Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies 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”). All amounts are presented in thousands, except share and per share data. The financial information as of December 31, 2018 is derived from the audited consolidated financial statements and notes for the year ended December 31, 2018 included in Item 8 in the Annual Report on Form 10-K (the “2018 Annual Report”) of Redfin Corporation (the "Company" or "Redfin"). The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the notes and management’s discussion and analysis of the consolidated financial statements included in the 2018 Annual Report. 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 March 31, 2019, the statements of comprehensive loss, cash flows, and stockholders' equity for the three months ended March 31, 2019 and 2018. The results for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 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. 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 evaluates its estimates on an ongoing basis. During the three months ended March 31, 2019, the estimated useful life of capitalized software for internal use was updated from one to two years. This change in estimate was not material. In addition, with the adoption of Accounting Standards Codification Topic 842, Leases ("ASC 842" or "Topic 842"), the Company estimated its incremental borrowing rate for the determination of the present value of lease payments. Further description of the impact of this pronouncement is included in Note 6: Leases. The amounts ultimately realized from the affected assets or 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 Accounting Pronouncements—In January 2019, the Company adopted ASU 2016-02, Leases (Topic 842), using the optional alternative transition method under ASU 2018-11, Leases (Topic 842) Targeted Improvements. The optional alternative transition method 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. The Company evaluated its portfolio of leases and determined a cumulative-effect adjustment to the opening balance of retained earnings was not needed, as the portfolio of leases contains only operating leases. The Company elected the package of practical expedients permitted under the transition guidance within the standard, allowing the Company to carry forward the historical lease classification, carry forward the conclusions on whether current or expired contracts contain leases, and carry forward the accounting for initial direct costs for existing leases. Additionally, the Company elected the practical expedient for use of hindsight to determine the lease term for existing leases whereby it evaluated the performance of existing leases in relation to our leasing strategy and determined that most renewal options would not be reasonably certain to be exercised. This resulted in the shortening of lease terms for the existing leases. Adoption of the standard resulted in the recording of right of use assets and corresponding lease liabilities of $33,953 and $49,395, respectively, as of January 1, 2019, the difference of which is due to lease incentives. Further description of the impact of this pronouncement is included in Note 6: Leases. In January 2019, the Company adopted the guidance in the U.S. Securities and Exchange Commission (the "SEC") final rule under SEC Release No. 33-10532, Disclosure Update and Simplification. In August 2018, the SEC issued the final rule 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. Recently Issued Accounting Pronouncements—In August 2018, the Financial Accounting Standards Board ("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 noncancelable 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 for public entities for fiscal years beginning after December 15, 2019. The Company has not yet completed its assessment of the impact of the new standard on the Company’s consolidated financial statements.

Summary of Significant Accounting Policies

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”). All amounts are presented in thousands, except share and per share data.

The financial information as of December 31, 2018 is derived from the audited consolidated financial statements and notes for the year ended December 31, 2018 included in Item 8 in the Annual Report on Form 10-K (the “2018 Annual Report”) of Redfin Corporation (the "Company" or "Redfin"). The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the notes and management’s discussion and analysis of the consolidated financial statements included in the 2018 Annual Report.

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 March 31, 2019, the statements of comprehensive loss, cash flows, and stockholders' equity for the three months ended March 31, 2019 and 2018. The results for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 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.

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 evaluates its estimates on an ongoing basis. During the three months ended March 31, 2019, the estimated useful life of capitalized software for internal use was updated from one to two years. This change in estimate was not material. In addition, with the adoption of Accounting Standards Codification Topic 842, Leases ("ASC 842" or "Topic 842"), the Company estimated its incremental borrowing rate for the determination of the present value of lease payments. Further description of the impact of this pronouncement is included in Note 6: Leases. The amounts ultimately realized from the affected assets or 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 Accounting Pronouncements—In January 2019, the Company adopted ASU 2016-02, Leases (Topic 842), using the optional alternative transition method under ASU 2018-11, Leases (Topic 842) Targeted Improvements. The optional alternative transition method 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. The Company evaluated its portfolio of leases and determined a cumulative-effect adjustment to the opening balance of retained earnings was not needed, as the portfolio of leases contains only operating leases.

The Company elected the package of practical expedients permitted under the transition guidance within the standard, allowing the Company to carry forward the historical lease classification, carry forward the conclusions on whether current or expired contracts contain leases, and carry forward the accounting for initial direct costs for existing leases. Additionally, the Company elected the practical expedient for use of hindsight to determine the lease term for existing leases whereby it evaluated the performance of existing leases in relation to our leasing strategy and determined that most renewal options would not be reasonably certain to be exercised. This resulted in the shortening of lease terms for the existing leases.

Adoption of the standard resulted in the recording of right of use assets and corresponding lease liabilities of $33,953 and $49,395, respectively, as of January 1, 2019, the difference of which is due to lease incentives. Further description of the impact of this pronouncement is included in Note 6: Leases.

In January 2019, the Company adopted the guidance in the U.S. Securities and Exchange Commission (the "SEC") final rule under SEC Release No. 33-10532, Disclosure Update and Simplification. In August 2018, the SEC issued the final rule 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.

Recently Issued Accounting Pronouncements—In August 2018, the Financial Accounting Standards Board ("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 noncancelable 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 for public entities for fiscal years beginning after December 15, 2019. The Company has not yet completed its assessment of the impact of the new standard on the Company’s consolidated financial statements.