Conservatorship, Senior Preferred Stock Purchase Agreement and Related Matters - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2008	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Mar. 31, 2024	Sep. 07, 2008
Related Parties [Line Items]
Adjusted total assets			$ 136,600
Capital deficit			(74,000)	$ (93,000)
Preferred stock, covenant, maximum mortgage assets			225,000
FHFA debt limit			270,000
Suspended maximum single-family loans for cash consideration from any one single seller			1,500
Suspended maximum multifamily mortgage assets			$ 80,000
Suspended minimum percentage of multifamily acquisitions classified as mission driven			50.00%
Suspended maximum percentage of single-family loans resulting from refinancing			3.00%
Suspended maximum percentage of single-family loans not resulting from refinancing			6.00%
Maximum combined LTV ratio of single-family loans acquired not resulting from refinancing			90.00%
Minimum income ratio of single-family loans acquired not resulting from refinancing			45.00%
Suspended maximum percentage of single-family loans secured by second homes or investment properties			7.00%
TCCA fees			$ 3,431	3,369	$ 3,071
Basis points of each dollar of unpaid principal balance			0.042%
Affordable Housing Program obligation			35.00%
Fannie Mae
Related Parties [Line Items]
Preferred stock, covenant, maximum mortgage assets			$ 202,500
Series 2008-2 Senior Preferred Stock
Related Parties [Line Items]
Stock issued (in shares)	1
Value assigned to Treasury's commitment and recorded as a reduction to additional paid-in-capital	$ 4,500
Preferred stock covenant maximum fair market value of assets and properties per transaction			250
Aggregate liquidation preference of senior preferred stock			1,000
US Treasury and Government
Related Parties [Line Items]
Aggregate funding received from US Treasury pursuant to the senior preferred stock purchase agreement			119,800
US Treasury
Related Parties [Line Items]
Percentage of common shares attributable to warrants	79.90%						79.90%
Common stock warrant exercise price (in dollars per share)	$ 0.00001
Aggregate funding received from US Treasury pursuant to the senior preferred stock purchase agreement			119,800
Total available funding from treasury pursuant to the senior preferred stock agreement			113,900
Aggregate liquidation preference of senior preferred stock			195,200
Home Affordable Modification Program administrative expense reimbursement			$ 6	15	17
TCCA, increase of guarantee fee rate			0.10%
TCCA fees			$ 3,431	3,369	3,071
US Treasury | Other Expense
Related Parties [Line Items]
Affordable Housing Program assessments			54	101	209
Payments to Treasury's Capital Magnet Fund			101	209
US Treasury | Single-Family
Related Parties [Line Items]
Recognized TCCA fees that had not been remitted to Treasury as of period end			861	854
US Treasury | Forecast
Related Parties [Line Items]
Aggregate liquidation preference of senior preferred stock						$ 199,200
US Treasury | Forecast | Other Expense
Related Parties [Line Items]
Affordable Housing Program assessments		$ 54
Federal Housing Finance Agency
Related Parties [Line Items]
FHFA assessment fees/expense			159	132	140
Common Securitization Solutions
Related Parties [Line Items]
Payments to acquire equity method investments			$ 72	$ 65	$ 76