Mortgage Loans - Loan Restructuring - Aging Analysis (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 18,309	$ 21,036
Serious delinquency, days past due	90 days
Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 38,924	37,931
30 - 59 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	4,489	4,203
60 - 89 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	2,914	3,016
Seriously Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	14,535	14,997
Total Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	21,938	22,216
Current \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	16,986	15,715
Single-family
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 18,298	20,402
Single-family \| Minimum
Loans in Mortgage Portfolio [Line Items]
Serious delinquency, days past due	90 days
Single-family \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 38,434	36,267
Single-family \| 30 - 59 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	4,489	4,203
Single-family \| 60 - 89 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	2,914	3,016
Single-family \| Seriously Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	14,060	14,384
Single-family \| Total Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	21,463	21,603
Single-family \| Current \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	16,971	14,664
Single-family \| 20- and 30-year or more, amortizing fixed-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	17,635	19,618
Single-family \| 20- and 30-year or more, amortizing fixed-rate \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	37,007	34,849
Single-family \| 20- and 30-year or more, amortizing fixed-rate \| 30 - 59 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	4,323	4,040
Single-family \| 20- and 30-year or more, amortizing fixed-rate \| 60 - 89 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	2,807	2,889
Single-family \| 20- and 30-year or more, amortizing fixed-rate \| Seriously Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	13,581	13,813
Single-family \| 20- and 30-year or more, amortizing fixed-rate \| Total Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	20,711	20,742
Single-family \| 20- and 30-year or more, amortizing fixed-rate \| Current \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	16,296	14,107
Single-family \| 15-year or less, amortizing fixed-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	477	546
Single-family \| 15-year or less, amortizing fixed-rate \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	1,019	963
Single-family \| 15-year or less, amortizing fixed-rate \| 30 - 59 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	112	101
Single-family \| 15-year or less, amortizing fixed-rate \| 60 - 89 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	75	82
Single-family \| 15-year or less, amortizing fixed-rate \| Seriously Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	322	382
Single-family \| 15-year or less, amortizing fixed-rate \| Total Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	509	565
Single-family \| 15-year or less, amortizing fixed-rate \| Current \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	510	398
Single-family \| Adjustable-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	68	76
Single-family \| Adjustable-rate \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	127	124
Single-family \| Adjustable-rate \| 30 - 59 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	13	13
Single-family \| Adjustable-rate \| 60 - 89 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	8	13
Single-family \| Adjustable-rate \| Seriously Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	55	64
Single-family \| Adjustable-rate \| Total Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	76	90
Single-family \| Adjustable-rate \| Current \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	51	34
Single-family \| Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	118	162
Single-family \| Other \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	281	331
Single-family \| Other \| 30 - 59 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	41	49
Single-family \| Other \| 60 - 89 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	24	32
Single-family \| Other \| Seriously Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	102	125
Single-family \| Other \| Total Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	167	206
Single-family \| Other \| Current \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	114	125
Multifamily
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 11	634
Multifamily \| Minimum
Loans in Mortgage Portfolio [Line Items]
Serious delinquency, days past due	60 days
Multifamily \| Maximum
Loans in Mortgage Portfolio [Line Items]
Serious delinquency, days past due	89 days
Multifamily \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 490	1,664
Multifamily \| 30 - 59 Days Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	0	0
Multifamily \| Seriously Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	475	613
Multifamily \| Total Delinquent \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	475	613
Multifamily \| Current \| Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 15	$ 1,051

Mortgage Loans - Loan Restructuring - Aging Analysis (Details) - USD ($)
$ in Millions

3 Months Ended

Mar. 31, 2026

Mar. 31, 2025

Loans in Mortgage Portfolio [Line Items]

Restructured loans, amortized cost

$ 18,309

$ 21,036

Serious delinquency, days past due

90 days

Forbearance and Repayment Plans and Trial Modification

Loans in Mortgage Portfolio [Line Items]