Mortgage Loans - Aging (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2026	Dec. 31, 2025
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 4,121,185	$ 4,133,279
Loans 90 Days or More Delinquent and Accruing Interest	172	209
Nonaccrual Loans with No Allowance	$ 6,366	6,041
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	$ 74,422	71,985
30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	37,781	36,206
60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	10,557	10,685
Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	26,084	25,094
Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	4,046,763	4,061,294
Single-family
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,587,155	3,609,326
Loans 90 Days or More Delinquent and Accruing Interest	103	191
Nonaccrual Loans with No Allowance	4,409	4,056
Table Footnote [Abstract]
Mortgage loans in process of foreclosure	$ 6,300	5,400
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	$ 71,069	68,226
Single-family | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	37,166	35,687
Single-family | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	10,557	10,685
Single-family | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	23,346	21,854
Single-family | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	3,516,086	3,541,100
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	3,241,898	3,240,510
Loans 90 Days or More Delinquent and Accruing Interest	90	171
Nonaccrual Loans with No Allowance	4,029	3,713
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	67,792	64,826
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	35,302	33,764
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	10,101	10,205
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	22,389	20,857
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	3,174,106	3,175,684
Single-family | 15-year or less, amortizing fixed-rate
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	294,100	322,584
Loans 90 Days or More Delinquent and Accruing Interest	3	7
Nonaccrual Loans with No Allowance	246	193
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	2,134	2,170
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	1,287	1,313
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	296	310
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	551	547
Single-family | 15-year or less, amortizing fixed-rate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	291,966	320,414
Single-family | Adjustable-rate
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	35,370	28,606
Loans 90 Days or More Delinquent and Accruing Interest	0	1
Nonaccrual Loans with No Allowance	15	17
Single-family | Adjustable-rate | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	313	294
Single-family | Adjustable-rate | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	175	155
Single-family | Adjustable-rate | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	46	43
Single-family | Adjustable-rate | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	92	96
Single-family | Adjustable-rate | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	35,057	28,312
Single-family | Other
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	15,787	17,626
Loans 90 Days or More Delinquent and Accruing Interest	10	12
Nonaccrual Loans with No Allowance	119	133
Single-family | Other | Total Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	830	936
Single-family | Other | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	402	455
Single-family | Other | 60 - 89 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	114	127
Single-family | Other | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	314	354
Single-family | Other | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	14,957	16,690
Multifamily
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	534,030	523,953
Loans 90 Days or More Delinquent and Accruing Interest	69	18
Nonaccrual Loans with No Allowance	$ 1,957	1,985
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	$ 3,353	3,759
Multifamily | 30 - 59 Days Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	615	519
Multifamily | Seriously Delinquent
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	2,738	3,240
Multifamily | Current
Financing Receivable, Past Due [Line Items]
Loans held for investment, excluding fair value option	$ 530,677	$ 520,194