Mortgage Loans - Loan Restructuring - Subsequent Default (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	$ 2,442	$ 2,299	$ 4,722	$ 4,146
Payment Delay as a Result of a Payment Deferral (Only)
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	1,328	1,499	2,728	2,705
Payment Delay and Term Extension
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	1,030	783	1,878	1,398
Payment Delay, Term Extension, Interest Rate Reduction, and Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	84	17	116	43
Single-family
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	2,421	2,299	4,701	4,142
Single-family | Payment Delay as a Result of a Payment Deferral (Only)
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	1,328	1,499	2,728	2,705
Single-family | Payment Delay and Term Extension
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	1,030	783	1,878	1,398
Single-family | Payment Delay, Term Extension, Interest Rate Reduction, and Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	63	17	95	39
Single-family | 20- and 30-year or more, amortizing fixed-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	2,358	2,223	4,579	4,000
Single-family | 20- and 30-year or more, amortizing fixed-rate | Payment Delay as a Result of a Payment Deferral (Only)
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	1,280	1,438	2,631	2,592
Single-family | 20- and 30-year or more, amortizing fixed-rate | Payment Delay and Term Extension
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	1,021	774	1,863	1,383
Single-family | 20- and 30-year or more, amortizing fixed-rate | Payment Delay, Term Extension, Interest Rate Reduction, and Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	57	11	85	25
Single-family | 15-year or less, amortizing fixed-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	35	40	68	73
Single-family | 15-year or less, amortizing fixed-rate | Payment Delay as a Result of a Payment Deferral (Only)
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	32	40	65	73
Single-family | 15-year or less, amortizing fixed-rate | Payment Delay and Term Extension
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	3	0	3	0
Single-family | 15-year or less, amortizing fixed-rate | Payment Delay, Term Extension, Interest Rate Reduction, and Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	0	0	0	0
Single-family | Adjustable-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	3	4	9	9
Single-family | Adjustable-rate | Payment Delay as a Result of a Payment Deferral (Only)
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	2	4	6	7
Single-family | Adjustable-rate | Payment Delay and Term Extension
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	0	0	0	0
Single-family | Adjustable-rate | Payment Delay, Term Extension, Interest Rate Reduction, and Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	1	0	3	2
Single-family | Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	25	32	45	60
Single-family | Other | Payment Delay as a Result of a Payment Deferral (Only)
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	14	17	26	33
Single-family | Other | Payment Delay and Term Extension
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	6	9	12	15
Single-family | Other | Payment Delay, Term Extension, Interest Rate Reduction, and Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	5	6	7	12
Multifamily
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	21	0	21	4
Multifamily | Payment Delay as a Result of a Payment Deferral (Only)
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	0	0	0	0
Multifamily | Payment Delay and Term Extension
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	0	0	0	0
Multifamily | Payment Delay, Term Extension, Interest Rate Reduction, and Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost, subsequent default	$ 21	$ 0	$ 21	$ 4