Mortgage Loans - Aging (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 4,136,980	$ 4,152,406
Loans 90 Days or More Delinquent and Accruing Interest	228	445
Nonaccrual Loans with No Allowance	$ 5,594	5,270
Table Footnote [Abstract]
Serious delinquency, days past due	90 days
Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 67,153	70,322
30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	34,601	37,021
60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	9,341	10,122
Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	23,211	23,179
Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	4,069,827	4,082,084
Single-family
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,626,030	3,662,679
Loans 90 Days or More Delinquent and Accruing Interest	227	369
Nonaccrual Loans with No Allowance	3,755	4,200
Table Footnote [Abstract]
Mortgage loans in process of foreclosure	$ 5,100	4,700
Single-family | Minimum
Table Footnote [Abstract]
Serious delinquency, days past due	90 days
Single-family | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 63,769	67,771
Single-family | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	33,996	36,530
Single-family | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	9,341	10,122
Single-family | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	20,432	21,119
Single-family | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,562,261	3,594,908
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	3,249,546	3,247,328
Loans 90 Days or More Delinquent and Accruing Interest	204	329
Nonaccrual Loans with No Allowance	3,426	3,790
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	60,413	63,925
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	32,049	34,339
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	8,895	9,582
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	19,469	20,004
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	3,189,133	3,183,403
Single-family | 15-year or less, amortizing fixed-rate
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	332,328	369,727
Loans 90 Days or More Delinquent and Accruing Interest	8	16
Nonaccrual Loans with No Allowance	188	208
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	2,162	2,513
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	1,346	1,545
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	276	352
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	540	616
Single-family | 15-year or less, amortizing fixed-rate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	330,166	367,214
Single-family | Adjustable-rate
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	25,902	25,018
Loans 90 Days or More Delinquent and Accruing Interest	1	3
Nonaccrual Loans with No Allowance	15	18
Single-family | Adjustable-rate | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	287	295
Single-family | Adjustable-rate | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	163	158
Single-family | Adjustable-rate | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	37	45
Single-family | Adjustable-rate | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	87	92
Single-family | Adjustable-rate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	25,615	24,723
Single-family | Other
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	18,254	20,606
Loans 90 Days or More Delinquent and Accruing Interest	14	21
Nonaccrual Loans with No Allowance	126	184
Single-family | Other | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	907	1,038
Single-family | Other | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	438	488
Single-family | Other | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	133	143
Single-family | Other | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	336	407
Single-family | Other | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	17,347	19,568
Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	510,950	489,727
Loans 90 Days or More Delinquent and Accruing Interest	1	76
Nonaccrual Loans with No Allowance	$ 1,839	1,070
Multifamily | Minimum
Table Footnote [Abstract]
Serious delinquency, days past due	60 days
Multifamily | Maximum
Table Footnote [Abstract]
Serious delinquency, days past due	89 days
Multifamily | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 3,384	2,551
Multifamily | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	605	491
Multifamily | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	2,779	2,060
Multifamily | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 507,566	$ 487,176