Mortgage Loans - Credit Quality Indicators - SF (Details) - Single-family - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	$ 37,854	$ 288,639
One fiscal year before	307,139	265,785
Two fiscal years before	258,317	450,253
Three fiscal years before	441,509	1,020,997
Four fiscal years before	1,002,971	820,495
Prior	1,594,727	812,958
Total mortgage loans	3,642,517	3,659,127
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	0	2
One fiscal year, writeoff	8	44
Two fiscal years, writeoff	18	133
Three fiscal years, writeoff	40	116
Four fiscal years, writeoff	24	72
Prior	97	303
Total writeoff	187	670
Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	23,674	165,115
One fiscal year before	184,339	169,482
Two fiscal years before	171,176	359,669
Three fiscal years before	362,958	1,000,638
Four fiscal years before	986,309	818,130
Prior	1,590,860	811,170
Total mortgage loans	3,319,316	3,324,204
Greater than 80% and less than or equal to 90%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	5,761	54,914
One fiscal year before	61,135	67,979
Two fiscal years before	65,724	71,956
Three fiscal years before	62,849	18,388
Four fiscal years before	14,731	2,083
Prior	3,236	1,398
Total mortgage loans	213,436	216,718
Greater than 90% and less than or equal to 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	8,419	68,344
One fiscal year before	61,262	27,646
Two fiscal years before	20,600	16,982
Three fiscal years before	13,920	1,762
Four fiscal years before	1,688	234
Prior	430	233
Total mortgage loans	106,319	115,201
Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	266
One fiscal year before	403	678
Two fiscal years before	817	1,646
Three fiscal years before	1,782	209
Four fiscal years before	243	48
Prior	201	157
Total mortgage loans	3,446	3,004
20- and 30-year or more, amortizing fixed-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	35,614	278,055
One fiscal year before	295,890	256,538
Two fiscal years before	249,501	413,636
Three fiscal years before	406,102	870,282
Four fiscal years before	857,050	716,979
Prior	1,400,486	711,838
Total mortgage loans	3,244,643	3,247,328
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	0	2
One fiscal year, writeoff	8	43
Two fiscal years, writeoff	18	130
Three fiscal years, writeoff	39	114
Four fiscal years, writeoff	24	71
Prior	74	261
Total writeoff	163	621
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	21,744	156,136
One fiscal year before	174,572	161,237
Two fiscal years before	163,228	324,160
Three fiscal years before	328,482	849,984
Four fiscal years before	840,437	714,620
Prior	1,396,722	710,162
Total mortgage loans	2,925,185	2,916,299
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	5,580	53,904
One fiscal year before	60,119	67,163
Two fiscal years before	65,003	71,059
Three fiscal years before	62,117	18,333
Four fiscal years before	14,690	2,078
Prior	3,180	1,338
Total mortgage loans	210,689	213,875
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	8,290	67,749
One fiscal year before	60,797	27,468
Two fiscal years before	20,461	16,801
Three fiscal years before	13,756	1,757
Four fiscal years before	1,682	233
Prior	404	205
Total mortgage loans	105,390	114,213
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	0	266
One fiscal year before	402	670
Two fiscal years before	809	1,616
Three fiscal years before	1,747	208
Four fiscal years before	241	48
Prior	180	133
Total mortgage loans	3,379	2,941
15-year or less, amortizing fixed-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	1,801	8,407
One fiscal year before	8,982	6,793
Two fiscal years before	6,426	31,325
Three fiscal years before	30,239	145,266
Four fiscal years before	140,591	102,032
Prior	168,651	75,904
Total mortgage loans	356,690	369,727
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	0	2
Three fiscal years, writeoff	1	2
Four fiscal years, writeoff	0	1
Prior	1	4
Total writeoff	2	10
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	1,599	7,508
One fiscal year before	8,146	6,455
Two fiscal years before	6,163	31,140
Three fiscal years before	30,106	145,254
Four fiscal years before	140,583	102,032
Prior	168,651	75,904
Total mortgage loans	355,248	368,293
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	119	576
One fiscal year before	585	314
Two fiscal years before	250	168
Three fiscal years before	117	11
Four fiscal years before	8	0
Prior	0	0
Total mortgage loans	1,079	1,069
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	83	323
One fiscal year before	251	24
Two fiscal years before	13	16
Three fiscal years before	15	1
Four fiscal years before	0	0
Prior	0	0
Total mortgage loans	362	364
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	0
One fiscal year before	0	0
Two fiscal years before	0	1
Three fiscal years before	1	0
Four fiscal years before	0	0
Prior	0	0
Total mortgage loans	1	1
Adjustable-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	439	2,177
One fiscal year before	2,267	2,454
Two fiscal years before	2,390	5,292
Three fiscal years before	5,168	5,449
Four fiscal years before	5,330	1,484
Prior	9,172	8,162
Total mortgage loans	24,766	25,018
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	1
Three fiscal years, writeoff	0	0
Four fiscal years, writeoff	0	0
Prior	0	1
Total writeoff	0	2
Adjustable-rate | Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	331	1,471
One fiscal year before	1,621	1,790
Two fiscal years before	1,785	4,369
Three fiscal years before	4,370	5,400
Four fiscal years before	5,289	1,478
Prior	9,165	8,159
Total mortgage loans	22,561	22,667
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	62	434
One fiscal year before	431	502
Two fiscal years before	471	729
Three fiscal years before	615	44
Four fiscal years before	33	5
Prior	6	2
Total mortgage loans	1,618	1,716
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	46	272
One fiscal year before	214	154
Two fiscal years before	126	165
Three fiscal years before	149	4
Four fiscal years before	6	1
Prior	1	1
Total mortgage loans	542	597
Adjustable-rate | Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	0
One fiscal year before	1	8
Two fiscal years before	8	29
Three fiscal years before	34	1
Four fiscal years before	2	0
Prior	0	0
Total mortgage loans	45	38
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	0
Prior	16,418	17,054
Total mortgage loans	16,418	17,054
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	22	37
Total writeoff	22	37
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	0
Prior	16,322	16,945
Total mortgage loans	16,322	16,945
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	50	58
Total mortgage loans	50	58
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	25	27
Total mortgage loans	25	27
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	21	24
Total mortgage loans	21	24
U.S Government
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Total mortgage loans	3,300	3,600
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total writeoff	$ 2	$ 47