Summary of Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation [Policy Text Block]	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 period condensed consolidated financial statements. Results for the three and six months ended June 30, 2019 may not necessarily be indicative of the results for the year ending December 31, 2019.
Use of Estimates, Policy [Policy Text Block]	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, 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, the allowance for loan losses. Actual results could be different from these estimates.
Earnings Per Share, Policy [Policy Text Block]	Earnings per share (“EPS”) is presented for basic and diluted EPS. We compute basic EPS by dividing net income 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 would be available to distribute as dividends to common or preferred stockholders (other than to Treasury as the holder of the senior preferred stock). Weighted average common shares includes 4.6 billion shares for the periods ended June 30, 2019 and 2018 that would be issued upon the full exercise of the warrant issued to Treasury from the date the warrant was issued through June 30, 2019 and 2018. 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. For the three months ended June 30, 2019 and six months ended June 30, 2019 and 2018, our diluted EPS weighted average shares outstanding includes shares of common stock that would be issuable upon the conversion of 131 million shares of convertible preferred stock. For the three months ended June 30, 2018, convertible preferred stock is not included in the calculation because a net loss attributable to common shareholders was incurred and it would have an anti-dilutive effect.
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Guidance The following updates information about our significant accounting policies that have recently been adopted or yet to be adopted from the information included in “Note 1, Summary of Significant Accounting Policies” in our 2018 Form 10-K. The Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments (“CECL”) in June 2016. It was amended by ASU 2019-04, Codification Improvements (to Topic 326), Financial Instruments—Credit Losses in April 2019. The standard replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects lifetime expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The amendments in this standard also require credit losses related to available-for-sale debt securities to be recorded through an allowance for credit losses. We do not expect a material impact for establishing an allowance for credit losses related to our available-for-sale debt securities. CECL will become effective for our fiscal year beginning January 1, 2020. We are continuing to update the allowance models and accounting systems that will be used to estimate credit losses and record accounting impacts under CECL, and we are in the process of validating their results. All updates to our allowance models are subject to our model oversight and review governance process. We expect model and system testing to continue in 2019, followed by full integrated testing across all affected systems and processes. We are managing the implementation of this guidance in accordance with our change management governance standards, which are designed to ensure compliance with GAAP as well as operational readiness at adoption. Senior management and the Audit Committee receive regular updates regarding the status of our implementation plan, results of modeled impacts and any identified key risks. We will use a discounted cash flow method to measure credit impairment on our single-family mortgage loans and an undiscounted loss method to measure credit impairment on our multifamily mortgage loans. The models we will use to estimate credit losses will incorporate our historical credit loss experience, adjusted for current economic forecasts and the current credit profile of our loan book of business. The models will use reasonable and supportable forecasts for key economic drivers, such as home prices (Single-Family), rental income (Multifamily) and capitalization rates (Multifamily). Based on the composition of the loans in our book of business as of June 30, 2019 and our current expectations of future economic conditions, we estimate that our adoption of CECL will result in a reduction in our retained earnings of up to $4 billion on an after-tax basis in the first quarter of 2020. We are still assessing the impact of various implementation issues as well as the FASB’s recently proposed guidance relating to the standard. The resolution of these items may reduce CECL’s impact on our retained earnings upon adoption. In addition, we continue to evaluate the results of our modeled loss estimates and may make refinements to our approach and assumptions. The impact of our adoption of CECL on our retained earnings will be further influenced by the credit risk profile of the loans in our book of business as of the January 1, 2020 adoption date, as well as economic conditions and forecasts of future economic conditions at that time.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2019

Basis of Presentation [Policy Text Block]

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 period condensed consolidated financial statements. Results for the three and six months ended June 30, 2019 may not necessarily be indicative of the results for the year ending December 31, 2019.

Use of Estimates, Policy [Policy Text Block]

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, 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, the allowance for loan losses. Actual results could be different from these estimates.

Earnings Per Share, Policy [Policy Text Block]

Earnings per share (“EPS”) is presented for basic and diluted EPS. We compute basic EPS by dividing net income 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 would be available to distribute as dividends to common or preferred stockholders (other than to Treasury as the holder of the senior preferred stock). Weighted average common shares includes 4.6 billion shares for the periods ended June 30, 2019 and 2018 that would be issued upon the full exercise of the warrant issued to Treasury from the date the warrant was issued through June 30, 2019 and 2018.

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. For the three months ended June 30, 2019 and six months ended June 30, 2019 and 2018, our diluted EPS weighted average shares outstanding includes shares of common stock that would be issuable upon the conversion of 131 million shares of convertible preferred stock. For the three months ended June 30, 2018, convertible preferred stock is not included in the calculation because a net loss attributable to common shareholders was incurred and it would have an anti-dilutive effect.

New Accounting Pronouncements, Policy [Policy Text Block]

New Accounting Guidance

The following updates information about our significant accounting policies that have recently been adopted or yet to be adopted from the information included in “Note 1, Summary of Significant Accounting Policies” in our 2018 Form 10-K.

The Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments (“CECL”) in June 2016. It was amended by ASU 2019-04, Codification Improvements (to Topic 326), Financial Instruments—Credit Losses in April 2019. The standard replaces the incurred loss impairment methodology in current GAAP with a methodology that reflects lifetime expected credit losses and requires consideration of a broader range of reasonable and supportable information to inform credit loss estimates. The amendments in this standard also require credit losses related to available-for-sale debt securities to be recorded through an allowance for credit losses. We do not expect a material impact for establishing an allowance for credit losses related to our available-for-sale debt securities.

CECL will become effective for our fiscal year beginning January 1, 2020. We are continuing to update the allowance models and accounting systems that will be used to estimate credit losses and record accounting impacts under CECL, and we are in the process of validating their results. All updates to our allowance models are subject to our model oversight and review governance process. We expect model and system testing to continue in 2019, followed by full integrated testing across all affected systems and processes. We are managing the implementation of this guidance in accordance with our change management governance standards, which are designed to ensure compliance with GAAP as well as operational readiness at adoption. Senior management and the Audit Committee receive regular updates regarding the status of our implementation plan, results of modeled impacts and any identified key risks.

We will use a discounted cash flow method to measure credit impairment on our single-family mortgage loans and an undiscounted loss method to measure credit impairment on our multifamily mortgage loans. The models we will use to estimate credit losses will incorporate our historical credit loss experience, adjusted for current economic forecasts and the current credit profile of our loan book of business. The models will use reasonable and supportable forecasts for key economic drivers, such as home prices (Single-Family), rental income (Multifamily) and capitalization rates (Multifamily).

Based on the composition of the loans in our book of business as of June 30, 2019 and our current expectations of future economic conditions, we estimate that our adoption of CECL will result in a reduction in our retained earnings of up to $4 billion on an after-tax basis in the first quarter of 2020. We are still assessing the impact of various implementation issues as well as the FASB’s recently proposed guidance relating to the standard. The resolution of these items may reduce CECL’s impact on our retained earnings upon adoption. In addition, we continue to evaluate the results of our modeled loss estimates and may make refinements to our approach and assumptions. The impact of our adoption of CECL on our retained earnings will be further influenced by the credit risk profile of the loans in our book of business as of the January 1, 2020 adoption date, as well as economic conditions and forecasts of future economic conditions at that time.