Organization and Investment Objective	3 Months Ended
Organization and Investment Objective	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Investment Objective	Organization and Investment Objective Ellington Residential Mortgage REIT, or "EARN," was formed as a Maryland real estate investment trust, or "REIT," on August 2, 2012, and commenced operations on September 25, 2012. EARN conducts its business through its wholly owned subsidiaries, EARN OP GP LLC, or the "General Partner," and Ellington Residential Mortgage LP, or the "Operating Partnership," which were formed as a Delaware limited liability company and a Delaware limited partnership, respectively, on July 31, 2012 and commenced operations on September 25, 2012. The Operating Partnership conducts its business of acquiring, investing in, and managing residential mortgage- and real estate-related assets through its wholly owned subsidiaries. EARN, the General Partner, the Operating Partnership, and their consolidated subsidiaries are hereafter defined as the "Company." Ellington Residential Mortgage Management LLC, or the "Manager," serves as the Manager of the Company pursuant to the terms of the Fifth Amended and Restated Management Agreement, or the "Management Agreement." The Manager is an affiliate of Ellington Management Group, L.L.C., or "EMG," an investment management firm that is an SEC-registered investment adviser with a 25-year history of investing in a broad spectrum of mortgage-backed securities and related derivatives, with an emphasis on the residential mortgage-backed securities, or "RMBS," market. In accordance with the terms of the Management Agreement and the Services Agreement (as described in Note 9), the Manager is responsible for administering the Company's business activities and day-to-day operations, and performs certain services, subject to oversight by the Board of Trustees. See Note 9 for further information on the Management Agreement. The Company acquires and manages RMBS, for which the principal and interest payments are guaranteed by a U.S. government agency or a U.S. government-sponsored entity, or "Agency RMBS," and RMBS that do not carry such guarantees, or "non-Agency RMBS," such as RMBS backed by prime jumbo, Alternative A-paper, manufactured housing, and subprime residential mortgage loans. Agency RMBS include both Agency pools and Agency collateralized mortgage obligations, or "CMOs," and non-Agency RMBS primarily consist of non-Agency CMOs, both investment grade and non-investment grade. The Company may also acquire and manage CMBS, mortgage servicing rights, credit risk transfer securities, residential mortgage loans, and other mortgage- and real estate-related assets. The Company may also invest in other instruments including, but not limited to, forward-settling To-Be-Announced Agency pass-through certificates, or "TBAs," interest rate swaps and swaptions, U.S. Treasury securities, Eurodollar and U.S. Treasury futures, other financial derivatives, and cash equivalents. The Company's targeted investments may range from unrated first loss securities to AAA senior securities. The Company has elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended, or "the Code," and conducts its operations to qualify and be taxed as a REIT. As a REIT, the Company is required to distribute annually at least 90% of its taxable income. As long as the Company continues to qualify as a REIT, it will not be subject to U.S. federal corporate taxes on its taxable income to the extent that it distributes all of its annual taxable income to its shareholders within the time limits prescribed by the Code. It is the intention of the Company to distribute at least 100% of its taxable income, after application of available tax attributes, within the time limits prescribed by the Code, which may extend into the subsequent taxable year. COVID-19 Impact During the first quarter of 2020, there was a worldwide outbreak of a novel coronavirus disease, or "COVID-19." The outbreak was declared a pandemic by the World Health Organization and numerous countries, including the United States, have responded by instituting quarantines or lockdowns, imposing restrictions on travel, restrictions on the ability of individuals to assemble in groups, and restrictions on the ability of certain businesses to operate, all of which have resulted in significant disruptions in the U.S. and global economies. In mid-March 2020, adverse economic conditions related to the COVID-19 pandemic began to impact the Company's financial position and results of operations. The COVID-19 pandemic has contributed to volatility, dislocations in the financial markets, and illiquidity. As a result, the Company received margin calls under its repurchase agreements that were higher than typical historical levels. The Company satisfied all of these margin calls. Actions during the second half of March 2020 by the U.S. Federal Reserve helped stabilize the market for Agency RMBS. In light of the heightened levels of market volatility and systemic liquidity risk experienced during the first quarter of 2020, the Company proactively reduced the size of its Agency RMBS portfolio, thereby bolstering its liquidity and lowering its leverage. The Company's management team has implemented business continuity plans, and the Company, the Manager, and EMG continue to be fully operational in a largely work-from-home environment.