Allowance for Loan Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	$ (5,899)	$ (9,628)	$ (5,629)	$ (10,552)
Benefit (provision) for loan losses	(260)	2,528	(514)	3,294
Write-offs	248	163	275	267
Recoveries	(94)	(95)	(134)	(98)
Other	(64)	(82)	(67)	(25)
Ending Balance	(6,069)	(7,114)	(6,069)	(7,114)
Single-family
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	(5,241)	(8,547)	(4,950)	(9,344)
Benefit (provision) for loan losses	(248)	2,493	(530)	3,164
Write-offs	248	149	275	220
Recoveries	(84)	(77)	(117)	(79)
Other	(64)	(82)	(67)	(25)
Ending Balance	(5,389)	(6,064)	(5,389)	(6,064)
Multifamily
Financing Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	(658)	(1,081)	(679)	(1,208)
Benefit (provision) for loan losses	(12)	35	16	130
Write-offs	0	14	0	47
Recoveries	(10)	(18)	(17)	(19)
Ending Balance	$ (680)	$ (1,050)	$ (680)	$ (1,050)