Allowance for Loan Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for Loan Losses [Roll Forward]
Beginning balance	$ (11,347)	$ (5,629)	$ (10,552)
Benefit (provision) for loan losses	1,582	(6,306)	5,022
Write-offs	1,274	926	476
Recoveries	(262)	(299)	(468)
Other	23	(39)	(107)
Ending balance	(8,730)	(11,347)	(5,629)
Unpaid principal balance of mortgage loans	4,102,632	4,075,598
Multifamily
Allowance for Loan Losses [Roll Forward]
Unpaid principal balance of mortgage loans	461,247	431,440
Multifamily | Seniors housing portfolio
Allowance for Loan Losses [Roll Forward]
Unpaid principal balance of mortgage loans		$ 16,600
Multifamily | Seniors housing portfolio | Adjustable-rate
Allowance for Loan Losses [Roll Forward]
Percentage of book of business		39.00%
Single-family
Allowance for Loan Losses [Roll Forward]
Amortized cost	3,334	$ 7,825	16,606
Related allowance	42	373	1,605
Unpaid principal balance of mortgage loans	3,641,385	3,644,158
Single-family
Allowance for Loan Losses [Roll Forward]
Beginning balance	(9,443)	(4,950)	(9,344)
Benefit (provision) for loan losses	2,079	(5,061)	4,503
Write-offs	873	883	417
Recoveries	(203)	(276)	(419)
Other	23	(39)	(107)
Ending balance	(6,671)	(9,443)	(4,950)
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	(1,904)	(679)	(1,208)
Benefit (provision) for loan losses	(497)	(1,245)	519
Write-offs	401	43	59
Recoveries	(59)	(23)	(49)
Ending balance	$ (2,059)	$ (1,904)	$ (679)