Organization, Description of Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Description of Business and Basis of Presentation	Organization, Description of Business and Basis of Presentation United Rentals, Inc. (“Holdings,” “URI” or the “Company”) is principally a holding company and conducts its operations primarily through its wholly owned subsidiary, United Rentals (North America), Inc. (“URNA”), and subsidiaries of URNA. Holdings’ primary asset is its sole ownership of all issued and outstanding shares of common stock of URNA. URNA’s various credit agreements and debt instruments place restrictions on its ability to transfer funds to its shareholder. We rent equipment to a diverse customer base that includes construction and industrial companies, manufacturers, utilities, municipalities, homeowners and government entities in the United States, Canada and Europe. In July 2018, we completed the acquisition of BakerCorp International Holdings, Inc. (“BakerCorp”), which allowed for our entry into select European markets. In addition to renting equipment, we sell new and used rental equipment, as well as related contractor supplies, parts and service. We have prepared the accompanying unaudited condensed consolidated financial statements in accordance with the accounting policies described in our annual report on Form 10-K for the year ended December 31, 2019 (the “2019 Form 10-K”) and the interim reporting requirements of Form 10-Q. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) have been condensed or omitted. These unaudited condensed consolidated financial statements should be read in conjunction with the 2019 Form 10-K. In our opinion, all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair presentation of financial condition, operating results and cash flows for the interim periods presented have been made. Interim results of operations are not necessarily indicative of the results of the full year. COVID-19 The novel coronavirus (“COVID-19”) was first identified in people in late 2019. COVID-19 spread rapidly throughout the world and, in March 2020, the World Health Organization characterized COVID-19 as a pandemic. COVID-19 is a pandemic of respiratory disease spreading from person-to-person that poses a serious public health risk. It has significantly disrupted supply chains and businesses around the world. The extent and duration of the COVID-19 impact, on the operations and financial position of United Rentals and on the global economy, is uncertain. While visibility into future economic conditions remains limited, based on increased insight into near-term indicators, we reintroduced full-year 2020 guidance in July 2020, after having withdrawn it in April 2020. In October 2020, after reporting third quarter results, we raised our full-year 2020 guidance. The health and safety of our employees and customers remains our top priority, and we have also engaged in extensive contingency planning to manage the business impact of the pandemic. Prior to mid-March 2020, our results were largely in line with expectations. We began to experience a decline in revenues in March 2020, when rental volume declined in response to shelter-in-place orders and other market restrictions. COVID-19 is discussed in more detail throughout “Management’s Discussion and Analysis of Financial Condition and Results of Operations.” New Accounting Pronouncements Simplifying the Test for Goodwill Impairment. In January 2017, the Financial Accounting Standards Board ("FASB") issued guidance intended to simplify the subsequent accounting for goodwill acquired in a business combination. Prior guidance required utilizing a two-step process to review goodwill for impairment. A second step was required if there was an indication that an impairment may exist, and the second step required calculating the potential impairment by comparing the implied fair value of the reporting unit's goodwill (as if purchase accounting were performed on the testing date) with the carrying amount of the goodwill. The new guidance eliminates the second step from the goodwill impairment test. Under the new guidance, an entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount, and then recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value (although the loss should not exceed the total amount of goodwill allocated to the reporting unit). The guidance requires prospective adoption and will be effective for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019. We will adopt this guidance for the goodwill impairment test that we will conduct as of October 1, 2020, and do not expect the adoption of the guidance to have a significant impact on our financial statements. Simplifying the Accounting for Income Taxes. In December 2019, the FASB issued guidance intended to simplify the accounting for income taxes. The guidance removes the following exceptions: 1) exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income or a gain from other items, 2) exception to the requirement to recognize a deferred tax liability for equity method investments when a foreign subsidiary becomes an equity method investment, 3) exception to the ability not to recognize a deferred tax liability for a foreign subsidiary when a foreign equity method investment becomes a subsidiary and 4) exception to the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss for the year. Additionally, the guidance simplifies the accounting for income taxes by: 1) requiring that an entity recognize a franchise tax (or similar tax) that is partially based on income as an income-based tax and account for any incremental amount incurred as a non-income-based tax, 2) requiring that an entity evaluate when a step up in the tax basis of goodwill should be considered part of the business combination in which the book goodwill was originally recognized and when it should be considered a separate transaction, 3) specifying that an entity is not required to allocate the consolidated amount of current and deferred tax expense to a legal entity that is not subject to tax in its separate financial statements (although the entity may elect to do so (on an entity-by-entity basis) for a legal entity that is both not subject to tax and disregarded by the taxing authority), 4) requiring that an entity reflect the effect of an enacted change in tax laws or rates in the annual effective tax rate computation in the interim period that includes the enactment date and 5) making minor improvements for income tax accounting related to employee stock ownership plans and investments in qualified affordable housing projects accounted for using the equity method. The guidance will be effective for fiscal years and interim periods beginning after December 15, 2020. Different components of the guidance require retrospective, modified retrospective or prospective adoption, and early adoption is permitted. We will adopt this guidance when it becomes effective, in the first quarter of 2021, and the impact on our financial statements is not expected to be material. Guidance Adopted in 2020 Measurement of Credit Losses on Financial Instruments. In June 2016, the FASB issued guidance that requires companies to present certain financial assets net of the amount expected to be collected. Trade receivables (as noted below, excluding receivables arising from operating lease revenues) are the only material financial asset we have that is impacted by this guidance. The guidance requires the measurement of expected credit losses to be based on relevant information from past events, including historical experiences, current conditions and reasonable and supportable forecasts that affect collectibility. This guidance does not apply to receivables arising from operating lease revenues. As discussed in note 2 to the condensed consolidated financial statements, most of our equipment rental revenue is accounted for as lease revenue (such revenue represented 78 percent of our total revenues for the nine months ended September 30, 2020). We adopted this guidance in the first quarter of 2020, and the impact of adoption on our financial statements was not material. See note 2 (see "Receivables and contract assets and liabilities") for further discussion of our receivables. Facilitation of the Effects of Reference Rate Reform on Financial Reporting. In March 2020, the FASB issued guidance that provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by the discontinuation of the London Interbank Offered Rate (“LIBOR”) or by another reference rate expected to be discontinued. We adopted this guidance in 2020, and the impact of adoption on our financial statements was not material. The expedients and exceptions in this guidance are optional, and we are evaluating the potential future financial statement impact of any such expedient or exception that we may elect to apply.