Mortgage Loans - Non-accrual Loans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	$ 26,215	$ 21,897	$ 26,215	$ 21,897	$ 25,336	$ 25,205	$ 19,722	$ 12,517
Total interest income recognized	39	23	311	224
Single-family
Financing Receivable, Nonaccrual [Line Items]
Accrued interest receivable written off through the reversal of interest income:	95	80	274	233
Recorded investment in nonaccrual loans	23,956	20,371	23,956	20,371	23,500	23,315	18,274	10,317
Total interest income recognized	37	20	276	208
Single-family | 20- and 30-year or more, amortizing fixed-rate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	22,662	19,108	22,662	19,108	22,183	21,971	17,051	9,447
Total interest income recognized	35	19	262	197
Single-family | 15-year or less, amortizing fixed-rate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	704	638	704	638	704	727	565	200
Total interest income recognized	1	0	6	4
Single-family | Adjustable-rate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	110	99	110	99	117	109	85	53
Total interest income recognized	0	0	1	1
Single-family | Other
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	480	526	480	526	496	508	573	617
Total interest income recognized	1	1	7	6
Multifamily
Financing Receivable, Nonaccrual [Line Items]
Accrued interest receivable written off through the reversal of interest income:	20	3	24	36
Recorded investment in nonaccrual loans	2,259	1,526	2,259	1,526	$ 1,836	$ 1,890	$ 1,448	$ 2,200
Total interest income recognized	$ 2	$ 3	$ 35	$ 16