Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of presentation	Basis of Presentation The Company’s unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and applicable rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) for quarterly reports on Form 10-Q and Article 10-1 of Regulation S-X. Accordingly, some information and footnote disclosures required by GAAP for complete financial statements have been condensed or omitted pursuant to such rules and regulations. In the opinion of the Company’s management, the accompanying unaudited condensed consolidated financial statements and notes have been prepared on the same basis as the audited consolidated financial statements for the year ended December 31, 2018, except for the accounting policy changes detailed in Note 3 as a result of the Company’s adoption of the new leasing standard, and include all adjustments (consisting of normal recurring adjustments) necessary for a fair statement of the interim periods presented. The condensed consolidated balance sheet at December 31, 2018 has been derived from the audited financial statements at that date, but does not include all of the disclosures required by GAAP. The accompanying condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Form 10-K filed with the SEC on March 1, 2019.
Consolidation	Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of TrueCar and its wholly owned subsidiaries. Business acquisitions are included in the Company’s condensed consolidated financial statements from the date of the acquisition. The Company’s purchase accounting resulted in all assets and liabilities of acquired businesses being recorded at their estimated fair values on the acquisition dates. Equity investments through which the Company is able to exercise significant influence over but does not control the investee and is not the primary beneficiary of the investee’s activities are accounted for using the equity method. The Company’s share of the income or loss from equity method investments is recognized on a one-quarter lag due to the timing and availability of financial information. All intercompany balances and transactions have been eliminated in consolidation.
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 the disclosure of contingent assets and liabilities at the dates of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Assets and liabilities that are subject to judgment and use of estimates include sales allowances and allowances for doubtful accounts, contract assets, the fair value of a warrant asset and the related liability, the fair value of assets and liabilities assumed in business combinations, right-of-use assets and lease liabilities, the fair value of capitalized lease facilities, the recoverability of goodwill and long-lived assets, valuation allowances with respect to deferred tax assets, useful lives associated with property and equipment and intangible assets, lease exit liabilities, contingencies, and the valuation and assumptions underlying stock-based compensation and other equity instruments. On an ongoing basis, the Company evaluates its estimates compared to historical experience and trends, which form the basis for making judgments about the carrying value of assets and liabilities. In addition, the Company engaged valuation specialists to assist with management’s determination of the valuation of the fair value of a warrant asset and the related liability, right-of-use assets and lease liabilities, the fair value of capitalized lease facilities, the fair values of assets and liabilities assumed in business combinations, the fair value of reporting units in connection with annual goodwill impairment testing, the fair value of performance shares, and in periods prior to the Company’s initial public offering, valuation of common stock.
Segments	Segments The Company has one operating segment. During the first quarter of 2019, the Company’s chief operating decision maker (“CODM”) was the President and Chief Executive Officer and the Interim Chief Financial Officer and Chief Accounting Officer, who managed the Company’s operations based on consolidated financial information for purposes of evaluating financial performance and allocating resources. Effective April 1, 2019, the Company’s Interim Chief Financial Officer and Chief Accounting Officer resigned from his positions. From April 1, 2019, through May 31, 2019, the Company’s CODM was solely comprised of the President and Chief Executive Officer until his resignation on May 31, 2019. From June 1, 2019 through June 16, 2019, the CODM was comprised of the Interim President and Chief Executive Officer. Upon the hiring of the Chief Financial Officer on June 17, 2019 and through September 30, 2019, the CODM was comprised of both the Interim President and Chief Executive Officer and the Chief Financial Officer. During the three and nine months ended September 30, 2019, the Company’s operations were managed based on consolidated financial information for purposes of evaluating financial performance and allocating resources by the various CODM in place. The CODM reviews financial information on a consolidated basis, accompanied by information about dealer revenue, OEM incentive revenue, and forecasts, consulting and other revenue (Note 12). All of the Company’s principal operations, decision-making functions and assets are located in the United States.
Equity Method Investments	The Company recognizes its proportional share of the income or loss from the equity method investment on a one-quarter lag due to the timing and availability of financial information from Accu-Trade. Included in the initial carrying value of $22.9 million, which represents the fair value on the transaction date, was a basis difference of $21.0 million related to the difference between the cost of the investment and the Company’s proportionate share of the net assets of Accu-Trade. The carrying value of the equity method investment is primarily adjusted for the Company’s share in the losses of Accu-Trade and amortization of the basis difference. The Company amortizes its basis difference between the estimated fair value and the underlying book value of Accu-Trade’s technology and guarantor relationship over their respective useful lives using the straight-line method.
Recent accounting pronouncements	Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued new guidance that replaces the existing model for measuring the allowance for credit losses for financial assets measured at amortized cost (including trade accounts receivable) to a model that is based on the expected losses rather than incurred losses. Under the new credit loss model, lifetime expected credit losses on such financial assets are measured and recognized at each reporting date based on historical, current, and forecast information. This standard is effective for annual reporting periods beginning after December 15, 2019, including interim reporting periods within those annual reporting periods, with early adoption permitted. The Company continues to evaluate the impact of this guidance but the adoption is not expected to have a material impact on the Company’s consolidated financial statements. In August 2018, the FASB issued new guidance that aligns the requirements for capitalizing implementation costs incurred in a cloud computing arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). This standard is effective for annual reporting periods beginning after December 15, 2019, including interim reporting periods within those annual reporting periods, with early adoption permitted. The Company continues to evaluate the impact of this guidance but the adoption is not expected to have a material impact on the Company’s consolidated financial statements. In February 2016, the FASB issued guidance amending the existing accounting standards for lease accounting, including requiring lessees to recognize most leases on their balance sheets and making targeted changes to lessor accounting. On January 1, 2019, the Company adopted the new leasing standard using the prospective transition method. See Note 3 for further details. In June 2018, the FASB issued new guidance to simplify the accounting for nonemployee share-based payment transactions by expanding the scope of Accounting Standards Codification Topic 718, Compensation - Stock Compensation, to include share-based payment transactions for acquiring goods and services from nonemployees. Under the new standard, most of the guidance on stock compensation payments to nonemployees would be aligned with the requirements for share-based payments granted to employees. This standard is effective for annual reporting periods beginning after December 15, 2018, including interim reporting periods within those annual reporting periods, with early adoption permitted. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements.