets. Early Exercise of Stock Options A majority of the stock options granted under the 2012 Plan provide option holders the right to elect to exercise unvested options in exchange for restricted common stock. Shares received from such early exercises are subject to repurchase in the event of the optionee’s termination of service until the stock options are fully vested at the lesser of the original issuance price or the fair value the Company’s common stock. During the three months ended March 31, 2021, 737,560 stock options were early exercised for total proceeds of $4.5 million. As of March 31, 2021, 1,740,600 shares of common stock received by holders from an early exercise were subject to repurchase. The cash proceeds received for unvested shares of common stock recorded within Accrued expenses and other current liabilities and Other non-current paid-in

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes The Company recognized a benefit from income taxes of $0.7 million for the three months ended March 31, 2021. This benefit resulted from a partial reduction in the valuation allowance related to the carryover tax basis in deferred tax liabilities from acquisitions. Additionally, the Company incurred current tax expense from its operations in India, which was fully offset by a deferred tax benefit for future AMT tax credits. No benefit from income taxes was recognized during the three months ended March 31, 2020. The Company continues to maintain a full valuation allowance on all domestic net deferred tax assets based on numerous factors including estimated future taxable income and historic profitability. The Company does not have any amount related to uncertain tax positions as of the period ended March 31, 2021 nor does it expect a substantial increase in the next 12 months. If applicable, the Company recognizes interest and penalties related to uncertain tax positions in the income tax provision. The United States is the Company’s only material tax jurisdiction and as a result of net operating loss carryforwards, the Company is subject to audit for all years for US federal tax purposes.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	10. Net Loss Per Share Attributable to Common Stockholders The Company computes net loss per share under the two-class The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in millions, except share and per share amounts): Three Months Ended March 31, 2021 2020 Numerator: Net loss attributable to common stockholders $ (212.4 ) $ (132.7 ) Denominator: Weighted-average number of shares outstanding used to compute net loss per share attributable to common stockholders, basic and diluted 126,917,284 108,764,426 Net loss per share attributable to common stockholders, basic and diluted $ (1.67 ) $ (1.22 ) The following participating securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented, because including them would have been anti-dilutive (on an as-converted Three Months Ended March 31, 2021 2020 Convertible preferred stock 223,033,725 248,336,668 Outstanding stock options 59,603,390 50,414,160 Outstanding RSUs 50,272,925 23,992,200 Unvested early exercised options 1,740,600 — Unvested common stock 525,930 9 83 Total 335,176,570 323,726,518

Compass Concierge Receivables a

Compass Concierge Receivables and Allowance for Credit Losses	3 Months Ended
	Mar. 31, 2021
Receivables [Abstract]
Compass Concierge Receivables and Allowance for Credit Losses	11. Compass Concierge Receivables and Allowance for Credit Losses In 2018, the Company launched the Compass Concierge Program for home sellers who have engaged Compass as their exclusive listing agent. The program, initially launched by the Company, is based on a services model (“Concierge Classic”) provided by Compass Concierge, LLC (“Compass Concierge”), which includes items such as consultation on suggested cosmetic updates or modifications to a specific property or guidance on securing licensed contractors or vendors to perform non-structural up-front In 2019, the Compass Concierge Program was expanded to include a loan program underwritten by an independent third-party lender (the “Lender”) through a commercial arrangement with Compass Concierge (“Concierge Capital”). Under the Concierge Capital program, the Lender originates and services unsecured consumer loans to home sellers following its independent underwriting process pursuant to program-level criteria provided by the Company. Pursuant to the Company’s agreement with the Lender, the consumer loans are unsecured, interest-free and have no associated fees except for late fees that the Lender may charge in its sole discretion. The Company has no right or obligation with respect to any individual consumer loan originated by the Lender. Under the agreement with the Lender, the Company has repayment rights against the Lender in connection with a corporate loan. Payment to the Company for these services under the Concierge Classic model or repayment of the loan funds under the Concierge Capital model is due upon the earlier of a successful home sale, the termination of the listing agreement, or one year from the date in which costs were originally funded. Compass Concierge receivables (“Concierge Receivables”) are stated at the amount advanced to the home sellers, net of an estimated allowance for credit losses (“ACL”). The Company does not recognize any revenue or earn any fees from the Compass Concierge Program. The Company incurs service fees payable to the Lender and incurs bad debt expense in connection with the Compass Concierge Program. The Company manages its credit risk by establishing a comprehensive credit policy for the approval of projects under the Concierge Classic program and new loans under the Concierge Capital program, while monitoring and reviewing the performance of its existing Concierge Receivables. Factors considered include but not limited to: • No negative liens or judgements on the property; • Seller’s available equity on the property; • Loan to listing price ratio; • FICO score (only for Concierge Capital program); and • Macroeconomic conditions. Credit Quality The Company monitors credit quality by evaluating various attributes and utilizes such information in its evaluation of the appropriateness of the ACL. Based on the Company’s experience, the key credit quality indicator is whether the underlying properties associated with the Concierge Receivables will be sold or not. Concierge Receivables associated with properties that are eventually sold have a lower credit risk than those that are associated with properties that are not sold. For Concierge Receivables where repayments have not been triggered (i.e., earlier of (i) sale of the property, (ii) termination of a listing agreement or (iii) 12 months from the date costs were originally funded), the Company establishes an estimate as to the percentage of underlying properties that will be sold based on historical data. This estimate is updated quarterly and on an annual basis. As of March 31, 2021 and December 31, 2020, the amount of outstanding Concierge Receivables related to unsold properties was approximately 95% and 93%, respectively. Allowance for credit losses The Company maintains an ACL for the expected credit losses over the contractual life of the Concierge Receivables. The amount of ACL is based on ongoing, quarterly assessments by management. Historical loss experience is generally the starting point when the Company estimates the expected credit losses. The Company then considers whether (i) current conditions, such as the impact of COVID-19 Three Months Beginning of period $ 17.2 Allowances 1.9 Net write-offs and other (2.2 ) End of period $ 16.9 Aging Status The Company generally considers Concierge Receivables to be past due after being outstanding for over 30 days after initial billing. Changes in the Company’s estimate to the ACL is recorded through bad debt expense as Sales and marketing expense in the condensed consolidated statements of operations and individual accounts are charged against the allowance when all reasonable collection efforts are exhausted. The following tables present the aging analysis of Concierge Receivables as of March 31, 2021 (in millions): 31-90 days Over 90 Total Past Current Total March 31, 2021 $ 8.1 $ 13.8 $ 21.9 $ 43.3 $ 65.2

Restructuring Activities and CO

Restructuring Activities and COVID-19 Update	3 Months Ended
	Mar. 31, 2021
Restructuring and Related Activities [Abstract]
Restructuring Activities and COVID-19 Update	12. Restructuring Activities and COVID-19 Beginning in March 2020, the onset of the COVID-19 shelter-in-place stay-at-home in-person COVID-19, COVID-19 stay-at-home stay-at-home The expenses resulting from these cost-saving measures were included in the consolidated statement of operations for the three months ended March 31, 2020, as follows (in millions): Three Months Ended March 31, 2020 Severance Lease Total Sales and marketing $ 1.5 $ 1.2 $ 2.7 Operations and support 2.8 — 2.8 Research and development 0.7 — 0.7 General and administrative 0.4 — 0.4 Total $ 5.4 $ 1.2 $ 6.6 The Company did not recognize any restructuring expenses during the three-months ended March 31, 2021. As of March 31, 2021 and December 31, 2020, the Company did not have any material remaining liabilities related to restructuring costs.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Events Business Combinations In May 2021 ,

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The Company’s condensed consolidated financial statements were prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and include the assets, liabilities, revenues and expenses of all controlled subsidiaries. The condensed consolidated statements of operations include the results of entities acquired from the date of the acquisition. The unaudited interim condensed consolidated financial statements and related disclosures have been prepared by management on a basis consistent with the annual consolidated financial statements and, in the opinion of management, include all adjustments necessary for a fair presentation of the interim periods presented. The results for the three months ended March 31, 2021 are not necessarily indicative of the operating results expected for the year ending December 31, 2021 or any other future period. Certain information and notes normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted under the Securities and Exchange Commission’s rules and regulations. Accordingly, the unaudited condensed consolidated financial statements and notes included herein should be read in conjunction with the Company’s audited consolidated financial statements and notes for the year ended December 31, 2020, which are included in the Company’s IPO prospectus on Form S-1 filed
Use of Estimates	Use of Estimates The preparation of 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 consolidated financial statements and reported amounts of revenue and expenses during the reporting periods covered by the 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) contingent considerations 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. There are many uncertainties regarding the ongoing coronavirus (“COVID-19”) COVID-19 COVID-19 COVID-19 COVID-19
Business Combinations	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 significant 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	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 and affiliated agents, 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 and affiliated agents. In addition to the issuance of RSUs to agents as equity compensation for the provision of services, beginning in 2020, the Company offers RSUs to affiliated agents through its Agent Equity Program. The Agent Equity Program offers 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 are 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’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, except for the RSUs associated with the 2020 Agent Equity Program which vested immediately on the date of issuance. The liquidity event-based vesting condition is satisfied on the occurrence of a qualifying event, generally defined as a change in control or the effective date of the registration statement for the Company’s IPO. Upon the satisfaction of both vesting conditions and any delayed settlement period, the Company will issue shares to the award holders from the pool of authorized but unissued common stock. 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 begin to be recognized as expense when both the required service-based vesting condition and the liquidity event-based vesting condition has been achieved using the accelerated attribution method. The liquidity event-based vesting requirement was met on March 31, 2021, the effective date of the Company’s registration statement, see Note 1—“Business and Basis of Presentation—Initial Public Offering .” Beginning in December 2020, the Company began issuing RSUs that vest upon the satisfaction of only a service-based vesting condition that is generally satisfied over four 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 to be granted in connection with the 2021 Agent Equity Program, the Company determines the value of the stock-based compensation expense at the time the underlying commission is earned and begins to recognize 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 is recorded as a liability and will be reclassified to additional paid-in On a limited basis, the Company has issued stock options and RSUs that contain service, performance and market-based vesting conditions that include stock price targets to be met after the listing of the Company’s stock on a public exchange. Such awards are valued using a Monte Carlo simulation and the underlying expense will be recognized as the associated vesting conditions are met.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, consisting of legal, accounting and other fees and costs relating to the IPO, are capitalized and recorded on the condensed consolidated balance sheets. The deferred offering costs will be offset against the proceeds received upon the closing of the IPO. As of March 31, 2021 and December 31, 2020, $11.0 million and $1.8 million, respectively, of deferred offering costs were capitalized in Other non-current
New Accounting Pronouncements	New Accounting Pronouncements In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes Income Taxes step-up In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting

Business Combinations (Tables)

Business Combinations (Tables)	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
Summary of Changes in Contingent Consideration Measured at Fair Value on a Recurring Basis	Changes in contingent consideration measured at fair value on a recurring basis were as follows (in millions): Three Months Ended 2021 2020 Opening balance $ 39.8 $ 16.4 Acquisitions 2.0 — Payments and issuances (10.6 ) — Fair value (gains) losses included in net loss (3.2 ) 0.7 Closing Balance $ 28.0 $ 17.1

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Summary of Fair Value Measurements of Our Financial Instruments	The following table presents the balances of contingent consideration (in millions): March 31, 2021 December 31, Accrued expenses and other current liabilities $ 7.4 $ 19.1 Other non-current 20.6 20.7 Total contingent consideration $ 28.0 $ 39.8
Summary of Fair Value Measurement Inputs and Valuation Techniques	The following tables present quantitative information regarding the significant unobservable inputs utilized by the Company in the fair value measurement of Level 3 liabilities, consisting of different contingent consideration agreements, measured at fair value on a recurring basis: March 31, December 31, Discount rate 0.0% - 2.0% 0.0% - 2.0% Weighted average discount rate 1.7% 1.3% Earnings volatility 0% - 20% 0% - 18% Weighted-average earnings volatility 9.3% 6.9%

Convertible Preferred Stock a_2

Convertible Preferred Stock and Common stock (Tables)	3 Months Ended
	Mar. 31, 2021
Stockholders' Equity Note [Abstract]
Summary of Preferred Stock	March 31, 2021 Series of Convertible Preferred Stock Year Issued Shares Shares Issuance Price/ Price Aggregate Carrying Value Series A 2013 54,811,930 54,811,930 $ 1.0000 $ 54.8 $ 54.7 Series B 2014-2015 18,133,240 18,133,240 2.0766 37.7 37.5 Series C 2015-2016 13,580,260 13,580,260 4.0500 55.0 54.8 Series D 2016-2017 15,920,450 — 4.2632 — — Series E 2017-2018 78,543,890 78,543,890 6.7478 530.0 529.0 Series F 2018 33,686,160 33,686,160 11.8570 399.4 398.8 Series G 2019-2020 22,371,620 22,371,620 15.4269 345.1 344.3 237,047,550 221,127,100 $ 1,422.0 $ 1,419.1
Summary of Stock by Class	As of March 31, 2021, the Company had three classes of common stock: Class A common stock, Class B common stock and Class C common stock. Each class has par value of $0.00001. March 31, 2021 Shares Shares Shares Class A common stock 1,000,754,910 126,295,420 124,045,420 Class B common stock 270,618,860 4,562,160 4,562,160 Class C common stock 100,000,000 15,244,490 15,244,490 Total 1,371,373,770 146,102,070 143,852,070 As of December 31, 2020, the Company had two classes of common stock: Class A common stock and Class B common stock. Each class has a par value of $0.00001. December 31, 2020 Shares Shares Shares Class A common stock 530,136,050 118,549,390 116,299,390 Class B common stock 170,618,860 6,672,510 6,672,510 Total 700,754,910 125,221,900 122,971,900
Summary of Common Stock Reserved For Issuance	As of March 31, 2021 and December 31, 2020, the Company had shares of common stock reserved for issuance as follows: March 31, December 31, Convertible preferred stock outstanding 223,033,725 238,954,050 Options issued and outstanding 59,603,390 62,827,150 Restricted stock units issued and outstanding 50,272,925 32,556,160 Shares available for future stock-based incentive award issuances 41,105,315 11,679,150 Total 374,015,355 346,016,510

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Summary of Stock Option Activity	A summary of stock option activity under the 2012 Plan and the 2021 Plan, including 1,061,250 stock options that were granted outside of the 2012 Plan in 2019, is presented below (in millions, except share and per share amounts): Number of Weighted Weighted Average Aggregate Balances as of December 31, 2020 62,827,150 $ 4.55 7.8 $ 1,208.0 Granted 1,888,660 11.04 Exercised (4,710,490 ) 3.05 Forfeited (401,930 ) 6.35 Balances as of March 31, 2021 59,603,390 $ 4.86 7.7 $ 780.0 Exercisable and vested at March 31, 2021 32,491,554 $ 3.47 6.6 $ 470.6
Summary of Restricted Stock Units Activity	A summary of RSU activity under the 2012 Plan and the 2021 Plan is presented below: Number of Weighted Balances as of December 31, 2020 32,556,160 $ 6.75 Granted 18,088,710 12.61 Vested and converted to common stock — — Forfeited (371,945 ) 11.80 Balances as of March 31, 2021 50,272,925 $ 8.82
Summary of Share-based Payment Arrangement, Expensed and Capitalized, Amount	Total stock-based compensation expense included in the condensed consolidated statements of operations is as follows (in millions): Three Months Ended March 31, 2021 Three IPO Related Other Total March 31, Commissions and other related expense $ 41.7 $ 2.9 $ 44.6 $ 4.1 Sales and marketing 1.8 7.2 9.0 2.9 Operations and support 3.1 1.9 5.0 0.8 Research and development 46.9 2.6 49.5 0.5 General and administrative 55.0 4.4 59.4 2.8 Total stock-based compensation expense $ 148.5 $ 19.0 $ 167.5 $ 11.1

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Summary of Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders (in millions, except share and per share amounts): Three Months Ended March 31, 2021 2020 Numerator: Net loss attributable to common stockholders $ (212.4 ) $ (132.7 ) Denominator: Weighted-average number of shares outstanding used to compute net loss per share attributable to common stockholders, basic and diluted 126,917,284 108,764,426 Net loss per share attributable to common stockholders, basic and diluted $ (1.67 ) $ (1.22 )
Summary of Computation of Diluted Net Loss Per Share Attributable to Common Stockholders	The following participating securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented, because including them would have been anti-dilutive (on an as-converted Three Months Ended March 31, 2021 2020 Convertible preferred stock 223,033,725 248,336,668 Outstanding stock options 59,603,390 50,414,160 Outstanding RSUs 50,272,925 23,992,200 Unvested early exercised options 1,740,600 — Unvested common stock 525,930 9 83 Total 335,176,570 323,726,518

Compass Concierge Receivables_2

Compass Concierge Receivables and Allowance for Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2021
Receivables [Abstract]
Summary of ACL for Concierge Receivables	The following table summarizes the activity of the ACL for Concierge Receivables for the three months ended March 31, 2021 (in millions): Three Months Beginning of period $ 17.2 Allowances 1.9 Net write-offs and other (2.2 ) End of period $ 16.9
Summary of Aging Analysis of Concierge Receivables	The following tables present the aging analysis of Concierge Receivables as of March 31, 2021 (in millions): 31-90 days Over 90 Total Past Current Total March 31, 2021 $ 8.1 $ 13.8 $ 21.9 $ 43.3 $ 65.2

Restructuring Activities and _2

Restructuring Activities and COVID-19 Update (Tables)	3 Months Ended
	Mar. 31, 2021
Restructuring and Related Activities [Abstract]
Summary of restructuring costs	The expenses resulting from these cost-saving measures were included in the consolidated statement of operations for the three months ended March 31, 2020, as follows (in millions): Three Months Ended March 31, 2020 Severance Lease Total Sales and marketing $ 1.5 $ 1.2 $ 2.7 Operations and support 2.8 — 2.8 Research and development 0.7 — 0.7 General and administrative 0.4 — 0.4 Total $ 5.4 $ 1.2 $ 6.6

Business and Basis of Present_2

Business and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Millions	Apr. 01, 2021USD ($)$ / sharesshares	Mar. 19, 2021	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Date of incorporation			Oct. 4, 2012
Stock split ratio common stock		10
Deferred offering costs			$ 11	$ 1.8
Restricted Stock Units [Member] | Service Based And Liquidity Event Based [Member]
Allocated share based compensation			$ 148.5
Subsequent Event [Member]
Reclassification of convertible preferred stock into common stock | shares	223,033,725
Subsequent Event [Member] | Additional Paid-in Capital [Member]
Reclassification of convertible preferred stock into common stock value	$ 1,400
Subsequent Event [Member] | IPO [Member]
Stock shares issued during the period shares | shares	26,296,438
Sale of stock issue price per share | $ / shares	$ 18
Sale of stock net proceeds received on the transaction	$ 449.7
Deferred offering costs	$ 11

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2021
Accounting Policies [Line Items]
Deferred offering costs	$ 1.8		$ 11
Restricted Stock Units [Member]
Accounting Policies [Line Items]
Share based compensation by share based payment arrangement service based vesting period	4 years	4 years

Business Combinations - Additio

Business Combinations - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Business Acquisition [Line Items]
Payment to acquire business net of cash acquired	$ 59.2	$ 0.3
Restricted Stock Units (RSUs) [Member]
Business Acquisition [Line Items]
Share-based Payment Arrangement, Amount Capitalized	$ 2.5
Maximum [Member]
Business Acquisition [Line Items]
Finite lived intangible assets acquired remaining useful lives	5 years
Minimum [Member]
Business Acquisition [Line Items]
Finite lived intangible assets acquired remaining useful lives	4 years
2021 Acquistions [Member]
Business Acquisition [Line Items]
Payment to acquire business	$ 72.2
Business combination contingent consideration	2
Business combination operating lease right of use assets acquired	5.8
Goodwill arising out of business combination acquisitions	34.7
Business combination future consideration to be paid to the acquirees	29.3
Business acquistion compensation expenses	4.2	$ 1.3
Business combination other current assets and non current assets	5.4
Payment to acquire business net of cash acquired	59.2
Business combination other current and non current liabilities	3.8
Consideration of lease liability	5.8
2021 Acquistions [Member] | Accrued Expenses And Other Current Liabilities [Member]
Business Acquisition [Line Items]
Business combination contingent consideration	13
2021 Acquistions [Member] | Broker Relationships [Member]
Business Acquisition [Line Items]
Finite lived intangible assets acquired	31.4
2021 Acquistions [Member] | Trademarks [Member]
Business Acquisition [Line Items]
Finite lived intangible assets acquired	$ 6.5

Business Combinations - Summary

Business Combinations - Summary of Changes in Contingent Consideration Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Business Combinations [Abstract]
Opening balance	$ 39.8	$ 16.4
Acquisitions	2
Payments and issuances	(10.6)
Fair value (gains) losses included in net loss	(3.2)	0.7
Closing Balance	$ 28	$ 17.1

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Summary of Fair Value Measurements of Our Financial Instruments (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Accrued expenses and other current liabilities	$ 7.4	$ 19.1
Other non-current liabilities	20.6	20.7
Total contingent consideration	$ 28	$ 39.8	$ 17.1	$ 16.4

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Summary of Fair Value Measurement Inputs and Valuation Techniques (Detail)	Mar. 31, 2021	Dec. 31, 2020
Measurement Input, Discount Rate [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination contingent consideration liability measurement input	0.020	0.020
Measurement Input, Discount Rate [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination contingent consideration liability measurement input	0	0
Measurement Input, Discount Rate [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination contingent consideration liability measurement input	0.017	0.013
Measurement Input Earnings Volatility [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination contingent consideration liability measurement input	2,000	1,800
Measurement Input Earnings Volatility [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination contingent consideration liability measurement input	0	0
Measurement Input Earnings Volatility [Member] | Weighted Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Business combination contingent consideration liability measurement input	0.093	0.069

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Business Combinations contingent liabilities undiscounted maximum payment	$ 85,500,000
Business Combinations contingent liabilities undiscounted maximum payment term	5 years
Fair value transfers Into levels of financial instruments	$ 0
Fair Value, Inputs, Level 3 [Member]
Business combination contingent consideration fair value disclosure	28,000,000	$ 39,800,000
Cash And Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents fair value disclosure	$ 329,600,000	$ 440,100,000

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($) $ in Millions	Jul. 31, 2020	Mar. 31, 2021	Dec. 31, 2020
Concierge Revolving Credit Facility [Member]
Debt [Line Items]
Maximum borrowing capacity	$ 75
Interest rate basis	3.00
Unused capacity commitment fee percentage	0.50%
Line of credit facility expiration month and year		2022
Debt instrument interest rate	3.22%
Line of credit		$ 10.2	$ 8.4
Covenant compliance		the Company was in compliance with the covenants under the Concierge Facility.
Debt issuance costs		$ 1.4
Revolving Credit Facility [Member]
Debt [Line Items]
Maximum borrowing capacity		$ 350
Interest rate basis		1.00
Unused capacity commitment fee percentage		0.175%
Line of credit facility expiration month and year		2026
Additional borrowing capacity		$ 250
Additional borrowing capacity percentage threshold to assets		18.50%
Net leverage ratio		4.50
Letters of credit		$ 125
Minimum liquidity		$ 150
Revolving Credit Facility [Member] | Other Current Assets [Member]
Debt [Line Items]
Covenant compliance		the Company was in compliance with the covenants under the Revolving Credit Facility.
Debt issuance costs		$ 1.4
Revolving Credit Facility [Member] | Base Rate [Member]
Debt [Line Items]
Interest rate basis		0.50
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt [Line Items]
Interest rate basis		1.50
Revolving Credit Facility [Member] | Federal Funds Effective Swap Rate [Member]
Debt [Line Items]
Interest rate basis		0.50
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) Swap Rate [Member]
Debt [Line Items]
Interest rate basis		1.00
Revolving Credit Facility [Member] | Debt Default Interest Rate [Member]
Debt [Line Items]
Interest rate basis		2.0

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Escrow and trust deposits	$ 238.7	$ 46.1
Letters of credit	$ 51.7	$ 50.7

Convertible Preferred Stock a_3

Convertible Preferred Stock and Common stock - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2021	Feb. 28, 2021	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Apr. 30, 2021	Apr. 01, 2021	Dec. 31, 2020
Proceeds from Issuance of Convertible Preferred Stock					$ 0	$ 1
Common stock shares authorized	1,371,373,770		1,371,373,770		1,371,373,770				700,754,910
Series D Convertible Preferred Stock [Member]
Conversion of Stock, Shares Converted			15,920,450
Series G Convertible Preferred Stock [Member]
Temporary Equity Stock Issued During Period Shares New Issues				64,820
Proceeds from Issuance of Convertible Preferred Stock				$ 1
Common Class A [Member]
Conversion of Stock, Shares Converted	15,244,490
Convertible Preferred Stock, Shares Issued upon Conversion								223,033,725
Treasury Stock, Common, Shares	2,250,000		2,250,000		2,250,000				2,250,000
Common stock shares authorized	1,000,754,910		1,000,754,910		1,000,754,910				530,136,050
Common Class A [Member] | Subsequent Event [Member] | Restated Certifiacte Of Incorporation Member [Member]
Common stock shares authorized							12,500,000,000
Common Class C [Member]
Conversion of Stock, Shares Issued	15,244,490
Common Stock, Voting Rights		Each share of Class C common stock is entitled to twenty votes
Common stock shares authorized	100,000,000		100,000,000		100,000,000
Common Class C [Member] | Subsequent Event [Member] | Restated Certifiacte Of Incorporation Member [Member]
Common stock shares authorized							100,000,000
Common Class B [Member]
Common stock shares authorized	270,618,860		270,618,860		270,618,860				170,618,860
Common Class B [Member] | Subsequent Event [Member] | Restated Certifiacte Of Incorporation Member [Member]
Common stock shares authorized							1,250,000,000
Undesignated Preferred Stock [Member] | Subsequent Event [Member] | Restated Certifiacte Of Incorporation Member [Member]
Preferred stock shares authorized							25,000,000

Convertible Preferred Stock a_4

Convertible Preferred Stock and Common stock - Summary of Preferred Stock (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Shares Authorized	237,047,550	246,430,170
Shares Issued and Outstanding	221,127,100	237,047,550
Issuance Price/ Liquidation Price (Per Share)	$ 0.00001	$ 0.00001
Aggregate Liquidation Value	$ 1,422
Carrying Value (Net of Issuance Costs)	$ 1,419.1
Series A [Member]
Year Issued	2013
Shares Authorized	54,811,930
Shares Issued and Outstanding	54,811,930
Issuance Price/ Liquidation Price (Per Share)	$ 1
Aggregate Liquidation Value	$ 54.8
Carrying Value (Net of Issuance Costs)	$ 54.7
Series B [Member]
Year Issued	2014-2015
Shares Authorized	18,133,240
Shares Issued and Outstanding	18,133,240
Issuance Price/ Liquidation Price (Per Share)	$ 2.0766
Aggregate Liquidation Value	$ 37.7
Carrying Value (Net of Issuance Costs)	$ 37.5
Series C [Member]
Year Issued	2015-2016
Shares Authorized	13,580,260
Shares Issued and Outstanding	13,580,260
Issuance Price/ Liquidation Price (Per Share)	$ 4.0500
Aggregate Liquidation Value	$ 55
Carrying Value (Net of Issuance Costs)	$ 54.8
Series D [Member]
Year Issued	2016-2017
Shares Authorized	15,920,450
Issuance Price/ Liquidation Price (Per Share)	$ 4.2632
Series E [Member]
Year Issued	2017-2018
Shares Authorized	78,543,890
Shares Issued and Outstanding	78,543,890
Issuance Price/ Liquidation Price (Per Share)	$ 6.7478
Aggregate Liquidation Value	$ 530
Carrying Value (Net of Issuance Costs)	$ 529
Series F [Member]
Year Issued	2018
Shares Authorized	33,686,160
Shares Issued and Outstanding	33,686,160
Issuance Price/ Liquidation Price (Per Share)	$ 11.8570
Aggregate Liquidation Value	$ 399.4
Carrying Value (Net of Issuance Costs)	$ 398.8
Series G [Member]
Year Issued	2019-2020
Shares Authorized	22,371,620
Shares Issued and Outstanding	22,371,620
Issuance Price/ Liquidation Price (Per Share)	$ 15.4269
Aggregate Liquidation Value	$ 345.1
Carrying Value (Net of Issuance Costs)	$ 344.3

Convertible Preferred Stock a_5

Convertible Preferred Stock and Common stock - Schedule of Stock by Class (Detail) - shares	Mar. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Shares Authorized	1,371,373,770	700,754,910
Shares Issued	146,102,070	125,221,900
Shares Outstanding	143,852,070	122,971,900
Class A common stock [Member]
Class of Stock [Line Items]
Shares Authorized	1,000,754,910	530,136,050
Shares Issued	126,295,420	118,549,390
Shares Outstanding	124,045,420	116,299,390
Class B common stock [Member]
Class of Stock [Line Items]
Shares Authorized	270,618,860	170,618,860
Shares Issued	4,562,160	6,672,510
Shares Outstanding	4,562,160	6,672,510
Class C common stock [Member]
Class of Stock [Line Items]
Shares Authorized	100,000,000
Shares Issued	15,244,490
Shares Outstanding	15,244,490

Convertible Preferred Stock a_6

Convertible Preferred Stock and Common stock - Summary of Common Stock Reserved For Issuance (Detail) - shares	Mar. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common stock reserved for issuance	374,015,355	346,016,510
Convertible preferred stock outstanding [Member]
Class of Stock [Line Items]
Common stock reserved for issuance	223,033,725	238,954,050
Options issued and outstanding [Member]
Class of Stock [Line Items]
Common stock reserved for issuance	59,603,390	62,827,150
Restricted stock units issued and outstanding [Member]
Class of Stock [Line Items]
Common stock reserved for issuance	50,272,925	32,556,160
Shares available for future stock-based incentive award issuances [Member]
Class of Stock [Line Items]
Common stock reserved for issuance	41,105,315	11,679,150

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	Feb. 28, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted during the period		737,560		1,061,250
Intrinsic value of stock options exercised		$ 79,800,000	$ 500,000
Allocated share based compensation expense		167,500,000	11,100,000
Options unrecognized compensation		$ 451,500,000
Options unrecognized compensation period of recognition		3 years 4 months 24 days
Proceeds from exercise of stock options		$ 14,400,000	$ 200,000
Share based compensation by share based payment arrangement stock options granted during the period		1,888,660
Other non-current liabilities		$ 26,700,000			$ 23,500,000
SHARES Granted Under Stock Plans Subject To Repurchase [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares subject to repurchase		1,740,600
Ipo Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation expense		$ 148,500,000
Performance Shares [Member] | Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation expense		$ 0
Share-based compensation arrangement by share based payment award restricted stock units granted		8,611,810
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from exercise of stock options		$ 4,500,000
Other non-current liabilities		$ 9,000,000
2012 Stock Incentive Plan [Member] | Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term		10 years
2012 Stock Incentive Plan [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term		7 years
2021 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	29,666,480	41,105,315
2021 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	7,416,620
Share based compensation by share based payment arrangement increase in the shares authorised for issuance as a percentage of shares outstanding	1.00%
Share based compensation by share based payment arrangement stock options granted during the period	0
2021 Employee Stock Purchase Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	150,000,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Share-based Payment Arrangement, Additional Disclosure [Abstract]
Number of Shares, Opening Balance	62,827,150
Number of Shares, Granted	1,888,660
Number of Shares, Exercised	(4,710,490)
Number of Shares, Forfeited	(401,930)
Number of Shares, Ending Balance	59,603,390	62,827,150
Exercisable and vested	32,491,554
Weighted Average Exercise Price, Opening Balance	$ 4.55
Weighted Average Exercise Price,Granted	11.04
Weighted Average Exercise Price,Exercised	3.05
Weighted Average Exercise Price,Forfeited	6.35
Weighted Average Exercise Price, Ending Balance	4.86	$ 4.55
Weighted Average Exercise Price, Exercisable and vested	$ 3.47
Weighted Average Remaining Contract Term, December 31, 2020	7 years 8 months 12 days	7 years 9 months 18 days
Weighted Average Remaining Contract Term, March 31, 2021	7 years 8 months 12 days	7 years 9 months 18 days
Weighted Average Remaining Contract Term, Exercisable and vested	6 years 7 months 6 days
Aggregate Intrinsic Value	$ 780	$ 1,208
Aggregate Intrinsic Value, Exercisable and vested	$ 470.6

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Restricted Stock Units Activity (Detail)	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Share-based Payment Arrangement [Abstract]
Number of Shares, Opening Balance | shares	32,556,160
Number of Shares, Granted | shares	18,088,710
Number of Shares, Vested and converted to common stock | shares	0
Number of Shares, Forfeited | shares	(371,945)
Number of Shares, Ending Balance | shares	50,272,925
Weighted Average Grant Date Fair Value, Opening Balance | $ / shares	$ 6.75
Weighted Average Grant Date Fair Value, Granted | $ / shares	12.61
Weighted Average Grant Date Fair Value, Vested and converted to common stock | $ / shares	0
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	11.80
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 8.82

Stock-Based Compensation - Shar

Stock-Based Compensation - Share-based Payment Arrangement, Expensed and Capitalized, Amount (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 167.5	$ 11.1
Commissions and other related expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	44.6	4.1
Sales and marketing [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	9	2.9
Operations and support [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	5	0.8
Research and development[Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	49.5	0.5
General and administrative [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	59.4	$ 2.8
IPO Related Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	148.5
IPO Related Expense [Member] | Commissions and other related expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	41.7
IPO Related Expense [Member] | Sales and marketing [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1.8
IPO Related Expense [Member] | Operations and support [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	3.1
IPO Related Expense [Member] | Research and development[Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	46.9
IPO Related Expense [Member] | General and administrative [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	55
Other Expense [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	19
Other Expense [Member] | Commissions and other related expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	2.9
Other Expense [Member] | Sales and marketing [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	7.2
Other Expense [Member] | Operations and support [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1.9
Other Expense [Member] | Research and development[Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	2.6
Other Expense [Member] | General and administrative [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 4.4

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income tax expense benefit	$ 0.7	$ 0

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Schedule of Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Diluted net loss per share attributable to common stockholders	335,176,570	323,726,518
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Diluted net loss per share attributable to common stockholders	223,033,725	248,336,668
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Diluted net loss per share attributable to common stockholders	59,603,390	50,414,160
Outstanding RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Diluted net loss per share attributable to common stockholders	50,272,925	23,992,200
Unvested early exercised options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Diluted net loss per share attributable to common stockholders	1,740,600
Unvested common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Diluted net loss per share attributable to common stockholders	525,930	983,490

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Schedule of Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net loss attributable to common stockholders	$ (212.4)	$ (132.7)
Denominator:
Weighted-average number of shares outstanding used to compute net loss per share attributable to common stockholders, basic and diluted	126,917,284	108,764,426
Net loss per share attributable to common stockholders, basic and diluted	$ (1.67)	$ (1.22)

Compass Concierge Receivables_3

Compass Concierge Receivables and Allowance for Credit Losses - Additional Information (Detail)	Mar. 31, 2021	Dec. 31, 2020
Receivables [Abstract]
Percentage of financing receivables related to unsold properties	95.00%	93.00%

Compass Concierge Receivables_4

Compass Concierge Receivables and Allowance for Credit Losses - Summary of ACL for Concierge Receivables (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)
Accounting Policies [Abstract]
Beginning of period	$ 17.2
Allowances	1.9
Net write-offs and other	(2.2)
End of period	$ 16.9

Compass Concierge Receivables_5

Compass Concierge Receivables and Allowance for Credit Losses - Summary of Aging Analysis of Concierge Receivables (Detail) $ in Millions	Mar. 31, 2021USD ($)
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 21.9
Financing Receivable, Not Past Due	43.3
Financing Receivable, before Allowance for Credit Loss	65.2
Financing Receivables Overdue Up to Thirty One Days And Less Than Ninety Days [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	8.1
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 13.8

Restructuring Activities and _3

Restructuring Activities and COVID -19 Update - Summary of restructuring costs (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 6.6
Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	5.4
Lease Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	1.2
Sales and marketing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	2.7
Sales and marketing [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	1.5
Sales and marketing [Member] | Lease Termination [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	1.2
Operations and support [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	2.8
Operations and support [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	2.8
Research and development[Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.7
Research and development[Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.7
General and administrative [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	0.4
General and administrative [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 0.4

Restructuring Activities and _4

Restructuring Activities and COVID -19 Update - Additional Information (Detail) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Restructuring and Related Activities [Abstract]
Restructuring and Related Cost, Number of Positions Eliminated, Percent	15.00%
Liabilities related to restructuring costs	$ 0	$ 0