Allowance for Loan Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Allowance for Loan Losses [Roll Forward]
Beginning balance	$ (8,730)	$ (11,347)	$ (5,629)
Benefit (provision) for loan losses	140	1,582	(6,306)
Write-offs	1,222	1,274	926
Recoveries	(339)	(262)	(299)
Other	0	23	(39)
Ending balance	(7,707)	(8,730)	(11,347)
Single-family
Allowance for Loan Losses [Roll Forward]
Amortized cost	2,329	3,334	7,825
Related allowance	21	42	373
Single-family
Allowance for Loan Losses [Roll Forward]
Beginning balance	(6,671)	(9,443)	(4,950)
Benefit (provision) for loan losses	888	2,079	(5,061)
Write-offs	717	873	883
Recoveries	(253)	(203)	(276)
Other	0	23	(39)
Ending balance	(5,319)	(6,671)	(9,443)
Amortized cost	3,300
Related allowance	42
Write-off against allowance	(658)
Additional provision for loan losses	(616)
Multifamily
Allowance for Loan Losses [Roll Forward]
Beginning balance	(2,059)	(1,904)	(679)
Benefit (provision) for loan losses	(748)	(497)	(1,245)
Write-offs	505	401	43
Recoveries	(86)	(59)	(23)
Ending balance	$ (2,388)	$ (2,059)	$ (1,904)