Mortgage Loans - Aging (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 4,144,227	$ 4,149,258
Loans 90 Days or More Delinquent and Accruing Interest	748	1,775
Nonaccrual Loans with No Allowance	$ 4,061	4,476
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	$ 64,552	66,479
30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	37,138	36,184
60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	8,183	8,625
Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	19,231	21,670
Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	4,079,675	4,082,779
Single-family
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,673,361	3,687,904
Loans 90 Days or More Delinquent and Accruing Interest	642	1,604
Nonaccrual Loans with No Allowance	$ 3,510	$ 3,882
Single-family | Minimum
Table Footnote [Abstract]
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	$ 62,053	$ 64,331
Single-family | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	36,203	35,735
Single-family | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	8,183	8,625
Single-family | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	17,667	19,971
Single-family | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,611,308	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	3,226,616	3,208,042
Loans 90 Days or More Delinquent and Accruing Interest	568	1,371
Nonaccrual Loans with No Allowance	3,128	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	57,965	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	33,669	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	7,696	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	16,600	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	3,168,651	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	398,163	428,413
Loans 90 Days or More Delinquent and Accruing Interest	34	74
Nonaccrual Loans with No Allowance	188	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	2,609	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	1,775	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	288	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	546	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	395,554	425,598
Single-family | Adjustable-rate
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	25,923	26,358
Loans 90 Days or More Delinquent and Accruing Interest	3	11
Nonaccrual Loans with No Allowance	15	21
Single-family | Adjustable-rate | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	304	326
Single-family | Adjustable-rate | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	176	184
Single-family | Adjustable-rate | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	38	42
Single-family | Adjustable-rate | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	90	100
Single-family | Adjustable-rate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	25,619	26,032
Single-family | Other
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	22,659	25,091
Loans 90 Days or More Delinquent and Accruing Interest	37	148
Nonaccrual Loans with No Allowance	179	228
Single-family | Other | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	1,175	1,319
Single-family | Other | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	583	586
Single-family | Other | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	161	171
Single-family | Other | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	431	562
Single-family | Other | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	21,484	23,772
Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	470,866	461,354
Loans 90 Days or More Delinquent and Accruing Interest	106	171
Nonaccrual Loans with No Allowance	$ 551	594
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	$ 2,499	2,148
Multifamily | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	935	449
Multifamily | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	1,564	1,699
Multifamily | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 468,367	$ 459,206