Mortgage Loans - Credit Quality Indicators - SF (Details) - Single-family - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	$ 288,639	$ 279,314
One fiscal year before	265,785	489,031
Two fiscal years before	450,253	1,103,809
Three fiscal years before	1,020,997	890,887
Four fiscal years before	820,495	155,447
Prior	812,958	763,925
Total mortgage loans	3,659,127	3,682,413
Total writeoffs	670	866
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	2	2
One fiscal year, writeoff	44	36
Two fiscal years, writeoff	133	54
Three fiscal years, writeoff	116	46
Four fiscal years, writeoff	72	109
Prior	303	619
Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	165,115	157,317
One fiscal year before	169,482	354,060
Two fiscal years before	359,669	1,060,673
Three fiscal years before	1,000,638	887,045
Four fiscal years before	818,130	154,553
Prior	811,170	762,320
Total mortgage loans	3,324,204	3,375,968
Greater than 80% and less than or equal to 90%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	54,914	58,766
One fiscal year before	67,979	97,186
Two fiscal years before	71,956	38,932
Three fiscal years before	18,388	3,432
Four fiscal years before	2,083	806
Prior	1,398	1,167
Total mortgage loans	216,718	200,289
Greater than 90% and less than or equal to 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	68,344	62,216
One fiscal year before	27,646	35,990
Two fiscal years before	16,982	4,014
Three fiscal years before	1,762	363
Four fiscal years before	234	71
Prior	233	230
Total mortgage loans	115,201	102,884
Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	266	1,015
One fiscal year before	678	1,795
Two fiscal years before	1,646	190
Three fiscal years before	209	47
Four fiscal years before	48	17
Prior	157	208
Total mortgage loans	3,004	3,272
20- and 30-year or more, amortizing fixed-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	278,055	268,985
One fiscal year before	256,538	447,259
Two fiscal years before	413,636	932,415
Three fiscal years before	870,282	771,430
Four fiscal years before	716,979	137,546
Prior	711,838	650,407
Total mortgage loans	3,247,328	3,208,042
Total writeoffs	621	803
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	2	2
One fiscal year, writeoff	43	35
Two fiscal years, writeoff	130	53
Three fiscal years, writeoff	114	45
Four fiscal years, writeoff	71	108
Prior	261	560
20- and 30-year or more, amortizing fixed-rate | Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	156,136	148,641
One fiscal year before	161,237	314,384
Two fiscal years before	324,160	889,434
Three fiscal years before	849,984	767,596
Four fiscal years before	714,620	136,654
Prior	710,162	648,964
Total mortgage loans	2,916,299	2,905,673
20- and 30-year or more, amortizing fixed-rate | Greater than 80% and less than or equal to 90%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	53,904	57,686
One fiscal year before	67,163	95,509
Two fiscal years before	71,059	38,790
Three fiscal years before	18,333	3,424
Four fiscal years before	2,078	804
Prior	1,338	1,082
Total mortgage loans	213,875	197,295
20- and 30-year or more, amortizing fixed-rate | Greater than 90% and less than or equal to 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	67,749	61,658
One fiscal year before	27,468	35,602
Two fiscal years before	16,801	4,002
Three fiscal years before	1,757	363
Four fiscal years before	233	71
Prior	205	189
Total mortgage loans	114,213	101,885
20- and 30-year or more, amortizing fixed-rate | Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	266	1,000
One fiscal year before	670	1,764
Two fiscal years before	1,616	189
Three fiscal years before	208	47
Four fiscal years before	48	17
Prior	133	172
Total mortgage loans	2,941	3,189
15-year or less, amortizing fixed-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	8,407	7,951
One fiscal year before	6,793	35,931
Two fiscal years before	31,325	165,347
Three fiscal years before	145,266	117,797
Four fiscal years before	102,032	17,162
Prior	75,904	84,225
Total mortgage loans	369,727	428,413
Total writeoffs	10	8
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	0	0
One fiscal year, writeoff	1	0
Two fiscal years, writeoff	2	1
Three fiscal years, writeoff	2	1
Four fiscal years, writeoff	1	1
Prior	4	5
15-year or less, amortizing fixed-rate | Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	7,508	7,110
One fiscal year before	6,455	35,224
Two fiscal years before	31,140	165,294
Three fiscal years before	145,254	117,795
Four fiscal years before	102,032	17,162
Prior	75,904	84,222
Total mortgage loans	368,293	426,807
15-year or less, amortizing fixed-rate | Greater than 80% and less than or equal to 90%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	576	581
One fiscal year before	314	647
Two fiscal years before	168	52
Three fiscal years before	11	2
Four fiscal years before	0	0
Prior	0	1
Total mortgage loans	1,069	1,283
15-year or less, amortizing fixed-rate | Greater than 90% and less than or equal to 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	323	259
One fiscal year before	24	58
Two fiscal years before	16	1
Three fiscal years before	1	0
Four fiscal years before	0	0
Prior	0	1
Total mortgage loans	364	319
15-year or less, amortizing fixed-rate | Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	1
One fiscal year before	0	2
Two fiscal years before	1	0
Three fiscal years before	0	0
Four fiscal years before	0	0
Prior	0	1
Total mortgage loans	1	4
Adjustable-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	2,177	2,378
One fiscal year before	2,454	5,841
Two fiscal years before	5,292	6,047
Three fiscal years before	5,449	1,660
Four fiscal years before	1,484	712
Prior	8,162	9,720
Total mortgage loans	25,018	26,358
Total writeoffs	2	3
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	0	0
One fiscal year, writeoff	0	1
Two fiscal years, writeoff	1	0
Three fiscal years, writeoff	0	0
Four fiscal years, writeoff	0	0
Prior	1	2
Adjustable-rate | Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	1,471	1,566
One fiscal year before	1,790	4,452
Two fiscal years before	4,369	5,945
Three fiscal years before	5,400	1,654
Four fiscal years before	1,478	710
Prior	8,159	9,716
Total mortgage loans	22,667	24,043
Adjustable-rate | Greater than 80% and less than or equal to 90%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	434	499
One fiscal year before	502	1,030
Two fiscal years before	729	90
Three fiscal years before	44	6
Four fiscal years before	5	2
Prior	2	3
Total mortgage loans	1,716	1,630
Adjustable-rate | Greater than 90% and less than or equal to 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	272	299
One fiscal year before	154	330
Two fiscal years before	165	11
Three fiscal years before	4	0
Four fiscal years before	1	0
Prior	1	1
Total mortgage loans	597	641
Adjustable-rate | Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	14
One fiscal year before	8	29
Two fiscal years before	29	1
Three fiscal years before	1	0
Four fiscal years before	0	0
Prior	0	0
Total mortgage loans	38	44
Other
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	0
One fiscal year before	0	0
Two fiscal years before	0	0
Three fiscal years before	0	0
Four fiscal years before	0	27
Prior	17,054	19,573
Total mortgage loans	17,054	19,600
Total writeoffs	37	52
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	0	0
One fiscal year, writeoff	0	0
Two fiscal years, writeoff	0	0
Three fiscal years, writeoff	0	0
Four fiscal years, writeoff	0	0
Prior	37	52
Other | Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	0
One fiscal year before	0	0
Two fiscal years before	0	0
Three fiscal years before	0	0
Four fiscal years before	0	27
Prior	16,945	19,418
Total mortgage loans	16,945	19,445
Other | Greater than 80% and less than or equal to 90%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	0
One fiscal year before	0	0
Two fiscal years before	0	0
Three fiscal years before	0	0
Four fiscal years before	0	0
Prior	58	81
Total mortgage loans	58	81
Other | Greater than 90% and less than or equal to 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	0
One fiscal year before	0	0
Two fiscal years before	0	0
Three fiscal years before	0	0
Four fiscal years before	0	0
Prior	27	39
Total mortgage loans	27	39
Other | Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	0
One fiscal year before	0	0
Two fiscal years before	0	0
Three fiscal years before	0	0
Four fiscal years before	0	0
Prior	24	35
Total mortgage loans	24	35
Government
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Total mortgage loans	3,600	5,500
Total writeoffs	$ 47	$ 7