Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies We are a stockholder-owned corporation organized and existing under the Federal National Mortgage Association Charter Act (the “Charter Act” or our “charter”). We are a government-sponsored enterprise and we are subject to government oversight and regulation. Our regulators include the Federal Housing Finance Agency (“FHFA”), the U.S. Department of Housing and Urban Development (“HUD”), the U.S. Securities and Exchange Commission (“SEC”), and the U.S. Department of the Treasury (“Treasury”). The U.S. government does not guarantee our securities or other obligations. We have been under conservatorship, with FHFA acting as conservator, since September 6, 2008. See “Note 1, Summary of Significant Accounting Policies” in our annual report on Form 10-K for the year ended December 31, 2017 (“2017 Form 10-K”) for additional information on our conservatorship and the impact of U.S. government support of our business. The unaudited interim condensed consolidated financial statements as of and for the three months ended March 31, 2018, and related notes, should be read in conjunction with our audited consolidated financial statements and related notes included in our 2017 Form 10-K. Basis of Presentation The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information and with the SEC’s instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and note disclosures required by GAAP for complete consolidated financial statements. In the opinion of management, all adjustments of a normal recurring nature considered necessary for a fair presentation have been included. The accompanying condensed consolidated financial statements include our accounts as well as the accounts of other entities in which we have a controlling financial interest. All intercompany accounts and transactions have been eliminated. To conform to our current period presentation, we have reclassified certain amounts reported in our prior periods’ condensed consolidated financial statements. Results for the three months ended March 31, 2018 may not necessarily be indicative of the results for the year ending December 31, 2018. Cash, Cash Equivalents and Restricted Cash On January 1, 2018, we adopted new accounting guidance that requires us to include in total cash and cash equivalents on the statement of cash flows the cash and cash equivalents that have restrictions on withdrawal or use. This guidance was applied retrospectively to the statement of cash flows for the prior period presented. As a result of this adoption, the net change in restricted cash that results from transfers between cash, cash equivalents, and restricted cash will no longer be presented as an investing activity in our condensed consolidated statement of cash flows. Additionally, we adopted new accounting guidance that clarified the classification of certain cash receipts and cash payments. This guidance was applied retrospectively to the statement of cash flows for the prior period presented. The adoption did not have a material impact to our statement of cash flows. Reclassification to Retained Earnings Resulting from the Enactment of the Tax Act In February 2018, the Financial Accounting Standards Board (“FASB”) issued guidance allowing a reclassification from accumulated other comprehensive income to retained earnings for stranded tax amounts resulting from the enactment of the Tax Cuts and Jobs Act of 2017 (“Tax Act”). GAAP requires the effect of changes in tax laws or rates on deferred taxes to be included in continuing operations in the reporting period that includes the enactment date. This applies even in situations in which the initial tax effects were recognized directly in other comprehensive income at a historical corporate income tax rate resulting in stranded tax amounts in accumulated other comprehensive income related to the corporate income tax rate differential. The guidance is effective beginning for fiscal years beginning January 1, 2019 and early adoption is permitted. We have elected to early adopt the guidance by reclassifying such stranded tax amounts, which were $117 million as of January 1, 2018, from accumulated other comprehensive income to retained earnings. Use of Estimates Preparing condensed consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect our reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities as of the dates of our condensed consolidated financial statements, as well as our reported amounts of revenues and expenses during the reporting periods. Management has made significant estimates in a variety of areas including, but not limited to, valuation of certain financial instruments and allowance for loan losses. Actual results could be different from these estimates. Senior Preferred Stock Purchase Agreement and Senior Preferred Stock Treasury has made a commitment under the senior preferred stock purchase agreement to provide funding to us under certain circumstances if we have a net worth deficit. On March 30, 2018, we received $3.7 billion from Treasury to eliminate our net worth deficit as of December 31, 2017. Pursuant to the senior preferred stock purchase agreement, we have received a total of $119.8 billion from Treasury as of March 31, 2018, and the amount of remaining funding available to us under the agreement was $113.9 billion. Because we had a positive net worth of $3.9 billion as of March 31, 2018, we will not be required to draw additional funds from Treasury pursuant to the senior preferred stock purchase agreement for this quarter. Pursuant to the senior preferred stock purchase agreement, we issued shares of senior preferred stock to Treasury in 2008. Acting as successor to the rights, titles, powers and privileges of the Board, our conservator has declared and directed us to pay dividends to Treasury on the senior preferred stock on a quarterly basis for every dividend period for which dividends were payable since we entered into conservatorship in 2008. Effective January 1, 2018, the dividend provisions of the senior preferred stock provide for quarterly dividends consisting of the amount, if any, by which our net worth as of the end of the immediately preceding fiscal quarter exceeds a $3.0 billion capital reserve amount. We refer to this as a “net worth sweep” dividend. Because we had a net worth deficit as of December 31, 2017, no dividend was payable to Treasury on the senior preferred stock for the first quarter of 2018. Because we had a positive net worth of $3.9 billion as of March 31, 2018, we expect to pay Treasury a dividend of $938 million for the second quarter of 2018 by June 30, 2018. The liquidation preference of the senior preferred stock is subject to adjustment. The aggregate liquidation preference of the senior preferred stock was $123.8 billion as of March 31, 2018. See “Note 11, Equity (Deficit)” in our 2017 Form 10-K for additional information about the senior preferred stock purchase agreement and the senior preferred stock. Regulatory Capital We submit capital reports to FHFA, which monitors our capital levels. The deficit of core capital over statutory minimum capital was $140.2 billion as of March 31, 2018 and $144.4 billion as of December 31, 2017. Due to the terms of our senior preferred stock described above, we do not expect to eliminate our deficit of core capital over statutory minimum capital. Related Parties As a result of our issuance to Treasury of the warrant to purchase shares of Fannie Mae common stock equal to 79.9% of the total number of shares of Fannie Mae common stock, we and Treasury are deemed related parties. As of March 31, 2018, Treasury held an investment in our senior preferred stock with an aggregate liquidation preference of $123.8 billion. FHFA’s control of Fannie Mae and Freddie Mac has caused Fannie Mae, FHFA and Freddie Mac to be deemed related parties. In 2013, Fannie Mae and Freddie Mac established Common Securitization Solutions, LLC (“CSS”), a jointly owned limited liability company to operate a common securitization platform; therefore, CSS is deemed a related party. Transactions with Treasury Our administrative expenses were reduced by $7 million and $12 million for the three months ended March 31, 2018 and March 31, 2017, respectively, due to reimbursements from Treasury and Freddie Mac for expenses incurred as program administrator for Treasury’s Home Affordable Modification Program and other initiatives under Treasury’s Making Home Affordable Program. During the three months ended March 31, 2018 and 2017, we did not make any payments to the Internal Revenue Service (“IRS”), a bureau of Treasury. In 2009, we entered into a memorandum of understanding with Treasury, FHFA and Freddie Mac pursuant to which we agreed to provide assistance to state and local housing finance agencies (“HFAs”) through certain programs, including a new issue bond (“NIB”) program. As of March 31, 2018, under the NIB program, Fannie Mae and Freddie Mac had $4.8 billion outstanding of pass-through securities backed by single-family and multifamily housing bonds issued by HFAs, which is less than 35% of the total original principal under the program, the amount of losses that Treasury would bear. Accordingly, we do not have a potential risk of loss under the NIB program. The fee revenue and expense related to the TCCA are recorded in “Mortgage loans interest income” and “TCCA fees,” respectively, in our condensed consolidated statements of operations and comprehensive income. We recognized $557 million and $503 million in TCCA fees during the three months ended March 31, 2018 and 2017, respectively, of which $557 million had not been remitted to Treasury as of March 31, 2018. We incurred expenses in connection with certain funding obligations under the Federal Housing Enterprises Financial Safety and Soundness Act of 1992, as amended by the Federal Housing Finance Regulatory Reform Act of 2008 (the “GSE Act”), a portion of which is attributable to Treasury’s Capital Magnet Fund. These expenses, recognized in “Other expenses, net” in our condensed consolidated statements of operations and comprehensive income, were measured as the product of 4.2 basis points and the unpaid principal balance of our total new business purchases for the respective period. We recognized $18 million and $15 million in “Other expenses, net” in connection with Treasury’s Capital Magnet Fund for the three months ended March 31, 2018 and 2017, respectively, of which $18 million had not been remitted as of March 31, 2018. In addition to the transactions with Treasury mentioned above, we purchase and sell Treasury securities in the normal course of business. As of March 31, 2018 and December 31, 2017, we held Treasury securities with a fair value of $33.2 billion and $29.2 billion, respectively, and accrued interest receivable of $87 million and $77 million, respectively. We recognized interest income on these securities held by us of $129 million and $63 million for the three months ended March 31, 2018 and 2017, respectively. Transactions with Freddie Mac As of March 31, 2018 and December 31, 2017, we held Freddie Mac mortgage-related securities with a fair value of $579 million and $613 million, respectively, and accrued interest receivable of $2 million. We recognized interest income on these securities held by us of $7 million and $13 million for the three months ended March 31, 2018 and 2017, respectively. In addition, Freddie Mac may be an investor in variable interest entities (“VIEs”) that we have consolidated, and we may be an investor in VIEs that Freddie Mac has consolidated. Freddie Mac may also be an investor in our debt securities. Transactions with FHFA The GSE Act authorizes FHFA to establish an annual assessment for regulated entities, including Fannie Mae, which is payable on a semi-annual basis (April and October), for FHFA’s costs and expenses, as well as to maintain FHFA’s working capital. We recognized FHFA assessment fees, which are recorded in “Administrative expenses” in our condensed consolidated statements of operations and comprehensive income, of $29 million and $30 million for the three months ended March 31, 2018 and 2017, respectively. Transactions with CSS In connection with our jointly owned company with Freddie Mac, we contributed capital to CSS of $41 million and $35 million for the three months ended March 31, 2018 and 2017, respectively. No other transactions outside of normal business activities have occurred between us and CSS during the three months ended March 31, 2018 and 2017. Income Taxes The decrease in our provision for federal income taxes for the three months ended March 31, 2018 as compared to the three months ended March 31, 2017 was the result of the Tax Act, which reduced the federal corporate income tax rate from 35% to 21% effective January 1, 2018. This decline in the federal corporate income tax rate was the primary driver of the reduction in our effective tax rate to 21.0% for the three months ended March 31, 2018, compared with 33.3% for the same period in 2017. Earnings (Loss) per Share Earnings (loss) per share (“EPS”) is presented for basic and diluted EPS. We compute basic EPS by dividing net income (loss) attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period. However, as a result of our conservatorship status and the terms of the senior preferred stock, no amounts are available to distribute as dividends to common or preferred stockholders (other than to Treasury as holder of the senior preferred stock). Weighted average common shares includes 4.6 billion shares for the periods ended March 31, 2018 and 2017 that would be issued upon the full exercise of the warrant issued to Treasury from the date the warrant was issued through March 31, 2018 and 2017. The calculation of diluted EPS includes all the components of basic earnings per share, plus the dilutive effect of common stock equivalents such as convertible securities and stock options. Weighted average shares outstanding is increased to include the number of additional common shares that would have been outstanding if the dilutive potential common shares had been issued. Our diluted EPS weighted average shares outstanding includes 131 million shares of convertible preferred stock for the quarter ended March 31, 2018. For the quarter ended March 31, 2017, convertible preferred stock is not included in the calculation because a net loss attributable to common stockholders was incurred and it would have an anti-dilutive effect. New Accounting Guidance In January 2016, the FASB issued guidance, which we adopted on January 1, 2018, that amends certain aspects of recognition, measurement, presentation and disclosure of financial instruments. The adoption of these amendments did not have a material effect on our condensed consolidated financial statements. In June 2016, the FASB issued guidance that changes the impairment model for most financial assets and certain other instruments. For loans, held-to-maturity debt securities and other financial assets recorded at amortized cost, entities will be required to use a new forward-looking “expected loss” model that will replace today’s “incurred loss” model and generally will result in the earlier recognition of allowance for loan losses. The guidance is effective on January 1, 2020 with early adoption permitted on January 1, 2019. We will adopt the standard on January 1, 2020. We will recognize the impact of the new guidance through a cumulative effect adjustment to retained earnings as of the beginning of the year of adoption. We are continuing to evaluate the impact of this guidance on our condensed consolidated financial statements. We expect the greater impact of the guidance to relate to our accounting for credit losses for loans that are not individually impaired. The adoption of this guidance may decrease, perhaps substantially, our retained earnings and increase our allowance for loan losses.