Conservatorship, Senior Preferred Stock Purchase Agreement and Related Matters - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		1 Months Ended
	Sep. 08, 2008	Sep. 30, 2008	Dec. 31, 2024	Dec. 31, 2023	Sep. 07, 2008
Related Parties [Line Items]
Preferred stock, covenant, maximum mortgage assets			$ 225,000
FHFA debt limit			$ 270,000
Basis points of each dollar of unpaid principal balance			0.042%
Affordable Housing Program obligation			35.00%
Other liabilities (includes $1,699 and $1,713, respectively, related to consolidated trusts)			$ 15,392	$ 14,106
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
Preferred stock covenant maximum fair market value of assets and properties per transaction			250
Aggregate liquidation preference of senior preferred stock			1,000
Related Party | 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
Value assigned to Treasury's commitment and recorded as a reduction to additional paid-in-capital		$ 4,500
Fair value of the warrant at issuance	$ 3,500
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			212,000
Related Party | Treasury | TCCA fees
Related Parties [Line Items]
Other liabilities (includes $1,699 and $1,713, respectively, related to consolidated trusts)			861	861
Related Party | Treasury | Treasury’s Capital Magnet Fund
Related Parties [Line Items]
Other liabilities (includes $1,699 and $1,713, respectively, related to consolidated trusts)			56	54
Related Party | FHFA
Related Parties [Line Items]
Other liabilities (includes $1,699 and $1,713, respectively, related to consolidated trusts)			0	0
Related Party | Treasury & Freddie Mac
Related Parties [Line Items]
Other liabilities (includes $1,699 and $1,713, respectively, related to consolidated trusts)			0	0
Related Party | CSS & Freddie Mac
Related Parties [Line Items]
Other liabilities (includes $1,699 and $1,713, respectively, related to consolidated trusts)			0	$ 0
Treasury
Related Parties [Line Items]
Aggregate funding received from US Treasury pursuant to the senior preferred stock purchase agreement			119,800
Aggregate liquidation preference of senior preferred stock			$ 216,100
TCCA, increase of guarantee fee rate			0.10%