Mortgage Loans - Non-accrual Loans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	$ 29,035	$ 26,215	$ 29,035	$ 26,215	$ 29,563	$ 29,101	$ 25,336	$ 25,205
Total interest income recognized	52	39	331	311
Single-family
Financing Receivable, Nonaccrual [Line Items]
Accrued interest receivable written off through the reversal of interest income:	101	95	295	274
Recorded investment in nonaccrual loans	26,141	23,956	26,141	23,956	26,701	26,584	23,500	23,315
Total interest income recognized	47	37	308	276
Single-family | 20- and 30-year or more, amortizing fixed-rate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	24,936	22,662	24,936	22,662	25,423	25,218	22,183	21,971
Total interest income recognized	45	35	295	262
Single-family | 15-year or less, amortizing fixed-rate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	689	704	689	704	736	770	704	727
Total interest income recognized	1	1	6	6
Single-family | Adjustable-rate
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	108	110	108	110	114	114	117	109
Total interest income recognized	0	0	2	1
Single-family | Other
Financing Receivable, Nonaccrual [Line Items]
Recorded investment in nonaccrual loans	408	480	408	480	428	482	496	508
Total interest income recognized	1	1	5	7
Multifamily
Financing Receivable, Nonaccrual [Line Items]
Accrued interest receivable written off through the reversal of interest income:	11	20	25	24
Recorded investment in nonaccrual loans	2,894	2,259	2,894	2,259	$ 2,862	$ 2,517	$ 1,836	$ 1,890
Total interest income recognized	$ 5	$ 2	$ 23	$ 35