Organization	6 Months Ended
Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization We were organized in Delaware on January 7, 2008, and commenced operations on May 20, 2008 following the completion of our initial public offering ("IPO"). Our common stock is traded on The NASDAQ Global Select Market under the symbol "AGNC." We operate so as to qualify to be taxed as a real estate investment trust ("REIT") under the Internal Revenue Code of 1986, as amended (the "Internal Revenue Code"). As a REIT, we are required to distribute annually 90% of our taxable net income. As long as we continue to qualify as a REIT, we will generally not be subject to U.S. federal or state corporate taxes on our taxable net income to the extent that we distribute our annual taxable net income to our stockholders on a timely basis. It is our intention to distribute 100% of our taxable net income, after application of available tax attributes, within the limits prescribed by the Internal Revenue Code, which may extend into the subsequent tax year. We earn income primarily from investing in residential mortgage-backed securities for which the principal and interest payments are guaranteed by a U.S. Government-sponsored enterprise or a U.S. Government agency ("Agency RMBS") on a leveraged basis. We may also invest in other types of mortgage and mortgage-related securities, such as credit risk transfer ("CRT") securities and non-Agency residential and commercial mortgage-backed securities ("non-Agency RMBS" and "CMBS," respectively), where repayment of principal and interest is not guaranteed by a U.S. Government-sponsored enterprise or U.S. Government agency (see Note 3 for further details). Our principal objective is to provide our stockholders with attractive risk-adjusted returns through a combination of monthly dividends and net asset value (also referred to as "net book value" or "NAV") accretion. We generate income from the interest earned on our investment assets, net of associated borrowing and hedging activities, and net realized gains and losses on our investments and hedging activities. We fund our investments primarily through borrowings structured as repurchase agreements. Prior to July 1, 2016, we were externally managed by AGNC Management, LLC (our "Manager"). On July 1, 2016, we completed the acquisition of all of the outstanding membership interests of AGNC Mortgage Management, LLC ("AMM"), the parent company of our Manager, from American Capital Asset Management, LLC ("ACAM"), a wholly owned portfolio company of American Capital, Ltd. ("ACAS"). AMM is also the parent company of MTGE Management, LLC, the external manager of MTGE Investment Corp. ("MTGE") (NASDAQ: MTGE). Following the closing of the acquisition of AMM, we became internally managed and are no longer affiliated with ACAS.

Organization

We were organized in Delaware on January 7, 2008, and commenced operations on May 20, 2008 following the completion of our initial public offering ("IPO"). Our common stock is traded on The NASDAQ Global Select Market under the symbol "AGNC."

We operate so as to qualify to be taxed as a real estate investment trust ("REIT") under the Internal Revenue Code of 1986, as amended (the "Internal Revenue Code"). As a REIT, we are required to distribute annually 90% of our taxable net income. As long as we continue to qualify as a REIT, we will generally not be subject to U.S. federal or state corporate taxes on our taxable net income to the extent that we distribute our annual taxable net income to our stockholders on a timely basis. It is our intention to distribute 100% of our taxable net income, after application of available tax attributes, within the limits prescribed by the Internal Revenue Code, which may extend into the subsequent tax year.

We earn income primarily from investing in residential mortgage-backed securities for which the principal and interest payments are guaranteed by a U.S. Government-sponsored enterprise or a U.S. Government agency ("Agency RMBS") on a leveraged basis. We may also invest in other types of mortgage and mortgage-related securities, such as credit risk transfer ("CRT") securities and non-Agency residential and commercial mortgage-backed securities ("non-Agency RMBS" and "CMBS," respectively), where repayment of principal and interest is not guaranteed by a U.S. Government-sponsored enterprise or U.S. Government agency (see Note 3 for further details).

Our principal objective is to provide our stockholders with attractive risk-adjusted returns through a combination of monthly dividends and net asset value (also referred to as "net book value" or "NAV") accretion. We generate income from the interest earned on our investment assets, net of associated borrowing and hedging activities, and net realized gains and losses on our investments and hedging activities. We fund our investments primarily through borrowings structured as repurchase agreements.

Prior to July 1, 2016, we were externally managed by AGNC Management, LLC (our "Manager"). On July 1, 2016, we completed the acquisition of all of the outstanding membership interests of AGNC Mortgage Management, LLC ("AMM"), the parent company of our Manager, from American Capital Asset Management, LLC ("ACAM"), a wholly owned portfolio company of American Capital, Ltd. ("ACAS"). AMM is also the parent company of MTGE Management, LLC, the external manager of MTGE Investment Corp. ("MTGE") (NASDAQ: MTGE). Following the closing of the acquisition of AMM, we became internally managed and are no longer affiliated with ACAS.