Mortgage Loans - Loan Restructuring - Aging Analysis (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 15,972	$ 16,693	$ 32,993	$ 34,274
Serious delinquency, days past due			90 days
Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			$ 33,992	36,422
30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			4,431	3,945
60 - 89 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			3,006	2,455
Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			12,250	13,152
Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			19,687	19,552
Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			14,305	16,870
Single-family
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	15,584	15,772	$ 32,599	32,644
Single-family | Minimum
Loans in Mortgage Portfolio [Line Items]
Serious delinquency, days past due			90 days		90 days
Single-family | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			$ 32,846	34,771
Single-family | 30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			4,431	3,926
Single-family | 60 - 89 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			3,006	2,455
Single-family | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			11,927	12,107
Single-family | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			19,364	18,488
Single-family | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			13,482	16,283
Single-family | 20- and 30-year or more, amortizing fixed-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	14,934	14,978	31,249	30,942
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			31,406	32,877
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			4,240	3,722
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			2,874	2,332
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			11,401	11,455
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			18,515	17,509
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			12,891	15,368
Single-family | 15-year or less, amortizing fixed-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	457	538	876	1,051
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			939	1,160
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			118	115
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			93	78
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			349	405
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			560	598
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			379	562
Single-family | Adjustable-rate
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	57	62	112	119
Single-family | Adjustable-rate | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			116	133
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	14
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			7	8
Single-family | Adjustable-rate | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			50	55
Single-family | Adjustable-rate | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			70	77
Single-family | Adjustable-rate | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			46	56
Single-family | Other
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	136	194	362	532
Single-family | Other | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			385	601
Single-family | Other | 30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			60	75
Single-family | Other | 60 - 89 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			32	37
Single-family | Other | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			127	192
Single-family | Other | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			219	304
Single-family | Other | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			166	297
Multifamily
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost	$ 388	$ 921	$ 394	1,630
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			$ 1,146	1,651
Multifamily | 30 - 59 Days Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			0	19
Multifamily | Seriously Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			323	1,045
Multifamily | Total Delinquent | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			323	1,064
Multifamily | Current | Forbearance and Repayment Plans and Trial Modification
Loans in Mortgage Portfolio [Line Items]
Restructured loans, amortized cost			$ 823	$ 587