Allowance for Loan Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for Loan Losses [Roll Forward]
Beginning balance	$ (10,552)	$ (9,016)	$ (14,203)
Benefit (provision) for loan losses	5,022	(466)	3,961
Write-offs	476	593	1,307
Recoveries	(468)	(94)	(75)
Other	(107)	153	(6)
Ending balance	(5,629)	(10,552)	(9,016)
Transition impact of the adoption of the CECL standard
Allowance for Loan Losses [Roll Forward]
Beginning balance	0	(1,722)
Ending balance		0	(1,722)
Single-family
Allowance for Loan Losses [Roll Forward]
Beginning balance	(9,344)	(8,759)	(13,969)
Benefit (provision) for loan losses	4,503	127	3,988
Write-offs	417	457	1,299
Recoveries	(419)	(93)	(71)
Other	(107)	153	(6)
Ending balance	(4,950)	(9,344)	(8,759)
Single-family | Transition impact of the adoption of the CECL standard
Allowance for Loan Losses [Roll Forward]
Beginning balance	0	(1,229)
Ending balance		0	(1,229)
Multifamily
Allowance for Loan Losses [Roll Forward]
Beginning balance	(1,208)	(257)	(234)
Benefit (provision) for loan losses	519	(593)	(27)
Write-offs	59	136	8
Recoveries	(49)	(1)	(4)
Ending balance	(679)	(1,208)	(257)
Multifamily | Transition impact of the adoption of the CECL standard
Allowance for Loan Losses [Roll Forward]
Beginning balance	$ 0	(493)
Ending balance		$ 0	$ (493)