Mortgage Loans - Aging Analysis (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 4,152,406	$ 4,149,258
Loans 90 Days or More Delinquent and Accruing Interest	445	1,775
Nonaccrual Loans with No Allowance	$ 5,270	4,476
Table Footnote
Serious delinquency: days past due	90 days
Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 70,322	66,479
30-59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	37,021	36,184
60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	10,122	8,625
Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	23,179	21,670
Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	4,082,084	4,082,779
Single-family
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,662,679	3,687,904
Loans 90 Days or More Delinquent and Accruing Interest	369	1,604
Nonaccrual Loans with No Allowance	4,200	3,882
Table Footnote
Mortgage loans in process of foreclosure	$ 4,700	$ 4,600
Single-family | Minimum
Table Footnote
Serious delinquency: days past due	90 days	90 days
Single-family | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 67,771	$ 64,331
Single-family | 30-59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	36,530	35,735
Single-family | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	10,122	8,625
Single-family | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	21,119	19,971
Single-family | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,594,908	3,623,573
Single-family | 20- and 30-year or more, amortizing fixed-rate
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,247,328	3,208,042
Loans 90 Days or More Delinquent and Accruing Interest	329	1,371
Nonaccrual Loans with No Allowance	3,790	3,457
Single-family | 20- and 30-year or more, amortizing fixed-rate | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	63,925	59,871
Single-family | 20- and 30-year or more, amortizing fixed-rate | 30-59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	34,339	33,119
Single-family | 20- and 30-year or more, amortizing fixed-rate | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	9,582	8,093
Single-family | 20- and 30-year or more, amortizing fixed-rate | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	20,004	18,659
Single-family | 20- and 30-year or more, amortizing fixed-rate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,183,403	3,148,171
Single-family | 15-year or less, amortizing fixed-rate
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	369,727	428,413
Loans 90 Days or More Delinquent and Accruing Interest	16	74
Nonaccrual Loans with No Allowance	208	176
Single-family | 15-year or less, amortizing fixed-rate | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	2,513	2,815
Single-family | 15-year or less, amortizing fixed-rate | 30-59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	1,545	1,846
Single-family | 15-year or less, amortizing fixed-rate | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	352	319
Single-family | 15-year or less, amortizing fixed-rate | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	616	650
Single-family | 15-year or less, amortizing fixed-rate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	367,214	425,598
Single-family | Adjustable-rate
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	25,018	26,358
Loans 90 Days or More Delinquent and Accruing Interest	3	11
Nonaccrual Loans with No Allowance	18	21
Single-family | Adjustable-rate | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	295	326
Single-family | Adjustable-rate | 30-59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	158	184
Single-family | Adjustable-rate | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	45	42
Single-family | Adjustable-rate | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	92	100
Single-family | Adjustable-rate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	24,723	26,032
Single-family | Other
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	20,606	25,091
Loans 90 Days or More Delinquent and Accruing Interest	21	148
Nonaccrual Loans with No Allowance	184	228
Single-family | Other | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	1,038	1,319
Single-family | Other | 30-59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	488	586
Single-family | Other | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	143	171
Single-family | Other | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	407	562
Single-family | Other | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	19,568	23,772
Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	489,727	461,354
Loans 90 Days or More Delinquent and Accruing Interest	76	171
Nonaccrual Loans with No Allowance	$ 1,070	$ 594
Multifamily | Minimum
Table Footnote
Serious delinquency: days past due	60 days	60 days
Multifamily | Maximum
Table Footnote
Serious delinquency: days past due	89 days	89 days
Multifamily | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 2,551	$ 2,148
Multifamily | 30-59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	491	449
Multifamily | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	2,060	1,699
Multifamily | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 487,176	$ 459,206