Redfin (RDFN) 10-Q 8 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2018	Nov. 01, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Redfin Corp
Entity Central Index Key	1,382,821
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		89,526,072

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 448,968	$ 208,342
Restricted cash	11,968	4,316
Prepaid expenses	5,933	8,613
Accrued revenue, net	13,254	13,334
Inventory	25,161	3,382
Loans held for sale	5,921	1,891
Other current assets	989	328
Total current assets	512,194	240,206
Property and equipment, net	23,361	22,318
Intangible assets, net	2,928	3,294
Goodwill	9,186	9,186
Other assets	7,248	6,951
Total assets	554,917	281,955
Current liabilities:
Accounts payable	2,601	1,901
Accrued liabilities	37,532	26,605
Other payables	12,167	4,068
Loan facility	5,790	2,016
Current portion of deferred rent	1,691	1,267
Total current liabilities	59,781	35,857
Deferred rent, net of current portion	10,258	10,668
Convertible senior notes, net	112,130	0
Total liabilities	182,169	46,525
Commitments and contingencies (Note 11)
Stockholders’ equity:
Common stock—par value $0.001 per share; 500,000,000 shares authorized; 89,234,819 and 81,468,891 shares issued and outstanding, respectively	89	81
Preferred stock—par value $0.001 per share; 10,000,000 shares authorized and no shares issued and outstanding	0	0
Additional paid-in capital	531,418	364,352
Accumulated deficit	(158,759)	(129,003)
Total stockholders’ equity	372,748	235,430
Total liabilities and stockholders’ equity	$ 554,917	$ 281,955

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	500,000,000	500,000,000
Common stock, issued (in shares)	89,234,819	81,468,891
Common stock, outstanding (in shares)	89,234,819	81,468,891
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenue	$ 140,255	$ 109,479	$ 362,791	$ 274,282
Cost of revenue	97,950	70,166	269,576	191,633
Gross profit	42,305	39,313	93,215	82,649
Operating expenses:
Technology and development	14,310	11,483	40,105	31,245
Marketing	8,236	5,588	36,006	26,179
General and administrative	16,470	11,995	48,532	38,828
Total operating expenses	39,016	29,066	124,643	96,252
Income (loss) from operations	3,289	10,247	(31,428)	(13,603)
Interest income	1,775	311	3,082	387
Interest expense	(1,610)	0	(1,610)	0
Other income, net	21	0	200	13
Net income (loss)	3,475	10,558	(29,756)	(13,203)
Accretion of redeemable convertible preferred stock	0	(40,224)	0	(175,915)
Net income (loss) attributable to common stock—basic	3,475	(29,666)	(29,756)	(189,118)
Net income (loss) attributable to common stock—diluted	$ 3,475	$ (29,666)	$ (29,756)	$ (189,118)
Net income (loss) attributable to common stock—basic (in dollars per share)	$ 0.04	$ (0.50)	$ (0.35)	$ (6.37)
Net income (loss) attributable to common stock—diluted (in dollars per share)	$ 0.04	$ (0.50)	$ (0.35)	$ (6.37)
Weighted average shares—basic (in shares)	87,743,223	58,868,903	84,327,266	29,678,082
Weighted average shares—diluted (in shares)	94,642,463	58,868,903	84,327,266	29,678,082

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Operating activities:
Net loss	$ 3,475	$ 10,558	$ (29,756)	$ (13,203)	$ (15,002)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization			6,123	5,326
Stock-based compensation			14,472	8,028
Amortization of debt discount and issuance costs			1,128	0
Change in assets and liabilities:
Prepaid expenses			2,680	(84)
Accrued revenue			80	(2,712)
Inventory			(21,779)	(5,399)
Other current assets			(576)	8,556
Other long-term assets			(296)	244
Accounts payable			702	1,228
Accrued liabilities			10,943	8,513
Deferred lease liability			(913)	1,001
Accrued expenses			414	0
Origination of loans held for sale			(56,157)	(5,755)
Proceeds from sale of loans originated as held for sale			52,127	5,030
Net cash provided by (used in) operating activities			(20,808)	10,773
Investing activities:
Maturities and sales of short-term investments			0	1,484
Purchases of short-term investments			0	(993)
Purchases of property and equipment			(5,528)	(10,499)
Net cash used in investing activities			(5,528)	(10,008)
Financing activities:
Proceeds from issuance of convertible senior notes, net			138,953	0
Proceeds from follow-on offering, net			107,593	0
Proceeds from issuance of common stock			17,314	2,519
Tax payment related to net share settlements on restricted stock units			(705)	0
Proceeds from initial public offering, net of underwriting discounts			0	148,088
Payment of initial public offering costs			0	(3,449)
Borrowings from warehouse credit facilities			54,806	5,603
Repayments of warehouse credit facilities			(51,031)	(4,898)
Other payables - customer escrow deposits related to title services			7,684	6,065
Net cash provided by financing activities			274,614	153,928
Net change in cash, cash equivalents, and restricted cash			248,278	154,693
Cash, cash equivalents, and restricted cash:
Beginning of period			212,658	67,845	67,845
End of period	460,936	222,538	460,936	222,538	$ 212,658
Supplemental disclosure of non-cash investing and financing activities:
Accretion of redeemable convertible preferred stock	$ 0	$ (40,224)	0	(175,915)
Stock-based compensation capitalized in property and equipment			(363)	(194)
Initial public offering cost accruals			0	(200)
Property and equipment additions in accounts payable and accrued expenses			(25)	0
Leasehold improvements paid directly by lessor			(926)	(104)
Cash in transit for exercised stock options			$ (85)	$ 0

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Cumulative stock-based compensation adjustment	$ 0		$ 522	$ (522)
Redeemable convertible preferred stock beginning balance (in shares) at Dec. 31, 2016	55,422,002
Redeemable convertible preferred stock beginning balance at Dec. 31, 2016	$ 655,416
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock	$ 175,915
Conversion of redeemable convertible preferred stock to common stock (in shares)	(55,422,002)
Conversion of redeemable convertible preferred stock to common stock	$ (831,331)
Redeemable convertible preferred stock ending balance (in shares) at Dec. 31, 2017	0
Redeemable convertible preferred stock ending balance at Dec. 31, 2017	$ 0
Common stock, outstanding, beginning balance (in shares) at Dec. 31, 2016		14,687,024
Total stockholders' deficit, beginning balance at Dec. 31, 2016	(563,734)	$ 15	0	(563,749)
Increase (Decrease) in Stockholders' Equity
Proceeds from initial public offering, net of underwriters' discounts/Issuance of common stock related to follow-on offering, net (in shares)		10,615,650
Proceeds from initial public offering, net of underwriters' discounts/Issuance of common stock related to follow-on offering, net	148,088	$ 10	148,078
Initial public offering costs	(3,708)		(3,708)
Exercise of stock options (in shares)		744,215
Exercise of stock options	3,001	$ 1	3,000
Stock-based compensation	11,369		11,369
Accretion of redeemable convertible preferred stock	(175,915)		(8,690)	(167,225)
Conversion of redeemable convertible preferred stock to common stock (in shares)		55,422,002
Conversion of redeemable convertible preferred stock to common stock	831,331	$ 55	213,781	617,495
Net loss	$ (15,002)			(15,002)
Common stock, outstanding, ending balance (in shares) at Dec. 31, 2017	81,468,891	81,468,891
Total stockholders' deficit, ending balance at Dec. 31, 2017	$ 235,430	$ 81	364,352	(129,003)
Redeemable convertible preferred stock ending balance (in shares) at Sep. 30, 2018	0
Redeemable convertible preferred stock ending balance at Sep. 30, 2018	$ 0
Increase (Decrease) in Stockholders' Equity
Proceeds from initial public offering, net of underwriters' discounts/Issuance of common stock related to follow-on offering, net (in shares)		4,836,336
Proceeds from initial public offering, net of underwriters' discounts/Issuance of common stock related to follow-on offering, net	107,593	$ 5	107,588
Issuance of common stock pursuant to employee stock purchase program (in shares)		187,076
Issuance of common stock pursuant to employee stock purchase program	$ 3,672		3,672
Exercise of stock options (in shares)	2,653,008	2,653,008
Exercise of stock options	$ 13,728	$ 3	13,725
Issuance of common stock pursuant to restricted stock units (in shares)		127,746
Issuance of common stock pursuant to restricted stock units	0	$ 0
Restricted stock surrendered for employees' tax liability (in shares)		(38,238)
Restricted stock surrendered for employees' tax liability	(705)		(705)
Equity component of convertible senior notes, net	27,951		27,951
Stock-based compensation	14,835		14,835
Net loss	$ (29,756)			(29,756)
Common stock, outstanding, ending balance (in shares) at Sep. 30, 2018	89,234,819	89,234,819
Total stockholders' deficit, ending balance at Sep. 30, 2018	$ 372,748	$ 89	$ 531,418	$ (158,759)

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Summary of Significant Accounting Policies	Description of Business and Summary of Significant Accounting Policies Description of Business — Redfin Corporation (“Redfin” or the “Company”) was incorporated in October 2002 and is headquartered in Seattle, Washington. The Company operates an online real estate marketplace and provides real estate services, including assisting individuals in the purchase or sale of their residential property. The Company also provides title and settlement services, originates and sells mortgages, and buys and sells residential properties via wholly owned subsidiaries. The Company has operations located in multiple states nationwide. Initial Public Offering — On August 2, 2017, the Company completed an initial public offering (the "IPO") whereby 10,615,650 shares of common stock were sold at a price of $15.00 per share, which included 1,384,650 shares pursuant to the underwriters' option to purchase additional shares. The Company received net proceeds of approximately $144,380 after deducting the underwriting discount and offering expenses directly attributable to the IPO. Upon the closing of the IPO, all shares of the outstanding redeemable convertible preferred stock automatically converted into 55,422,002 shares of common stock on a one -for-one basis. Initial Public Offering Costs — Costs, including legal, accounting and other fees and costs relating to the IPO, were accounted for as a reduction in additional paid-in capital. Aggregate offering expenses totaled $3,708 . Follow-on Offerings — On July 23, 2018, the Company completed follow-on public offerings of 4,836,336 shares of common stock (including 630,826 shares pursuant to the underwriters’ option to purchase additional shares) and $143,750 aggregate principal amount of 1.75% Convertible Senior Notes due 2023 (the "Notes") (including $18,750 principal amount of Notes sold pursuant to the underwriters’ option to purchase additional Notes). The public offering price for our common stock offering was $23.50 per share. The Company received net proceeds of approximately $107,593 from the common stock offering and $138,953 from the Notes offering, in each case after deducting the underwriting discounts and issuance costs directly attributable to each offering. Follow-on Offerings Costs — Costs include legal, accounting and other fees and costs relating to both the common stock offering and the Notes offering. Aggregate issuance costs totaled $862 . Basis of Presentation — The consolidated financial statements and accompanying notes have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”). The Company had no components of other comprehensive income (loss) during any of the periods presented, as such, a consolidated statement of comprehensive income (loss) is not presented. All amounts are presented in thousands, except share and per share data. The unaudited condensed consolidated interim financial statements, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary to present fairly the Company's financial position as of September 30, 2018 , the Company's results of operations for the three and nine months ended September 30, 2018 and 2017, and the Company's cash flows for the nine months ended September 30, 2018 and 2017. The results for the three and nine months ended September 30, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any interim period or for any other future year. Principles of Consolidation —The unaudited condensed consolidated interim financial statements include the accounts of Redfin and its wholly owned subsidiaries. Intercompany transactions and balances have been eliminated. Certain Significant Risks and Business Uncertainties — The Company is subject to the risks and challenges associated with companies at a similar stage of development. These include dependence on key individuals, successful development and marketing of its offerings, and competition with larger companies with greater financial, technical, and marketing resources. Further, to achieve substantially higher revenue in order to become profitable, the Company may require additional funds that may not be available or may not be on terms that are acceptable to the Company. The Company operates in the online real estate marketplace and, accordingly, can be affected by a variety of factors. For example, management of the Company believes that any of the following factors could have a significant negative effect on the Company’s future financial position, results of operations, and cash flows: unanticipated fluctuations in operating results due to seasonality and cyclicality in the real estate industry, changes in home sale prices and transaction volumes, the Company’s ability to increase market share, competition and U.S. economic conditions. Since inception through September 30, 2018 , the Company has incurred losses from operations and accumulated a deficit of $158,759 , during which it has been dependent on equity financing to fund operations. Use of Estimates — The preparation of consolidated financial statements, in conformity with GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and results of operations during the respective periods. The Company’s more significant estimates include, but are not limited to, valuation of deferred income taxes, stock-based compensation, net realizable value of inventory, prior to its conversion on August 2, 2017 the fair value of common stock and redeemable convertible preferred stock, capitalization of website development costs, recoverability of intangible assets with finite lives, fair value of reporting units for purposes of evaluating goodwill for impairment, and the fair value of the convertible feature related to the Notes (see Note 15). The amounts ultimately realized from the affected assets or ultimately recognized as liabilities will depend on, among other factors, general business conditions and could differ materially in the near term from the carrying amounts reflected in the consolidated financial statements. Significant Accounting Policies —There have been no material changes to the Company's significant accounting policies during the nine months ended September 30, 2018 , from the significant accounting policies included in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2017, except as noted below. Recently Adopted Accounting Pronouncements — In May 2014, the Financial Accounting Standards Board ("FASB") issued a new Accounting Standard Update ("ASU") 2014-09, Revenue from Contracts with Customers (Topic 606) . This guidance provides that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance also requires more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The Company adopted ASU 2014-09 and its related amendments (collectively known as ASC 606) effective on January 1, 2018, using the modified retrospective adoption methodology. Real estate services, properties and other revenue contain single performance obligations and the Company believes the timing of the satisfaction of the performance obligations, triggering the recognition of revenue, did not differ from the Company's timing for recognizing revenue prior to adopting this pronouncement. Further description of the impact of this pronouncement is included in Note 2: Revenue from Contracts with Customers. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230). This guidance impacts the classification of certain cash receipts and cash payments in the statement of cash flows. The new standard made eight targeted changes to how cash receipts and cash payments are presented and classified in the statement of cash flows. The Company adopted the new standard on a retrospective basis on January 1, 2018. The adoption of this standard had no impact on the Company’s statement of cash flows. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash . This guidance impacts the classification and presentation of changes in restricted cash on the statement of cash flows. This guidance is effective for interim and annual reporting periods beginning after December 15, 2017, and early adoption is permitted. The adoption of this guidance requires a retrospective transition method to each period presented. The Company early adopted this guidance on October 1, 2017. Upon adoption, the following balances were reclassified: restricted cash to the reconciliation of change in cash, cash equivalents and restricted cash, and other payables related to cash held in escrow on behalf of customers to financing activities. In the Company’s capacity as fiduciary, the cash receipt is a function of providing the customer with a service (title). Therefore, the escrow funds payable are akin to a repayment of debt, a financing activity, whereby the Company in its role as fiduciary is temporarily holding cash in its restricted accounts on behalf of its customers and subsequently releases the cash to settle the customers' contractual obligation. This reclassification will maintain an accurate reflection of the Company's cash flows from operating and financing activities. The reconciliation of amounts previously reported to the revised amounts upon adoption are as follows: Nine Months Ended September 30, 2017 Previously reported Adjustments As revised Cash provided by operating activities $ 10,551 $ 222 $ 10,773 Cash provided by financing activities $ 147,863 $ 6,065 $ 153,928 Net change in cash, cash equivalents, and restricted cash (1) $ 148,406 $ 6,287 $ 154,693 (1) Previously titled: net change in cash and cash equivalents Recently Issued Accounting Pronouncements — In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) . This standard requires the recognition of a right-of-use asset and lease liability on the balance sheet for all leases. This standard also requires more detailed disclosures to enable users of financial statements to understand the amount, timing, and uncertainty of cash flows arising from leases. This guidance is effective for interim and annual reporting periods beginning after December 15, 2018. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842) providing an optional alternative transition method to the modified retrospective approach whereby under this optional transition method an entity initially applies the new leases standard at the adoption date and recognizes a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In addition, this ASU provides a practical expedient, by class of underlying asset, to not separate non-lease components from the associated lease and instead account for the lease as a single component if both the timing and pattern of transfer of the non-lease component(s) are the same, and if the lease would be classified as an operating lease. These amendments have the same effective date as ASU 2016-02. Early adoption is permitted for both ASU 2016-02 and 2018-11. The Company plans to elect the optional transition method on the adoption date of January 1, 2019. The Company is in the process of evaluating the impact of adoption of the ASU on its consolidated financial statements, including implementing changes to its systems, processes, and internal controls. It is believed the most significant change will relate to the recognition of right-of-use assets and lease liabilities on the Company’s balance sheet for real estate leases that are currently accounted for as operating leases, as well as the accompanying disclosures. The Company is unable to estimate the impact at this time but believes it will be material. In August 2018, the Securities and Exchange Commission (the "SEC") adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification , amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. This final rule became effective on November 5, 2018, but the staff of the SEC provided relief on the effective date of the rule with respect to the analysis of stockholders' equity until the Company's Form 10-Q for its fiscal quarter ending March 31, 2019. The Company is in the process of evaluating the impact of the final rule on its condensed consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) , which modifies the disclosures on fair value measurements by removing the requirement to disclose the amount and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy and the policy for timing of such transfers. The ASU expands the disclosure requirements for Level 3 fair value measurements, primarily focused on changes in unrealized gains and losses included in other comprehensive income. The ASU is effective for public entities for fiscal years beginning after December 15, 2019, with early adoption permitted. The Company has not yet completed its assessment of the impact of the new standard on the Company’s Consolidated Financial Statements. In August 2018, the FASB issued authoritative guidance under ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract . The ASU requires implementation costs incurred by customers in cloud computing arrangements (i.e., hosting arrangements) to be capitalized under the same premises of authoritative guidance for internal-use software, and deferred over the noncancellable term of the cloud computing arrangements plus any option renewal periods that are reasonably certain to be exercised by the customer or for which the exercise is controlled by the service provider. The ASU is effective in the first quarter of fiscal 2021. The Company is currently in the process of evaluating the impact of the final rule on its consolidated financial statements.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Revenue from Contracts with Customers Revenue Recognition — The Company applies the provisions of ASC 606-10, Revenue from Contracts with Customers ("ASC 606"), and all related appropriate guidance. The Company recognizes revenue under the core principle to depict the transfer of control to the Company’s customers in an amount reflecting the consideration the Company expects to be entitled. In order to achieve that core principle, the Company applies the following five step approach: (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract, and (5) recognize revenue when a performance obligation is satisfied. The Company’s revenue primarily consists of commissions and fees charged on each real estate services transaction completed by the Company or its partner agents. The Company’s key revenue components are brokerage revenue, partner revenue, property sales revenue, and other revenue. Revenue earned but not received is recorded as accrued revenue on the accompanying consolidated balance sheets, net of an allowance for doubtful accounts. The Company does not separately disclose the amounts of product and service revenue. Cost of Revenue —C ost of revenue consists primarily of personnel costs (including base pay, benefits, and stock-based compensation), transaction bonuses, home-touring and field expenses, listing expenses, property costs related to our properties segment, office and occupancy expenses, and depreciation and amortization related to fixed assets and acquired intangible assets. Property costs related to our properties segment include the property purchase price, capitalized improvements, selling expenses directly attributable to the transaction, and property maintenance expenses. Nature and Disaggregation of Revenue Real Estate Services Brokerage Revenue— The Company recognizes commission-based brokerage revenue upon closing of a real estate services transaction, net of any commission refund or any closing-cost reduction. Brokerage revenue includes the Company's offer and listing services, representing homebuyers and home sellers. The transaction price is calculated by taking the agreed upon commission rate and applying that to the home's selling price. Brokerage revenue contains a single performance obligation that is satisfied upon the closing of a real estate services transaction, at which point the entire transaction price is earned. The Company is not entitled to any commission until the performance obligation is satisfied and is not owed any commission for unsuccessful transactions, even if services have been provided. Partner Revenue— Partner revenue consists of fees earned by referring customers to partner agents. Partner revenue is earned and recognized when partner agents close referred transactions, net of any refunds provided to customers. The transaction price is a fixed percentage of the partner agent's commission. The partner agent directly remits the referral fee revenue to the Company. The Company is not entitled to any referral fee revenue until the related referred real estate services transaction closes, at which point the entire transaction price is earned and recognized as revenue. Properties Properties Revenue— Properties revenue consists of revenue earned when the Company sells homes that it previously bought directly from homeowners . Properties revenue is recorded at closing on a gross basis, representing the sales price of the home. The Company does not offer warranties for sold homes, and there are no continuing performance obligations following the transaction close date. Other Other Revenue— Substantially all fees and revenue from other services are recognized when the service is provided. Other services revenue includes fees earned from mortgage banking services, title settlement services, Walk Score data services, and advertising. Mortgage banking services are not subject to the guidance in ASC 606 as the scope of the standard does not apply to revenue on contracts accounted for under Transfers and Servicing (Topic 860) but are included in other services revenue to reconcile total revenue presented on the condensed consolidated statements of operations to the disaggregation of revenue table below. The Company's revenue from contracts with customers for the various revenue categories is as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 Real estate services Brokerage revenue $ 118,809 $ 97,787 $ 312,306 $ 247,327 Partner revenue 7,456 6,077 19,741 15,567 Total real estate services revenue 126,265 103,864 332,047 262,894 Properties revenue 11,350 3,364 23,388 5,345 Other revenue 2,640 2,251 7,356 6,043 Total revenue $ 140,255 $ 109,479 $ 362,791 $ 274,282 Other Considerations — The Company’s contracts with customers do not contain significant estimates or judgment. For both the real estate services and properties businesses, the Company's contracts with customers contain a single performance obligation that is recognized upon a transaction closing. The Company has utilized the practical expedient in ASC 606 and elected not to capitalize contract costs for contracts with customers with durations less than one year. The Company does not have significant remaining performance obligations or contract balances. Accrued Revenue and Allowance for Doubtful Accounts — The Company establishes an allowance for doubtful accounts after reviewing historical experience, age of accounts receivable balances and any other known conditions that may affect collectability. The majority of the Company’s transactions are processed through escrow and collectability is not a significant risk. Accrued revenue related to real estate services and properties transactions represents closed transactions for which the cash has not yet been received. Properties had no balances in these accounts as of September 30, 2018 . The following table presents the activity in the allowance for doubtful accounts for the period presented: Nine Months Ended September 30, 2018 Allowance for doubtful accounts: Balance, December 31, 2017 $ 160 Charges (28 ) Write-offs 25 Balance, September 30, 2018 $ 157 Accrued revenue as of September 30, 2018: Accrued revenue $ 13,411 Less: Allowance for doubtful accounts 157 Accrued revenue, net $ 13,254

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company accounts for certain assets and liabilities at fair value. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The current accounting guidance for fair value measurements defines a three-level valuation hierarchy for disclosures as follows: Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities. Level 2—Inputs other than quoted prices included within Level 1 that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. Level 3—Unobservable inputs that are supported by little or no market activity, requiring the Company to develop its own assumptions. The Company's interest rate lock commitments are measured at fair value on a recurring basis. The Company estimates the fair value of an interest rate lock commitment based on quoted investor prices, net of origination costs and fees and the probability that the mortgage loan will be purchased within the terms of the interest rate lock commitment. The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s financial instruments consist of Level 1, Level 2 and Level 3 assets and (liabilities). Level 1 assets include highly liquid money market funds, Level 2 assets and (liabilities) include forward sales commitments, and Level 3 assets and (liabilities) include interest rate lock commitments. As of September 30, 2018 , forward sales commitments and interest rate lock commitments were broken out between Other asset and Other payables, as well as interest rate lock commitments were reclassified to Level 3. A summary of assets and (liabilities) at September 30, 2018 and December 31, 2017, related to the Company's financial instruments, measured at fair value on a recurring basis, is set forth below: Fair Value Financial Instrument Balance sheet location September 30, 2018 December 31, 2017 Money market funds Cash and cash equivalents Level 1 $ 440,216 $ 177,235 Forward sales commitments Other current assets Level 2 71 9 Forward sales commitments Accrued liabilities Level 2 (6 ) (2 ) Interest rate lock commitments Other current assets Level 3 120 29 Interest rate lock commitments Accrued liabilities Level 3 (25 ) (4 ) The changes in the Level 3 financial instruments that are measured at fair value on a recurring basis were immaterial during the periods presented. See Note 15 for the carrying amount and estimated fair value of the Notes.

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment A summary of property and equipment at September 30, 2018 and December 31, 2017 is as follows: Useful Lives (Years) September 30, 2018 December 31, 2017 Leasehold improvements Shorter of lease term or economic life $ 17,610 $ 16,039 Website and software development costs 1-3 18,153 14,501 Computer and office equipment 3 2,678 2,192 Software 3 594 685 Furniture 7 3,636 3,039 Property and equipment, gross 42,671 36,456 Accumulated depreciation and amortization (19,310 ) (14,138 ) Property and equipment, net $ 23,361 $ 22,318 Depreciation and amortization expense for property and equipment amounted to $2,099 and $1,665 for the three months ended September 30, 2018 and 2017, respectively, and $5,757 and $4,960 for the nine months ended September 30, 2018 and 2017, respectively.

Acquired Intangible Assets

Acquired Intangible Assets	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Acquired Intangible Assets	Acquired Intangible Assets The following table presents details of the Company's intangible assets subject to amortization as of the dates presented: As of September 30, 2018 As of December 31, 2017 Useful Gross Accumulated Amortization Net Gross Accumulated Amortization Net Trade names 10 $ 1,040 $ (416 ) $ 624 $ 1,040 $ (338 ) $ 702 Developed technology 10 2,980 (1,192 ) 1,788 2,980 (968 ) 2,012 Customer relationships 10 860 (344 ) 516 860 (280 ) 580 $ 4,880 $ (1,952 ) $ 2,928 $ 4,880 $ (1,586 ) $ 3,294 Acquired intangible assets are amortized using the straight-line method over their estimated useful life, which approximates the expected use of these assets. Amortization expense amounted to $122 and $366 for the three and nine months ended September 30, 2018 and 2017, respectively. Amortization expense of $2,440 will be recognized over the next five years, or $488 per year.

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting In its operation of the business, the Company's management, including its chief operating decision maker, who is also the Chief Executive Officer, evaluates the performance of the Company’s operating segments based on revenue and gross profit. The Company does not analyze discrete segment balance sheet information related to long-term assets, all of which are located in the United States. All other financial information is presented on a consolidated basis. The Company has five operating segments and two reportable segments, real estate services and properties. The Company's reportable segments and other segments are described below: Real estate services Real estate services revenue is derived from commissions and fees charged on real estate services transactions closed by the Company or its partner agents. Properties Properties was a new reportable segment as of June 30, 2018 . Prior to June 30, 2018 , the properties segment results were included as part of the Company's other segment. Properties revenue is earned when the Company sells homes that it previously bought directly from homeowners. Other Other services revenue includes fees earned from mortgage banking services, title settlement services, Walk Score data services, and advertising. Included in other are all operating segments and revenue not otherwise included in reportable operating segments. Information on each of the reportable and other segments and reconciliation to consolidated net income (loss) is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Real estate services Revenue $ 126,265 $ 103,864 $ 332,047 $ 262,894 Cost of revenue 83,274 64,258 236,775 178,850 Gross profit $ 42,991 $ 39,606 $ 95,272 $ 84,044 Properties Revenue $ 11,350 $ 3,364 $ 23,388 $ 5,345 Cost of revenue 11,656 3,326 24,086 5,361 Gross profit $ (306 ) $ 38 $ (698 ) $ (16 ) Other Revenue $ 2,640 $ 2,251 $ 7,356 $ 6,043 Cost of revenue 3,020 2,582 8,715 7,422 Gross profit $ (380 ) $ (331 ) $ (1,359 ) $ (1,379 ) Consolidated Revenue $ 140,255 $ 109,479 $ 362,791 $ 274,282 Cost of revenue 97,950 70,166 269,576 191,633 Gross profit $ 42,305 $ 39,313 $ 93,215 $ 82,649 Operating expenses 39,016 29,066 124,643 96,252 Interest income 1,775 311 3,082 387 Interest expense (1,610 ) — (1,610 ) — Other income, net 21 — 200 13 Net income (loss) $ 3,475 $ 10,558 $ (29,756 ) $ (13,203 )

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock and Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Temporary Equity And Stockholder's Equity [Abstract]
Redeemable Convertible Preferred Stock and Stockholders' Equity	Redeemable Convertible Preferred Stock and Stockholders’ Equity Redeemable Convertible Preferred Stock —The Company's redeemable convertible preferred stock automatically converted into common stock at a rate of one -for-one on the closing of the Company's IPO on August 2, 2017. Therefore, no shares of redeemable convertible preferred stock were authorized, issued and outstanding as of September 30, 2018 . Please see Note 6 to the Company's consolidated financial statements in its Annual Report on Form 10-K for the fiscal year ended December 31, 2017 for a description of the terms of the redeemable convertible preferred stock. Accretion Expense —Accretion represents the increase in the redemption value of the Company’s redeemable convertible preferred stock. The recognized accretion expense related to the increase in the redemption value of the redeemable convertible preferred stock was reclassed upon the successful completion of the IPO, which occurred during 2017. The following table presents the accretion expense of the redeemable convertible preferred stock to its redemption value recorded within the consolidated statements of changes in redeemable convertible preferred stock and stockholders’ equity during the three and nine months ended September 30, 2017: Three Months Ended September 30, 2017 Nine Months Ended September 30, 2017 Series A-1 $ (1,119 ) $ (4,904 ) Series A-2 (28 ) (123 ) Series A-3 (2,349 ) (10,192 ) Series B (9,284 ) (40,336 ) Series C (8,530 ) (37,062 ) Series D (7,300 ) (31,717 ) Series E (2,948 ) (12,884 ) Series F (4,541 ) (20,184 ) Series G (4,125 ) (18,513 ) Total $ (40,224 ) $ (175,915 ) Common Stock —At September 30, 2018 and December 31, 2017 , the Company was authorized to issue 500,000,000 shares of common stock with a par value of $0.001 per share. The Company has reserved shares of common stock, on an as-converted basis, for future issuance as follows: September 30, 2018 December 31, 2017 Equity Incentive Plans: Stock options issued and outstanding 10,150,522 13,180,950 Restricted stock units outstanding 2,081,173 981,276 Shares available for future equity grants 6,214,739 7,026,071 Total 18,446,434 21,188,297 2017 Employee Stock Purchase Plan: Shares issued under employee stock purchase plan 187,076 — Shares available for future purchases under employee stock purchase plan 2,227,612 1,600,000 Total 2,414,688 1,600,000 Preferred Stock — As of September 30, 2018 and December 31, 2017, the Company had authorized 10,000,000 shares of preferred stock, par value $0.001 , of which no shares were issued and outstanding.

Stock-based Compensation

Stock-based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based Compensation	Stock-based Compensation 2017 Employee Stock Purchase Plan —The Company’s 2017 Employee Stock Purchase Plan (“2017 ESPP”) became effective on July 27, 2017 and enables eligible employees to purchase shares of the Company’s common stock at a discount. Purchases are accomplished through participation in discrete offering periods which last 6 months each, and begin every January 1 and July 1. The Company initially reserved 1,600,000 shares of common stock for issuance under the 2017 ESPP. The number of shares reserved for issuance under the 2017 ESPP will increase automatically on January 1 of each calendar year beginning after the first offering date and continuing through January 1, 2028 by the number of shares equal to the lesser of 1% of the total outstanding shares of the Company’s common stock as of the immediately preceding December 31 or an amount determined by the board of directors. On February 22, 2018, the board of directors determined to increase to the number of shares reserved for issuance under the 2017 ESPP by 814,688 shares. On each purchase date, participating employees purchase the Company’s common stock at a price per share equal to 85% of the lesser of (1) the fair market value of the Company’s common stock on the first trading day of the offering period, and (2) the fair market value of the Company’s common stock on the purchase date. During the three months ended September 30, 2018 , no shares of common stock were purchased under the 2017 ESPP. The fair value of common shares to be issued under the 2017 ESPP were calculated using the Black-Scholes-Merton option-pricing model with the following assumptions: For the Offering Period beginning July 1, 2018 Expected life 0.5 years Volatility 39.25% Risk-free interest rate 2.14% Dividend yield —% Weighted-average grant date fair value $5.94 2017 Equity Incentive Plan — The Company's 2017 Equity Incentive Plan ("2017 EIP") became effective on July 26, 2017, and provides for the issuance of incentive and nonqualified common stock options and restricted stock units to employees, directors, officers, and consultants of the Company. The Company initially reserved 7,898,159 shares of common stock for issuance under the 2017 EIP. The number of shares reserved for issuance under the 2017 EIP will increase automatically on January 1 of each calendar year beginning on January 1, 2018 and continuing through January 1, 2028, by the number of shares equal to the lesser of 5% of the total outstanding shares of the Company's common stock as of the immediately preceding December 31 or an amount determined by the board of directors. On December 22, 2017, the board of directors determined that there would be no increase to the number of shares reserved for issuance under the 2017 EIP on January 1, 2018. The term of each restricted stock unit under the plan shall be no more than 10 years and generally vest over a four -year period. The term of each option grant shall be no more than 10 years and generally vest over a four -year period. Amended and Restated 2004 Equity Incentive Plan -The Company granted options under its Amended and Restated 2004 Equity Incentive Plan, as amended (“2004 Plan”), until July 26, 2017, when the plan was terminated in connection with the Company’s IPO. Accordingly, no shares are available for future issuance under this plan. The 2004 Plan continues to govern outstanding equity awards granted thereunder. Options to Purchase Common Stock— The Company did not issue any options to purchase common stock during the three and nine months ended September 30, 2018 and the three months ended September 30, 2017. The fair value of the options issued under the Amended and Restated 2004 Equity Incentive Plan for the nine months ended September 30, 2017 were calculated using the Black-Scholes-Merton option-pricing model with the following assumptions: Nine Months Ended September 30, 2017 Expected life 7 years Volatility 37.88%-40.97% Risk-free interest rate 1.96%-2.26% Dividend yield —% Weighted-average grant date fair value 4.86 The following table presents information regarding options granted, exercised, forfeited, or canceled for the periods presented: Weighted- Average Exercise Price Weighted-Average Remaining Contractual Life (years) Outstanding at December 31, 2017 13,180,950 $ 6.30 7.02 $ 329,786 Options granted — — Options exercised (2,653,008) 5.17 Options forfeited (367,541) 9.45 Options canceled (9,879) 8.26 Outstanding at September 30, 2018 10,150,522 6.48 6.27 124,054 Options exercisable at September 30, 2018 7,750,226 $ 5.67 5.79 $ 100,976 The grant date fair value of options to purchase common stock is recorded as stock-based compensation over the vesting period. As of September 30, 2018 , there was $10,221 of total unrecognized compensation cost related to options to purchase common stock, which is expected to be recognized over a weighted-average period of 1.71 years . Restricted Stock Units— The following table summarizes activity for restricted stock units for the nine months ended September 30, 2018 : Restricted Stock Units Weighted Average Grant-Date Fair Value Unvested outstanding at December 31, 2017 981,276 $ 22.78 Granted 1,400,212 21.17 Vested (127,746 ) 22.57 Forfeited or canceled (172,569 ) 21.86 Unvested outstanding at September 30, 2018 2,081,173 $ 21.79 The grant date fair value of restricted stock units is recorded as stock-based compensation over the vesting period. As of September 30, 2018 , there was $41,148 of total unrecognized compensation cost related to restricted stock units, which is expected to be recognized over a weighted-average period of 3.28 years . During the three months ended September 30, 2018 , the Company granted 8,913 restricted stock units subject to performance conditions at 100% of the target level. As of September 30, 2018, there were outstanding 143,890 restricted stock units subject to performance conditions (the "2018 Performance RSUs") at 100% of the target level. Depending on the Company's achievement of the performance conditions, the actual amount of shares of common stock issuable upon vesting of the 2018 Performance RSUs will range from 0% to 200% of the target amount of restricted stock units. For each recipient of the 2018 Performance RSUs, the award will vest, subject to the recipient continuing to provide service to the Company, upon the Company's board of directors, or its compensation committee, certifying that the Company achieved certain financial targets for the three -year period from January 1, 2018 to December 31, 2020. Share-based compensation expense for 2018 Performance RSUs will be recognized when it is probable that the performance conditions will be achieved. As of September 30, 2018 , $379 of share-based compensation expense was recognized for the 2018 Performance RSUs. Compensation Cost —The following table presents detail of stock-based compensation, net of the amount capitalized in internally developed software, included in the Company’s condensed consolidated statements of operations for the periods indicated below Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Cost of revenue $ 1,370 $ 715 $ 4,061 $ 2,129 Technology and development 2,135 819 5,334 2,301 Marketing 155 121 431 362 General and administrative 1,838 1,054 4,646 3,236 Total stock-based compensation $ 5,498 $ 2,709 $ 14,472 $ 8,028

Net Income (Loss) per Share Att

Net Income (Loss) per Share Attributable to Common Stock	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Income (Loss) per Share Attributable to Common Stock	Net Income (Loss) per Share Attributable to Common Stock Net income (loss) per share attributable to common stock is computed by dividing the net income (loss) attributable to common stock by the weighted-average number of common shares outstanding. The Company has outstanding stock options, restricted stock units, employee stock purchase plan shares, Notes, and previously had redeemable convertible preferred stock, which are considered in the calculation of diluted net income (loss) attributable to common stock per share whenever doing so would be dilutive. The Company calculates basic and diluted net income (loss) per share attributable to common stock in conformity with the two-class method required for companies with participating securities. The Company considers all series of redeemable convertible preferred stock to be participating securities. Under the two-class method, net income (loss) attributable to common stock is not allocated to the redeemable convertible preferred stock as the holders of redeemable convertible preferred stock do not have a contractual obligation to share in losses. Upon the conversion of the redeemable convertible preferred stock to common stock on the date of the IPO, or August 2, 2017, the Company only had one class of participating security, common stock. Diluted net income (loss) per share attributable to common stock is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period. The following table sets forth the calculation of basic and diluted net income (loss) per share attributable to common stock during the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Numerator: Net income (loss) $ 3,475 $ 10,558 $ (29,756 ) $ (13,203 ) Accretion of preferred stock — (40,224 ) — (175,915 ) Net income (loss) attributable to common stock - basic and diluted $ 3,475 $ (29,666 ) $ (29,756 ) $ (189,118 ) Denominator: Weighted average shares: Basic 87,743,223 58,868,903 84,327,266 29,678,082 Dilutive shares from stock plans 6,899,240 — — — Diluted 94,642,463 58,868,903 84,327,266 29,678,082 Net income (loss) per share: Net income (loss) per share attributable to common stock - basic $ 0.04 $ (0.50 ) $ (0.35 ) $ (6.37 ) Net income (loss) per share attributable to common stock - diluted $ 0.04 $ (0.50 ) $ (0.35 ) $ (6.37 ) The following outstanding shares of common stock equivalents as of September 30, 2018 and 2017 were excluded from the computation of the diluted net income (loss) per share attributable to common stock for the periods presented because their effect would have been anti-dilutive: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Redeemable convertible preferred stock — 55,422,002 — 55,422,002 Options to purchase common stock — 13,298,339 10,150,522 13,298,339 Restricted stock units 238,668 — 2,081,173 — Total 238,668 68,720,341 12,231,695 68,720,341 The Company considered the impact of the Notes on its diluted net income per share for the three months ended September 30, 2018 based on the treasury stock method as the Company has the ability, and intends, to settle any conversions of the Notes solely in cash. The treasury stock method requires that the dilutive effect of common stock issuable upon conversion of the Notes be computed in the periods in which it reports net income. For the three months ended September 30, 2018, there was no dilutive effect from the Notes.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act incorporates broad and complex changes to the U.S. tax code. The main provision of the Tax Act that is applicable to the Company is the reduction of a maximum federal tax rate of 35% to a flat tax rate of 21%, effective January 1, 2018. The Company incorporated the change in federal tax rates in its annual tax provision for the period ended December 31, 2017. The net impact to the Company’s tax expense was $0 . As of December 31, 2017, the Company completed and recorded the adjustments necessary under Staff Accounting Bulletin No. 118 related to the Tax Act. The Company’s effective tax rate for the three and nine months ended September 30, 2018 and 2017 was 0% as a result of the Company recording a full valuation allowance against the deferred tax assets. In determining the realizability of the net U.S. federal and state deferred tax assets, the Company considers numerous factors including historical profitability, estimated future taxable income, prudent and feasible tax planning strategies and the industry in which it operates. Management reassesses the realization of the deferred tax assets each reporting period, which resulted in a valuation allowance against the full amount of the Company’s U.S. deferred tax assets for the three and nine month ended September 30, 2018 and 2017. To the extent that the financial results of the U.S. operations improve in the future and the deferred tax assets become realizable, the Company will reduce the valuation allowance through earnings. Under Section 382 of the Internal Revenue Code of 1986, as amended, substantial changes in the Company's ownership may limit the amount of net operating loss carryforwards that could be utilized annually in the future to offset taxable income. Any such annual limitation may significantly reduce the utilization of the net operating losses before they expire. A Section 382 limitation study performed as of March 31, 2017 determined there was an ownership change in 2006 and $1,538 of the 2006 net operating loss is unavailable. Net operating loss carryforwards are available to offset federal taxable income and begin to expire in 2025. As of December 31, 2017 the Company has accumulated approximately $87,071 of federal tax losses, and approximately $4,231 (tax effected) of state losses. The Company’s material income tax jurisdiction is the United States (federal). As a result of net operating loss carryforwards, the Company is subject to audit for tax years 2005 and forward for federal purposes. There are tax years which remain subject to examination in various other jurisdictions that are not material to the Company’s financial statements.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings — From time to time the Company is involved in litigation, claims and other proceedings arising in the ordinary course of business. This litigation and other proceedings may include, but are not limited to, actions relating to employment law, independent contractor misclassification, intellectual property, commercial or contractual claims, brokerage or real estate disputes, claims related to the Real Estate Settlement Procedures Act of 1974, the Fair Housing Act of 1968, or other consumer protection statutes, claims related to real or perceived conflicts of interest or failure to satisfy duties to our customers, real estate disputes like the failure to disclose property defects, commission disputes, and vicarious liability based upon conduct of individuals or entities outside of the Company's control, including partner agents and third-party contractor agents. Litigation and other disputes are inherently unpredictable and subject to substantial uncertainties and unfavorable resolutions could occur. Often these cases raise complex factual and legal issues, which are subject to risks and uncertainties and could require significant management time and resources. Facility Leases and Other Commitments —The Company leases its office space under noncancelable operating leases with terms ranging from one to 11 years. Generally, the leases require a fixed minimum rent with contractual minimum rent increases over the lease term, and certain leases include escalation provisions. Rent expense totaled $2,015 and $1,705 for the three months ended September 30, 2018 and 2017, respectively, and $5,859 and $6,030 for the nine months ended September 30, 2018 and 2017, respectively. Other commitments relate to homes that the Company is under contract to purchase through RedfinNow but that have not closed, and network infrastructure for the Company’s data operations. Future minimum payments due under these agreements as of September 30, 2018 are as follows: September 30, 2018 Facility Leases Other Commitments 2018 $ 2,256 $ 4,556 2019 9,940 2,386 2020 9,668 218 2021 9,040 83 2022 and thereafter 34,922 0 Total minimum lease payments $ 65,826 $ 7,243 Mortgage Warehouse and Master Repurchase Agreements — In December 2016, Redfin Mortgage, LLC ("Redfin Mortgage") entered into a Mortgage Warehouse Agreement with Texas Capital Bank, National Association (“Texas Capital”), which was amended and restated in December 2017. In June 2017, Redfin Mortgage entered into a Master Repurchase Agreement, which was amended in September 2018, with Western Alliance Bank. Pursuant to each of the Mortgage Warehouse Agreement and Master Repurchase Agreement, Texas Capital and Western Alliance Bank, respectively, agree to fund loans originated by Redfin Mortgage, in its discretion, up to $10,000 and to take a security interest in such loans. The per annum interest rate payable to Texas Capital is a fixed rate equal to the rate of interest accruing on the outstanding principal balance of the loan, minus 0.5% , or 3.0% , whichever is higher. The per annum interest rate payable to Western Alliance Bank is a fixed rate equal to the LIBOR rate plus 2.75% , or 3.50% , whichever is higher. For each loan in which Texas Capital elects to purchase a participation interest, it will acquire an undivided 97% participation interest, by paying as the purchase price an amount equal to the participation interest multiplied by the principal balance of the loan. For each loan in which Western Alliance Bank elects to purchase, it will acquire an undivided 98% participation interest, by paying as the purchase price an amount equal to the participation interest multiplied by the principal balance of the loan. If a loan is not sold to a correspondent lender, Texas Capital and Western Alliance Bank's participation interests in the loans are to be repurchased in whole or in part by Redfin Mortgage. The Company has guaranteed Redfin Mortgage’s obligations under the Mortgage Warehouse and Master Repurchase Agreements. The Mortgage Warehouse Agreement and Master Repurchase Agreement each requires Redfin Mortgage to maintain certain financial covenants and to provide periodic financial and compliance reports. Redfin Mortgage failed to satisfy certain financial covenants contained in each of the Mortgage Warehouse Agreement and Master Repurchase Agreement as of September 30, 2018 , but neither Texas Capital nor Western Alliance Bank, respectively, has enforced its remedies under the agreement. As of September 30, 2018 there was $5,791 outstanding under the Mortgage Warehouse Agreement and $0 outstanding on the Master Repurchase Agreement. As of December 31, 2017 there was $833 outstanding under the Mortgage Warehouse Agreement and $1,184 outstanding on the Master Repurchase Agreement. The Mortgage Warehouse Agreement expires on March 22, 2019 and the Master Repurchase Agreement expires on June 15, 2019.

Accrued Liabilities

Accrued Liabilities	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued Liabilities The following table presents the detail of accrued liabilities as of the dates presented: September 30, 2018 December 31, 2017 Accrued compensation and benefits $ 29,370 $ 19,543 Legal fees and settlements 270 2,230 Miscellaneous accrued liabilities 7,892 4,832 Total accrued liabilities: $ 37,532 $ 26,605

Other Payables

Other Payables	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Other Payables	Other Payables Other payables consists primarily of customer deposits for cash held in escrow on behalf of real estate buyers using the Company's title and settlement services. Since the Company does not have rights to the cash the customer deposits are recorded as a liability with a corresponding asset in the same amount recorded within restricted cash. The following table presents the detail of other payables as of the dates presented: September 30, 2018 December 31, 2017 Customer deposits $ 11,773 $ 4,068 Miscellaneous payables 394 — Total other payables: $ 12,167 $ 4,068

Retirement Plan

Retirement Plan	9 Months Ended
	Sep. 30, 2018
Retirement Benefits [Abstract]
Retirement Plan	Retirement Plan The Company adopted a 401(k) profit sharing plan effective January 2005. The plan covers eligible employees as of their hire date. The 401(k) component of the plan allows employees to elect to defer from 1% to 100% of their eligible compensation up to the federal limit per year. Company-matching and profit-sharing contributions are discretionary and are determined annually by Company management and approved by the board of directors. No matching or profit-sharing contributions were declared for the three and nine months ended September 30, 2018 and 2017.

Convertible Senior Notes

Convertible Senior Notes	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Convertible Senior Notes	Convertible Senior Notes On July 23, 2018, the Company issued $143,750 aggregate principal amount of Notes, from which it received $138,953 in net proceeds after deducting the underwriting discount and other issuance costs. The Notes are senior, unsecured obligations of Redfin, and bear interest at a fixed rate of 1.75% per year, payable semi-annually in arrears on January 15 and July 15. The Notes mature on July 15, 2023, unless earlier repurchased, redeemed or converted. Prior to April 15, 2023, the Notes are convertible at the option of holders during certain periods, upon satisfaction of certain conditions. Thereafter, the Notes are convertible at any time until the close of business on the second scheduled trading day immediately preceding the maturity date. Redfin may redeem for cash all or any portion of the notes, at its option, on or after July 20, 2021, upon satisfaction of certain conditions at a redemption price equal to 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid interest. Redfin will settle conversions of the Notes by paying or delivering, as the case may be, cash, shares of its common stock, or a combination of cash and shares of its common stock, at its election. The Company has the ability, and intends, to settle any conversions solely in cash. Holders of the Notes have the right to require Redfin to repurchase for cash all or a portion of their Notes at 100% of their principal amount, plus any accrued and unpaid interest, upon the occurrence of a fundamental change (as defined in the indenture relating to the Notes). Redfin is required to increase the conversion rate for holders who convert their notes in connection with certain fundamental changes occurring prior to the maturity date or following Redfin’s issuance of a notice of redemption. The initial conversion rate of the Notes is 32.7332 shares of common stock per $1,000 principal amount of Notes, equivalent to an initial conversion price of approximately $30.55 per share of common stock. The initial conversion price represents a premium of approximately 30% to the $23.50 per share public offering price for the common stock offering. In accounting for the issuance of the Notes, the value was allocated to liability and equity components. The carrying amount of the liability component was determined by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was calculated by deducting the fair value of the liability component from the principal amount of the Notes as a whole. The difference between the principal amount of the Notes and the liability component (the debt discount) is amortized to interest expense in the condensed consolidated statements of operations using the effective interest method over the term of the Notes. The equity component of the Notes is included in additional paid-in capital in the condensed consolidated balance sheets and is not remeasured as long as it continues to meet the conditions for equity classification. The Company incurred total debt issuance costs of $4,797 , of which approximately $3,832 was allocated to the Notes and approximately $965 was allocated to additional paid-in capital. The Notes consisted of the following: As of September 30, 2018 Liability: Principal $ 143,750 Less: debt discount, net of amortization (27,919 ) Less: debt issuance costs, net of amortization (3,701 ) Net carrying amount of the Notes $ 112,130 Stockholders' equity: Allocated value of the conversion feature $ 28,916 Less: debt issuance costs (965 ) Additional paid-in capital $ 27,951 The following table sets forth total interest expense recognized related to the Notes for the period presented: Three Months Ended September 30, 2018 Amortization of debt discount $ 997 Amortization of debt issuance costs 131 Total amortization of debt issuance costs and accretion of equity portion 1,128 Contractual interest expense 482 Total interest expense related to the Notes $ 1,610 Effective interest rate of the liability component 7.10 % The total estimated fair value of the Notes as of September 30, 2018 was approximately $129,195 based on the closing trading price of the Notes on last day of trading for the period. The fair value has been classified as Level 2 within the fair value hierarchy given the limited trading activity of the Notes.

Description of Business and S_2

Description of Business and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation — The consolidated financial statements and accompanying notes have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”). The Company had no components of other comprehensive income (loss) during any of the periods presented, as such, a consolidated statement of comprehensive income (loss) is not presented. All amounts are presented in thousands, except share and per share data. The unaudited condensed consolidated interim financial statements, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary to present fairly the Company's financial position as of September 30, 2018 , the Company's results of operations for the three and nine months ended September 30, 2018 and 2017, and the Company's cash flows for the nine months ended September 30, 2018 and 2017. The results for the three and nine months ended September 30, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any interim period or for any other future year.
Principles of Consolidation	Principles of Consolidation —The unaudited condensed consolidated interim financial statements include the accounts of Redfin and its wholly owned subsidiaries. Intercompany transactions and balances have been eliminated.
Use of Estimates	Use of Estimates — The preparation of consolidated financial statements, in conformity with GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and results of operations during the respective periods. The Company’s more significant estimates include, but are not limited to, valuation of deferred income taxes, stock-based compensation, net realizable value of inventory, prior to its conversion on August 2, 2017 the fair value of common stock and redeemable convertible preferred stock, capitalization of website development costs, recoverability of intangible assets with finite lives, fair value of reporting units for purposes of evaluating goodwill for impairment, and the fair value of the convertible feature related to the Notes (see Note 15). The amounts ultimately realized from the affected assets or ultimately recognized as liabilities will depend on, among other factors, general business conditions and could differ materially in the near term from the carrying amounts reflected in the consolidated financial statements.
Recently Adopted and Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements — In May 2014, the Financial Accounting Standards Board ("FASB") issued a new Accounting Standard Update ("ASU") 2014-09, Revenue from Contracts with Customers (Topic 606) . This guidance provides that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance also requires more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The Company adopted ASU 2014-09 and its related amendments (collectively known as ASC 606) effective on January 1, 2018, using the modified retrospective adoption methodology. Real estate services, properties and other revenue contain single performance obligations and the Company believes the timing of the satisfaction of the performance obligations, triggering the recognition of revenue, did not differ from the Company's timing for recognizing revenue prior to adopting this pronouncement. Further description of the impact of this pronouncement is included in Note 2: Revenue from Contracts with Customers. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230). This guidance impacts the classification of certain cash receipts and cash payments in the statement of cash flows. The new standard made eight targeted changes to how cash receipts and cash payments are presented and classified in the statement of cash flows. The Company adopted the new standard on a retrospective basis on January 1, 2018. The adoption of this standard had no impact on the Company’s statement of cash flows. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash . This guidance impacts the classification and presentation of changes in restricted cash on the statement of cash flows. This guidance is effective for interim and annual reporting periods beginning after December 15, 2017, and early adoption is permitted. The adoption of this guidance requires a retrospective transition method to each period presented. The Company early adopted this guidance on October 1, 2017. Upon adoption, the following balances were reclassified: restricted cash to the reconciliation of change in cash, cash equivalents and restricted cash, and other payables related to cash held in escrow on behalf of customers to financing activities. In the Company’s capacity as fiduciary, the cash receipt is a function of providing the customer with a service (title). Therefore, the escrow funds payable are akin to a repayment of debt, a financing activity, whereby the Company in its role as fiduciary is temporarily holding cash in its restricted accounts on behalf of its customers and subsequently releases the cash to settle the customers' contractual obligation. This reclassification will maintain an accurate reflection of the Company's cash flows from operating and financing activities. The reconciliation of amounts previously reported to the revised amounts upon adoption are as follows: Nine Months Ended September 30, 2017 Previously reported Adjustments As revised Cash provided by operating activities $ 10,551 $ 222 $ 10,773 Cash provided by financing activities $ 147,863 $ 6,065 $ 153,928 Net change in cash, cash equivalents, and restricted cash (1) $ 148,406 $ 6,287 $ 154,693 (1) Previously titled: net change in cash and cash equivalents Recently Issued Accounting Pronouncements — In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) . This standard requires the recognition of a right-of-use asset and lease liability on the balance sheet for all leases. This standard also requires more detailed disclosures to enable users of financial statements to understand the amount, timing, and uncertainty of cash flows arising from leases. This guidance is effective for interim and annual reporting periods beginning after December 15, 2018. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842) providing an optional alternative transition method to the modified retrospective approach whereby under this optional transition method an entity initially applies the new leases standard at the adoption date and recognizes a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In addition, this ASU provides a practical expedient, by class of underlying asset, to not separate non-lease components from the associated lease and instead account for the lease as a single component if both the timing and pattern of transfer of the non-lease component(s) are the same, and if the lease would be classified as an operating lease. These amendments have the same effective date as ASU 2016-02. Early adoption is permitted for both ASU 2016-02 and 2018-11. The Company plans to elect the optional transition method on the adoption date of January 1, 2019. The Company is in the process of evaluating the impact of adoption of the ASU on its consolidated financial statements, including implementing changes to its systems, processes, and internal controls. It is believed the most significant change will relate to the recognition of right-of-use assets and lease liabilities on the Company’s balance sheet for real estate leases that are currently accounted for as operating leases, as well as the accompanying disclosures. The Company is unable to estimate the impact at this time but believes it will be material. In August 2018, the Securities and Exchange Commission (the "SEC") adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification , amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. This final rule became effective on November 5, 2018, but the staff of the SEC provided relief on the effective date of the rule with respect to the analysis of stockholders' equity until the Company's Form 10-Q for its fiscal quarter ending March 31, 2019. The Company is in the process of evaluating the impact of the final rule on its condensed consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) , which modifies the disclosures on fair value measurements by removing the requirement to disclose the amount and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy and the policy for timing of such transfers. The ASU expands the disclosure requirements for Level 3 fair value measurements, primarily focused on changes in unrealized gains and losses included in other comprehensive income. The ASU is effective for public entities for fiscal years beginning after December 15, 2019, with early adoption permitted. The Company has not yet completed its assessment of the impact of the new standard on the Company’s Consolidated Financial Statements. In August 2018, the FASB issued authoritative guidance under ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software: Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract . The ASU requires implementation costs incurred by customers in cloud computing arrangements (i.e., hosting arrangements) to be capitalized under the same premises of authoritative guidance for internal-use software, and deferred over the noncancellable term of the cloud computing arrangements plus any option renewal periods that are reasonably certain to be exercised by the customer or for which the exercise is controlled by the service provider. The ASU is effective in the first quarter of fiscal 2021. The Company is currently in the process of evaluating the impact of the final rule on its consolidated financial statements.
Fair Value of Financial Instruments	Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The current accounting guidance for fair value measurements defines a three-level valuation hierarchy for disclosures as follows: Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities. Level 2—Inputs other than quoted prices included within Level 1 that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. Level 3—Unobservable inputs that are supported by little or no market activity, requiring the Company to develop its own assumptions. The Company's interest rate lock commitments are measured at fair value on a recurring basis. The Company estimates the fair value of an interest rate lock commitment based on quoted investor prices, net of origination costs and fees and the probability that the mortgage loan will be purchased within the terms of the interest rate lock commitment. The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company’s financial instruments consist of Level 1, Level 2 and Level 3 assets and (liabilities). Level 1 assets include highly liquid money market funds, Level 2 assets and (liabilities) include forward sales commitments, and Level 3 assets and (liabilities) include interest rate lock commitments.

Description of Business and S_3

Description of Business and Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The reconciliation of amounts previously reported to the revised amounts upon adoption are as follows: Nine Months Ended September 30, 2017 Previously reported Adjustments As revised Cash provided by operating activities $ 10,551 $ 222 $ 10,773 Cash provided by financing activities $ 147,863 $ 6,065 $ 153,928 Net change in cash, cash equivalents, and restricted cash (1) $ 148,406 $ 6,287 $ 154,693 (1) Previously titled: net change in cash and cash equivalents

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The Company's revenue from contracts with customers for the various revenue categories is as follows: Three Months Ended Nine Months Ended 2018 2017 2018 2017 Real estate services Brokerage revenue $ 118,809 $ 97,787 $ 312,306 $ 247,327 Partner revenue 7,456 6,077 19,741 15,567 Total real estate services revenue 126,265 103,864 332,047 262,894 Properties revenue 11,350 3,364 23,388 5,345 Other revenue 2,640 2,251 7,356 6,043 Total revenue $ 140,255 $ 109,479 $ 362,791 $ 274,282
Contract with Customer, Asset and Liability	The following table presents the activity in the allowance for doubtful accounts for the period presented: Nine Months Ended September 30, 2018 Allowance for doubtful accounts: Balance, December 31, 2017 $ 160 Charges (28 ) Write-offs 25 Balance, September 30, 2018 $ 157 Accrued revenue as of September 30, 2018: Accrued revenue $ 13,411 Less: Allowance for doubtful accounts 157 Accrued revenue, net $ 13,254

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Assets, Liabilities, and Equity Measured at Fair Value on a Recurring Basis	A summary of assets and (liabilities) at September 30, 2018 and December 31, 2017, related to the Company's financial instruments, measured at fair value on a recurring basis, is set forth below: Fair Value Financial Instrument Balance sheet location September 30, 2018 December 31, 2017 Money market funds Cash and cash equivalents Level 1 $ 440,216 $ 177,235 Forward sales commitments Other current assets Level 2 71 9 Forward sales commitments Accrued liabilities Level 2 (6 ) (2 ) Interest rate lock commitments Other current assets Level 3 120 29 Interest rate lock commitments Accrued liabilities Level 3 (25 ) (4 )

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment	A summary of property and equipment at September 30, 2018 and December 31, 2017 is as follows: Useful Lives (Years) September 30, 2018 December 31, 2017 Leasehold improvements Shorter of lease term or economic life $ 17,610 $ 16,039 Website and software development costs 1-3 18,153 14,501 Computer and office equipment 3 2,678 2,192 Software 3 594 685 Furniture 7 3,636 3,039 Property and equipment, gross 42,671 36,456 Accumulated depreciation and amortization (19,310 ) (14,138 ) Property and equipment, net $ 23,361 $ 22,318

Acquired Intangible Assets (Tab

Acquired Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	The following table presents details of the Company's intangible assets subject to amortization as of the dates presented: As of September 30, 2018 As of December 31, 2017 Useful Gross Accumulated Amortization Net Gross Accumulated Amortization Net Trade names 10 $ 1,040 $ (416 ) $ 624 $ 1,040 $ (338 ) $ 702 Developed technology 10 2,980 (1,192 ) 1,788 2,980 (968 ) 2,012 Customer relationships 10 860 (344 ) 516 860 (280 ) 580 $ 4,880 $ (1,952 ) $ 2,928 $ 4,880 $ (1,586 ) $ 3,294

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Reconciliation of Operating Profit (Loss) from Segments to Consolidated	Information on each of the reportable and other segments and reconciliation to consolidated net income (loss) is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Real estate services Revenue $ 126,265 $ 103,864 $ 332,047 $ 262,894 Cost of revenue 83,274 64,258 236,775 178,850 Gross profit $ 42,991 $ 39,606 $ 95,272 $ 84,044 Properties Revenue $ 11,350 $ 3,364 $ 23,388 $ 5,345 Cost of revenue 11,656 3,326 24,086 5,361 Gross profit $ (306 ) $ 38 $ (698 ) $ (16 ) Other Revenue $ 2,640 $ 2,251 $ 7,356 $ 6,043 Cost of revenue 3,020 2,582 8,715 7,422 Gross profit $ (380 ) $ (331 ) $ (1,359 ) $ (1,379 ) Consolidated Revenue $ 140,255 $ 109,479 $ 362,791 $ 274,282 Cost of revenue 97,950 70,166 269,576 191,633 Gross profit $ 42,305 $ 39,313 $ 93,215 $ 82,649 Operating expenses 39,016 29,066 124,643 96,252 Interest income 1,775 311 3,082 387 Interest expense (1,610 ) — (1,610 ) — Other income, net 21 — 200 13 Net income (loss) $ 3,475 $ 10,558 $ (29,756 ) $ (13,203 )

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock and Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Temporary Equity And Stockholder's Equity [Abstract]
Temporary Equity	The following table presents the accretion expense of the redeemable convertible preferred stock to its redemption value recorded within the consolidated statements of changes in redeemable convertible preferred stock and stockholders’ equity during the three and nine months ended September 30, 2017: Three Months Ended September 30, 2017 Nine Months Ended September 30, 2017 Series A-1 $ (1,119 ) $ (4,904 ) Series A-2 (28 ) (123 ) Series A-3 (2,349 ) (10,192 ) Series B (9,284 ) (40,336 ) Series C (8,530 ) (37,062 ) Series D (7,300 ) (31,717 ) Series E (2,948 ) (12,884 ) Series F (4,541 ) (20,184 ) Series G (4,125 ) (18,513 ) Total $ (40,224 ) $ (175,915 )
Schedule of Reserved Shares of Common Stock	The Company has reserved shares of common stock, on an as-converted basis, for future issuance as follows: September 30, 2018 December 31, 2017 Equity Incentive Plans: Stock options issued and outstanding 10,150,522 13,180,950 Restricted stock units outstanding 2,081,173 981,276 Shares available for future equity grants 6,214,739 7,026,071 Total 18,446,434 21,188,297 2017 Employee Stock Purchase Plan: Shares issued under employee stock purchase plan 187,076 — Shares available for future purchases under employee stock purchase plan 2,227,612 1,600,000 Total 2,414,688 1,600,000

Stock-based Compensation (Table

Stock-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Value Assumptions	The fair value of the options issued under the Amended and Restated 2004 Equity Incentive Plan for the nine months ended September 30, 2017 were calculated using the Black-Scholes-Merton option-pricing model with the following assumptions: Nine Months Ended September 30, 2017 Expected life 7 years Volatility 37.88%-40.97% Risk-free interest rate 1.96%-2.26% Dividend yield —% Weighted-average grant date fair value 4.86 The fair value of common shares to be issued under the 2017 ESPP were calculated using the Black-Scholes-Merton option-pricing model with the following assumptions: For the Offering Period beginning July 1, 2018 Expected life 0.5 years Volatility 39.25% Risk-free interest rate 2.14% Dividend yield —% Weighted-average grant date fair value $5.94
Schedule of Stock Option Activity	The following table presents information regarding options granted, exercised, forfeited, or canceled for the periods presented: Weighted- Average Exercise Price Weighted-Average Remaining Contractual Life (years) Outstanding at December 31, 2017 13,180,950 $ 6.30 7.02 $ 329,786 Options granted — — Options exercised (2,653,008) 5.17 Options forfeited (367,541) 9.45 Options canceled (9,879) 8.26 Outstanding at September 30, 2018 10,150,522 6.48 6.27 124,054 Options exercisable at September 30, 2018 7,750,226 $ 5.67 5.79 $ 100,976
Schedule of Nonvested Restricted Stock Units Activity	The following table summarizes activity for restricted stock units for the nine months ended September 30, 2018 : Restricted Stock Units Weighted Average Grant-Date Fair Value Unvested outstanding at December 31, 2017 981,276 $ 22.78 Granted 1,400,212 21.17 Vested (127,746 ) 22.57 Forfeited or canceled (172,569 ) 21.86 Unvested outstanding at September 30, 2018 2,081,173 $ 21.79
Schedule of Allocation of Share-based Compensation Costs	The following table presents detail of stock-based compensation, net of the amount capitalized in internally developed software, included in the Company’s condensed consolidated statements of operations for the periods indicated below Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Cost of revenue $ 1,370 $ 715 $ 4,061 $ 2,129 Technology and development 2,135 819 5,334 2,301 Marketing 155 121 431 362 General and administrative 1,838 1,054 4,646 3,236 Total stock-based compensation $ 5,498 $ 2,709 $ 14,472 $ 8,028

Net Income (Loss) per Share A_2

Net Income (Loss) per Share Attributable to Common Stock (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Earnings Per Share	The following table sets forth the calculation of basic and diluted net income (loss) per share attributable to common stock during the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Numerator: Net income (loss) $ 3,475 $ 10,558 $ (29,756 ) $ (13,203 ) Accretion of preferred stock — (40,224 ) — (175,915 ) Net income (loss) attributable to common stock - basic and diluted $ 3,475 $ (29,666 ) $ (29,756 ) $ (189,118 ) Denominator: Weighted average shares: Basic 87,743,223 58,868,903 84,327,266 29,678,082 Dilutive shares from stock plans 6,899,240 — — — Diluted 94,642,463 58,868,903 84,327,266 29,678,082 Net income (loss) per share: Net income (loss) per share attributable to common stock - basic $ 0.04 $ (0.50 ) $ (0.35 ) $ (6.37 ) Net income (loss) per share attributable to common stock - diluted $ 0.04 $ (0.50 ) $ (0.35 ) $ (6.37 )
Summary of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following outstanding shares of common stock equivalents as of September 30, 2018 and 2017 were excluded from the computation of the diluted net income (loss) per share attributable to common stock for the periods presented because their effect would have been anti-dilutive: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Redeemable convertible preferred stock — 55,422,002 — 55,422,002 Options to purchase common stock — 13,298,339 10,150,522 13,298,339 Restricted stock units 238,668 — 2,081,173 — Total 238,668 68,720,341 12,231,695 68,720,341

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Payments	Future minimum payments due under these agreements as of September 30, 2018 are as follows: September 30, 2018 Facility Leases Other Commitments 2018 $ 2,256 $ 4,556 2019 9,940 2,386 2020 9,668 218 2021 9,040 83 2022 and thereafter 34,922 0 Total minimum lease payments $ 65,826 $ 7,243

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	The following table presents the detail of accrued liabilities as of the dates presented: September 30, 2018 December 31, 2017 Accrued compensation and benefits $ 29,370 $ 19,543 Legal fees and settlements 270 2,230 Miscellaneous accrued liabilities 7,892 4,832 Total accrued liabilities: $ 37,532 $ 26,605

Other Payables (Tables)

Other Payables (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Schedule of Other Payables	The following table presents the detail of other payables as of the dates presented: September 30, 2018 December 31, 2017 Customer deposits $ 11,773 $ 4,068 Miscellaneous payables 394 — Total other payables: $ 12,167 $ 4,068

Convertible Senior Notes (Table

Convertible Senior Notes (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The Notes consisted of the following: As of September 30, 2018 Liability: Principal $ 143,750 Less: debt discount, net of amortization (27,919 ) Less: debt issuance costs, net of amortization (3,701 ) Net carrying amount of the Notes $ 112,130 Stockholders' equity: Allocated value of the conversion feature $ 28,916 Less: debt issuance costs (965 ) Additional paid-in capital $ 27,951 The following table sets forth total interest expense recognized related to the Notes for the period presented: Three Months Ended September 30, 2018 Amortization of debt discount $ 997 Amortization of debt issuance costs 131 Total amortization of debt issuance costs and accretion of equity portion 1,128 Contractual interest expense 482 Total interest expense related to the Notes $ 1,610 Effective interest rate of the liability component 7.10 %

Description of Business and S_4

Description of Business and Summary of Significant Accounting Policies - Narrative (Details) $ / shares in Units, $ in Thousands	Jul. 23, 2018USD ($)$ / sharesshares	Aug. 02, 2017USD ($)$ / sharesshares	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock issued upon conversion (in shares) | shares		55,422,002
Conversion basis		1
Initial public offering costs					$ 3,708
Proceeds from issuance of convertible senior notes			$ 138,953	$ 0
Proceeds from issuance of convertible debt, net of underwriting discounts	$ 138,953
Issuance costs of common stock and debt offerings			862
Accumulated deficit			158,759		129,003
Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Initial public offering costs					$ 3,708
IPO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shares sold in offering (in shares) | shares		10,615,650
Offering price (in dollars per share) | $ / shares		$ 15
Net proceeds from stock offering		$ 144,380
IPO | Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Initial public offering costs			$ 3,708
Public Offerings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shares sold in offering (in shares) | shares	4,836,336
Offering price (in dollars per share) | $ / shares	$ 23.50
Net proceeds from stock offering	$ 107,593
Over-Allotment Option
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shares sold in offering (in shares) | shares	630,826	1,384,650
1.75% Convertible Senior Notes due 2023
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Proceeds from issuance of convertible senior notes	$ 143,750
Stated interest rate	1.75%
Proceeds from issuance of convertible debt, net of underwriting discounts	$ 138,953
1.75% Convertible Senior Notes due 2023 | Over-Allotment Option
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Proceeds from issuance of convertible senior notes	$ 18,750

Description of Business and S_5

Description of Business and Summary of Significant Accounting Policies - Adjustments for New Accounting Policies (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash provided by operating activities	$ (20,808)	$ 10,773
Cash provided by financing activities	274,614	153,928
Net change in cash, cash equivalents, and restricted cash	$ 248,278	154,693
Previously reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash provided by operating activities		10,551
Cash provided by financing activities		147,863
Net change in cash, cash equivalents, and restricted cash		148,406
Accounting Standards Update 2016-18 | Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash provided by operating activities		222
Cash provided by financing activities		6,065
Net change in cash, cash equivalents, and restricted cash		$ 6,287

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 140,255	$ 109,479	$ 362,791	$ 274,282
Other revenue
Disaggregation of Revenue [Line Items]
Revenue	2,640	2,251	7,356	6,043
Real estate services
Disaggregation of Revenue [Line Items]
Revenue	126,265	103,864	332,047	262,894
Real estate services | Brokerage revenue
Disaggregation of Revenue [Line Items]
Revenue	118,809	97,787	312,306	247,327
Real estate services | Partner revenue
Disaggregation of Revenue [Line Items]
Revenue	7,456	6,077	19,741	15,567
Properties
Disaggregation of Revenue [Line Items]
Revenue	$ 11,350	$ 3,364	$ 23,388	$ 5,345

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Changes in Accrued Revenue and Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, December 31, 2017	$ 160
Charges	(28)
Write-offs	25
Balance, September 30, 2018	157
Accrued revenue		$ 13,411
Less: Allowance for doubtful accounts	$ 160	157
Accrued revenue, net		$ 13,254

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Money market funds | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 440,216	$ 177,235
Forward sales commitments | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	71	9
Derivative liability	(6)	(2)
Interest rate lock commitments | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	120	29
Derivative liability	$ (25)	$ (4)

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 42,671	$ 36,456
Accumulated depreciation and amortization	(19,310)	(14,138)
Property and equipment, net	23,361	22,318
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	17,610	16,039
Website and software development costs
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 18,153	14,501
Website and software development costs | Minimum
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	1 year
Website and software development costs | Maximum
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	3 years
Computer and office equipment
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	3 years
Property and equipment, gross	$ 2,678	2,192
Software
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	3 years
Property and equipment, gross	$ 594	685
Furniture
Property, Plant and Equipment [Line Items]
Useful Lives (Years)	7 years
Property and equipment, gross	$ 3,636	$ 3,039

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Depreciation and Amortization	$ 2,099	$ 1,665	$ 5,757	$ 4,960

Acquired Intangible Assets - Sc

Acquired Intangible Assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross	$ 4,880	$ 4,880
Accumulated Amortization	(1,952)	(1,586)
Net	$ 2,928	3,294
Trade names
Finite-Lived Intangible Assets [Line Items]
Useful Live (years)	10 years
Gross	$ 1,040	1,040
Accumulated Amortization	(416)	(338)
Net	$ 624	702
Developed technology
Finite-Lived Intangible Assets [Line Items]
Useful Live (years)	10 years
Gross	$ 2,980	2,980
Accumulated Amortization	(1,192)	(968)
Net	$ 1,788	2,012
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Useful Live (years)	10 years
Gross	$ 860	860
Accumulated Amortization	(344)	(280)
Net	$ 516	$ 580

Acquired Intangible Assets - Na

Acquired Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization	$ 122	$ 122	$ 366	$ 366
2,018	488		488
2,019	488		488
2,020	488		488
2,021	488		488
2,022	488		488
Total	$ 2,440		$ 2,440

Segment Reporting - Narrative (

Segment Reporting - Narrative (Details)	9 Months Ended
	Sep. 30, 2018segment
Segment Reporting [Abstract]
Number of operating segments	5
Number of reportable segments	2

Segment Reporting - Reconciliat

Segment Reporting - Reconciliation of Operating Profit (Loss) from Segments to Consolidated (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	$ 140,255	$ 109,479	$ 362,791	$ 274,282
Cost of revenue	97,950	70,166	269,576	191,633
Gross profit	42,305	39,313	93,215	82,649
Operating expenses	39,016	29,066	124,643	96,252
Interest income	1,775	311	3,082	387
Interest expense	1,610	0	1,610	0
Other income, net	21	0	200	13
Net income (loss)	3,475	10,558	(29,756)	(13,203)	$ (15,002)
Real estate services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	126,265	103,864	332,047	262,894
Properties
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	11,350	3,364	23,388	5,345
Operating Segments | Real estate services
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	126,265	103,864	332,047	262,894
Cost of revenue	83,274	64,258	236,775	178,850
Gross profit	42,991	39,606	95,272	84,044
Operating Segments | Properties
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	11,350	3,364	23,388	5,345
Cost of revenue	11,656	3,326	24,086	5,361
Gross profit	(306)	38	(698)	(16)
Other revenue
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	2,640	2,251	7,356	6,043
Cost of revenue	3,020	2,582	8,715	7,422
Gross profit	$ (380)	$ (331)	$ (1,359)	$ (1,379)

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock and Stockholders' Equity - Narrative (Details)	Sep. 30, 2018$ / sharesshares	Dec. 31, 2017$ / sharesshares	Aug. 02, 2017	Dec. 31, 2016shares
Temporary Equity And Stockholder's Equity [Abstract]
Conversion basis			1
Redeemable convertible preferred stock, authorized (in shares)	0
Redeemable convertible preferred stock, issued (in shares)	0
Redeemable convertible preferred stock outstanding (in shares)	0	0		55,422,002
Common stock, authorized (in shares)	500,000,000	500,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001
Preferred stock, outstanding (in shares)	0	0
Preferred stock, issued (in shares)	0	0

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Stock and Stockholders' Equity - Accretion of Redeemable Convertible Preferred Stock (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock	$ 0	$ (40,224)	$ 0	$ (175,915)
Series A-1
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock		(1,119)		(4,904)
Series A-2
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock		(28)		(123)
Series A-3
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock		(2,349)		(10,192)
Series B
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock		(9,284)		(40,336)
Series C
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock		(8,530)		(37,062)
Series D
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock		(7,300)		(31,717)
Series E
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock		(2,948)		(12,884)
Series F
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock		(4,541)		(20,184)
Series G
Temporary Equity [Line Items]
Accretion of redeemable convertible preferred stock		$ (4,125)		$ (18,513)

Redeemable Convertible Prefer_5

Redeemable Convertible Preferred Stock and Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2018	Dec. 31, 2017	Jul. 26, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options issued and outstanding (in shares)	10,150,522	13,180,950
Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options issued and outstanding (in shares)	10,150,522	13,180,950
Restricted stock units outstanding (in shares)	2,081,173	981,276
Shares available for future equity grants (in shares)	6,214,739	7,026,071
Total common stock reserved (in shares)	18,446,434	21,188,297	7,898,159
2017 Employee Stock Purchase Plan:
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued under employee stock purchase plan (in shares)	187,076	0
Shares available for future purchases under employee stock purchase plan (in shares)	2,227,612	1,600,000
Total common stock reserved (in shares)	2,414,688	1,600,000

Stock-based Compensation - Narr

Stock-based Compensation - Narrative (Details) - USD ($) $ in Thousands	Jul. 27, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Feb. 22, 2018	Dec. 31, 2017	Jul. 26, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation, options		$ 10,221		$ 10,221
Share-based compensation expense		$ 5,498	$ 2,709	$ 14,472	$ 8,028
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved (in shares)		2,414,688		2,414,688			1,600,000
Stock purchased under employee stock purchase plan (in shares)		0
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved (in shares)		18,446,434		18,446,434			21,188,297	7,898,159
Percentage of common stock, outstanding				5.00%
Restricted stock units outstanding (in shares)		2,081,173		2,081,173			981,276
Employee stock purchase plan shares | 2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved (in shares)	1,600,000
Percentage of common stock, outstanding	1.00%
Increase in common stock reserved (in shares)						814,688
Purchase price of common stock, percentage of market price of common stock				85.00%
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, period for recognition				3 years 3 months 11 days
Unrecognized stock-based compensation		$ 41,148		$ 41,148
Grants in period (in shares)				1,400,212
Restricted stock units outstanding (in shares)		2,081,173		2,081,173			981,276
Restricted stock units | 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life				10 years
Award vesting period				4 years
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense, period for recognition				1 year 8 months 16 days
Employee Stock Option | 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life				10 years
Award vesting period				4 years
Performance RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period (in shares)		8,913
Achievement percentage of performance conditions		100.00%
Restricted stock units outstanding (in shares)		143,890		143,890
Requisite service period		3 years
Share-based compensation expense		$ 379
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of units vesting		0.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of units vesting		200.00%

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Value Assumptions (Details) - $ / shares	Jul. 01, 2018	Sep. 30, 2018
2017 Employee Stock Purchase Plan | Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life	6 months
Volatility	39.25%
Risk-free interest rate	2.14%
Dividend yield	0.00%
Weighted-average grant date fair value (in dollars per share)	$ 5.94
2004 Equity Incentive Plan | Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life		7 years
Dividend yield		0.00%
Weighted-average grant date fair value (in dollars per share)		$ 4.86
Minimum | 2004 Equity Incentive Plan | Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility		37.88%
Risk-free interest rate		1.96%
Maximum | 2004 Equity Incentive Plan | Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility		40.97%
Risk-free interest rate		2.26%

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Number Of Options
Outstanding at December 31, 2017 (in shares)	13,180,950
Options granted (in shares)	0
Options exercised (in shares)	(2,653,008)
Options forfeited (in shares)	(367,541)
Options canceled (in shares)	(9,879)
Outstanding at September 30, 2018 (in shares)	10,150,522	13,180,950
Options exercisable at September 30, 2018 (in shares)	7,750,226
Weighted- Average Exercise Price
Outstanding at December 31, 2017 (in dollars per share)	$ 6.30
Options granted (in dollars per share)	0
Options exercised (in dollars per share)	5.17
Options forfeited (in dollars per share)	9.45
Options canceled (in dollars per share)	8.26
Outstanding at September 30, 2018 (in dollars per share)	6.48	$ 6.30
Options exercisable at September 30, 2018 (in dollars per share)	$ 5.67
Stock Option Activity, Additional Disclosures
Weighted average remaining contractual life outstanding	6 years 3 months 8 days	7 years 7 days
Weighted average remaining contractual life exercisable	5 years 9 months 15 days
Options outstanding, Aggregate intrinsic value	$ 124,054	$ 329,786
Options exercisable, Aggregate intrinsic value	$ 100,976

Stock-based Compensation - Sc_2

Stock-based Compensation - Schedule of Restricted Stock Unit Activity (Details) - Restricted stock units	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Restricted Stock Units
Unvested outstanding at December 31, 2017 (in shares) | shares	981,276
Granted (in shares) | shares	1,400,212
Vested (in shares) | shares	(127,746)
Forfeited or canceled (in shares) | shares	(172,569)
Unvested outstanding at September 30, 2018 (in shares) | shares	2,081,173
Weighted Average Grant-Date Fair Value
Unvested outstanding at December 31, 2017 (in dollars per share) | $ / shares	$ 22.78
Granted (in dollars per share) | $ / shares	21.17
Vested (in dollars per share) | $ / shares	22.57
Forfeited or canceled (in dollars per share) | $ / shares	21.86
Unvested outstanding at September 30, 2018 (in dollars per share) | $ / shares	$ 21.79

Stock-based Compensation - Allo

Stock-based Compensation - Allocation of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 5,498	$ 2,709	$ 14,472	$ 8,028
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	1,370	715	4,061	2,129
Technology and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	2,135	819	5,334	2,301
Marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	155	121	431	362
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 1,838	$ 1,054	$ 4,646	$ 3,236

Net Income (Loss) per Share A_3

Net Income (Loss) per Share Attributable to Common Stock - Narrative (Details)	Aug. 02, 2017class
Earnings Per Share [Abstract]
Number of classes of stock	1

Net Income (Loss) per Share A_4

Net Income (Loss) per Share Attributable to Common Stock - Computation of Net Income (loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Numerator:
Net income (loss)	$ 3,475	$ 10,558	$ (29,756)	$ (13,203)	$ (15,002)
Accretion of preferred stock	0	(40,224)	0	(175,915)
Net income (loss) attributable to common stock—basic	3,475	(29,666)	(29,756)	(189,118)
Net income (loss) attributable to common stock—diluted	$ 3,475	$ (29,666)	$ (29,756)	$ (189,118)
Weighted average shares:
Basic (in shares)	87,743,223	58,868,903	84,327,266	29,678,082
Dilutive shares from stock plans (in shares)	6,899,240	0	0	0
Diluted (in shares)	94,642,463	58,868,903	84,327,266	29,678,082
Net income (loss) per share:
Net income (loss) per share attributable to common stock—basic (in dollars per share)	$ 0.04	$ (0.50)	$ (0.35)	$ (6.37)
Net income (loss) per share attributable to common stock—diluted (in dollars per share)	$ 0.04	$ (0.50)	$ (0.35)	$ (6.37)

Net Income (Loss) per Share A_5

Net Income (Loss) per Share Attributable to Common Stock - Summary of Anti-dilutive Stock Equivalents (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (in shares)	238,668	68,720,341	12,231,695	68,720,341
Redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (in shares)	0	55,422,002	0	55,422,002
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (in shares)	0	13,298,339	10,150,522	13,298,339
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share (in shares)	238,668	0	2,081,173	0

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Net impact on tax expense due to The Tax Act					$ 0
Effective tax rate	0.00%	0.00%	0.00%	0.00%
Operating loss unavailable for carryforward						$ 1,538,000
Federal Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards					87,071,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards					$ 4,231,000

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Rent expense			$ 2,015,000	$ 1,705,000	$ 5,859,000	$ 6,030,000
Debt Instrument [Line Items]
Amount outstanding under Warehouse Agreement	$ 5,790,000	$ 2,016,000	5,790,000		5,790,000
Texas Capital Bank, Warehouse Agreement | Mortgage Warehouse Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 10,000,000
Discount on variable interest rate		0.50%
Stated interest rate		3.00%
Lender participation interest		97.00%
Amount outstanding under Warehouse Agreement	5,791,000	$ 833,000	5,791,000		5,791,000
Western Alliance Bank | Mortgage Warehouse Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 10,000,000		$ 10,000,000		$ 10,000,000
Stated interest rate	3.50%		3.50%		3.50%
Basis spread on variable interest rate	2.75%
Lender participation interest	98.00%
Amount outstanding under Warehouse Agreement	$ 0	$ 1,184,000	$ 0		$ 0
Minimum
Debt Instrument [Line Items]
Operating lease term					1 year
Maximum
Debt Instrument [Line Items]
Operating lease term					11 years

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Future Minimum Payments (Details) $ in Thousands	Sep. 30, 2018USD ($)
Facility Leases
2,018	$ 2,256
2,019	9,940
2,020	9,668
2,021	9,040
2022 and thereafter	34,922
Total minimum lease payments	65,826
Other Commitments
2,018	4,556
2,019	2,386
2,020	218
2,021	83
2022 and thereafter	0
Total minimum lease payments	$ 7,243

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued compensation and benefits	$ 29,370	$ 19,543
Legal fees and settlements	270	2,230
Miscellaneous accrued liabilities	7,892	4,832
Total accrued liabilities:	$ 37,532	$ 26,605

Other Payables (Details)

Other Payables (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Customer deposits	$ 11,773	$ 4,068
Miscellaneous payables	394	0
Total other payables:	$ 12,167	$ 4,068

Retirement Plan (Details)

Retirement Plan (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Retirement Benefits [Abstract]
Minimum percentage of compensation allowed to be deferred			1.00%
Maximum percentage of compensation allowed to be deferred			100.00%
Employer matching and profit-sharing contributions	$ 0	$ 0	$ 0	$ 0

Convertible Senior Notes (Detai

Convertible Senior Notes (Details) $ / shares in Units, $ in Thousands	Jul. 23, 2018USD ($)$ / shares	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior notes		$ 138,953	$ 0
Proceeds from issuance of convertible debt, net of underwriting discounts	$ 138,953
Debt issuance costs, gross	4,797
Debt issuance costs, gross, carrying amount of liability component	3,832
Debt issuance costs, gross, carrying amount of equity component	965
1.75% Convertible Senior Notes due 2023
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior notes	143,750
Proceeds from issuance of convertible debt, net of underwriting discounts	$ 138,953
Stated interest rate	1.75%
Debt instrument, redemption price, percentage	100.00%
Debt instrument, convertible, conversion ratio	0.0327332
Debt instrument, convertible, conversion price (in dollars per share) | $ / shares	$ 30.55
Premium percentage of conversion price	30.00%
Debt issuance costs, gross, carrying amount of equity component		965
Public Offerings
Debt Instrument [Line Items]
Offering price (in dollars per share) | $ / shares	$ 23.50
Fair Value, Inputs, Level 2 | 1.75% Convertible Senior Notes due 2023
Debt Instrument [Line Items]
Debt instrument, fair value		$ 129,195

Convertible Senior Notes - Comp

Convertible Senior Notes - Components of The Notes (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jul. 23, 2018
Debt Instrument [Line Items]
Less: debt issuance costs		$ (965)
1.75% Convertible Senior Notes due 2023
Debt Instrument [Line Items]
Principal	$ 143,750
Less: debt discount, net of amortization	(27,919)
Less: debt issuance costs, net of amortization	(3,701)
Net carrying amount of the Notes	112,130
Allocated value of the conversion feature	28,916
Less: debt issuance costs	(965)
Allocated value of the conversion feature	$ 27,951

Convertible Senior Notes - Inte

Convertible Senior Notes - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Debt Instrument [Line Items]
Total amortization of debt issuance costs and accretion of equity portion			$ 1,128	$ 0
Total interest expense related to the Notes	$ 1,610	$ 0	$ 1,610	$ 0
1.75% Convertible Senior Notes due 2023
Debt Instrument [Line Items]
Amortization of debt discount	997
Amortization of debt issuance costs	131
Total amortization of debt issuance costs and accretion of equity portion	1,128
Contractual interest expense	482
Total interest expense related to the Notes	$ 1,610
Effective interest rate of the liability component	7.10%		7.10%