Allowance for Credit Losses - Changes in Allowance (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Total allowance for credit losses:
Beginning balance	$ (8,753)	$ (8,471)	$ (8,592)	$ (7,886)
(Provision) benefit for credit losses	(1,140)	(338)	(1,902)	(1,308)
Write-offs	341	408	1,150	948
Recoveries	(107)	(76)	(315)	(231)
Ending balance	(9,659)	(8,477)	(9,659)	(8,477)
Single-family
Total allowance for credit losses:
Beginning balance	(6,345)	(5,985)	(6,272)	(5,487)
(Provision) benefit for credit losses	(694)	(269)	(1,023)	(1,030)
Write-offs	181	241	546	598
Recoveries	(67)	(51)	(176)	(145)
Ending balance	(6,925)	(6,064)	(6,925)	(6,064)
Multifamily
Total allowance for credit losses:
Beginning balance	(2,408)	(2,486)	(2,320)	(2,399)
(Provision) benefit for credit losses	(446)	(69)	(879)	(278)
Write-offs	160	167	604	350
Recoveries	(40)	(25)	(139)	(86)
Ending balance	$ (2,734)	$ (2,413)	$ (2,734)	$ (2,413)