Organization	12 Months Ended
Dec. 31, 2012
Organization [Abstract]
Organization	Organization American Capital Agency Corp. ("AGNC", the "Company", "we", "us", and "our") was 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”). Therefore, substantially all of our assets, other than our taxable REIT subsidiary ("TRS"), consist of qualified real estate assets (as defined under 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 all of our annual taxable net income to our stockholders. It is our intention to distribute 100% of our taxable income, after application of available tax attributes, within the limits prescribed by the Internal Revenue Code, which may extend into the subsequent taxable year. We are externally managed by American Capital AGNC Management, LLC (our “Manager”), an affiliate of American Capital, Ltd. (“American Capital”). We earn income primarily from investing on a leveraged basis in agency mortgage-backed securities ("agency MBS"). These investments consist of residential mortgage pass-through securities and collateralized mortgage obligations (“CMOs”) for which the principal and interest payments are guaranteed by government-sponsored entities, such as the Federal National Mortgage Association (“Fannie Mae”) and the Federal Home Loan Mortgage Corporation (“Freddie Mac”), or by a U.S. Government agency, such as the Government National Mortgage Association (“Ginnie Mae”) (collectively referred to as “GSEs”). We may also invest in agency debenture securities issued by Freddie Mac, Fannie Mae or the Federal Home Loan Bank ("FHLB"). We refer to agency MBS and agency debenture securities collectively as "investment securities" and we refer to the specific investment securities in which we invest as our "investment portfolio". Our principal objective is to preserve our net asset value (also referred to as "net book value", "NAV" and "stockholders' equity") while generating attractive risk-adjusted returns for distribution to our stockholders through regular quarterly dividends from the combination of our net interest income and net realized gains and losses on our investments and hedging activities. We fund our investments primarily through short-term borrowings structured as repurchase agreements.

Organization

12 Months Ended

Dec. 31, 2012

American Capital Agency Corp. ("AGNC", the "Company", "we", "us", and "our") was 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”). Therefore, substantially all of our assets, other than our taxable REIT subsidiary ("TRS"), consist of qualified real estate assets (as defined under 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 all of our annual taxable net income to our stockholders. It is our intention to distribute 100% of our taxable income, after application of available tax attributes, within the limits prescribed by the Internal Revenue Code, which may extend into the subsequent taxable year.

We are externally managed by American Capital AGNC Management, LLC (our “Manager”), an affiliate of American Capital, Ltd. (“American Capital”).

We earn income primarily from investing on a leveraged basis in agency mortgage-backed securities ("agency MBS"). These investments consist of residential mortgage pass-through securities and collateralized mortgage obligations (“CMOs”) for which the principal and interest payments are guaranteed by government-sponsored entities, such as the Federal National Mortgage Association (“Fannie Mae”) and the Federal Home Loan Mortgage Corporation (“Freddie Mac”), or by a U.S. Government agency, such as the Government National Mortgage Association (“Ginnie Mae”) (collectively referred to as “GSEs”). We may also invest in agency debenture securities issued by Freddie Mac, Fannie Mae or the Federal Home Loan Bank ("FHLB"). We refer to agency MBS and agency debenture securities collectively as "investment securities" and we refer to the specific investment securities in which we invest as our "investment portfolio".

Our principal objective is to preserve our net asset value (also referred to as "net book value", "NAV" and "stockholders' equity") while generating attractive risk-adjusted returns for distribution to our stockholders through regular quarterly dividends from the combination of our net interest income and net realized gains and losses on our investments and hedging activities. We fund our investments primarily through short-term borrowings structured as repurchase agreements.