Basis of Presentation and Nature of Operations	6 Months Ended
Basis of Presentation and Nature of Operations	Jun. 27, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Nature of Operations	Basis of Presentation and Nature of Operations Description of Business IAA, Inc., together with its subsidiaries (collectively referred to herein as “IAA” and "the Company") is a leading global digital marketplace connecting vehicle buyers and sellers. Leveraging leading-edge technology and focusing on innovation, IAA's unique platform facilitates the marketing and sale of total loss, damaged and low-value vehicles for a full spectrum of sellers. Headquartered in Westchester, Illinois, the Company has more than 200 facilities throughout the United States, Canada and the United Kingdom. The Company serves a global buyer base and a full spectrum of sellers, including insurance companies, dealerships, fleet lease and rental car companies, and charitable organizations. The Company offers sellers a comprehensive suite of services aimed at maximizing vehicle value, reducing administrative costs, shortening selling cycle time and delivering the highest economic returns. The Company's solutions provide global buyers with the vehicles they need to, among other things, fulfill their vehicle rebuild requirements, replacement part inventory or scrap demand. IAA provides global buyers multiple bidding/buying digital channels, innovative vehicle merchandising, efficient evaluation services and online bidding tools, enhancing the overall purchasing experience. The Company operates in two reportable segments: United States and International. The Company earns fees for its services from both buyers and sellers of vehicles sold through its channels. Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America ("U.S. GAAP") for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by U.S. GAAP for annual financial statements. In the opinion of management, the unaudited consolidated financial statements reflect all adjustments, generally consisting of normal recurring accruals, necessary for a fair statement of our financial results for the periods presented. Financial results for interim periods are not necessarily indicative of results that may be expected for the year as a whole. These unaudited consolidated financial statements and condensed notes thereto are unaudited and should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 27, 2020 included in the Company's Annual Report on Form 10-K filed with the Securities and Exchange Commission (the "SEC") on February 22, 2021. The Company's fiscal year consists of 52 weeks with every fifth year consisting of 53 weeks and ending either the last Sunday in December or the first Sunday in January. Fiscal 2021 contains 53 weeks and fiscal 2020 contained 52 weeks. Use of Estimates The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. GAAP. The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates based in part on assumptions about current, and for some estimates, future economic and market conditions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the period. Although the current estimates contemplate current conditions and expected future changes, as appropriate, it is reasonably possible that future conditions could differ from these estimates, which could materially affect the Company's results of operations and financial position. Among other effects, such changes could result in future impairments of goodwill, intangible assets and long-lived assets, additional allowances on accounts receivable and deferred tax assets and changes in litigation and other loss contingencies. Reclassification "Revenues" reported in the consolidated statements of income and segment information footnote in the prior period financial statements for the three and six months ended June 28, 2020 has been reclassified between "Service revenues" and "Vehicle sales" to conform to the current year's presentation. "Cost of services" reported in the consolidated statements of income and segment information footnote in the prior period financial statements for the three and six months ended June 28, 2020 has been reclassified between "Cost of services" and "Cost of vehicle sales" to conform to the current year's presentation. Recent Accounting Pronouncements Recently Issued and Adopted Accounting Pronouncements In December 2019, the Financial Accounting Standards Board issued Accounting Standards Update ("ASU") 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which simplifies the accounting for income taxes in various areas. The adoption of ASU 2019-12 on December 28, 2020 did not have any impact on the Company's consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted The Company does not believe that any recently issued, but not yet effective, accounting pronouncements, if adopted, would have a material impact on its unaudited consolidated financial statements or disclosures.