Mortgage Loans - Credit Quality Indicators - SF (Details) - Single-family - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2026	Dec. 31, 2025
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	$ 253,600	$ 292,985
One fiscal year before	294,114	270,785
Two fiscal years before	234,505	223,567
Three fiscal years before	192,553	409,856
Four fiscal years before	379,256	940,304
Prior	2,230,660	1,468,991
Total mortgage loans	3,584,688	3,606,488
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	2	5
One fiscal year, writeoff	49	57
Two fiscal years, writeoff	71	94
Three fiscal years, writeoff	76	180
Four fiscal years, writeoff	134	107
Prior	203	280
Total writeoff	535	723
Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	149,324	163,343
One fiscal year before	180,750	160,536
Two fiscal years before	149,391	149,624
Three fiscal years before	138,117	337,271
Four fiscal years before	322,420	922,745
Prior	2,214,204	1,465,398
Total mortgage loans	3,154,206	3,198,917
Greater than 80% and less than or equal to 90%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	42,957	57,484
One fiscal year before	63,892	63,333
Two fiscal years before	56,901	52,872
Three fiscal years before	38,967	53,845
Four fiscal years before	41,725	14,886
Prior	13,373	2,839
Total mortgage loans	257,815	245,259
Greater than 90% and less than or equal to 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	61,246	71,589
One fiscal year before	48,455	44,876
Two fiscal years before	25,770	18,732
Three fiscal years before	12,912	15,552
Four fiscal years before	11,837	2,193
Prior	2,403	539
Total mortgage loans	162,623	153,481
Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	73	569
One fiscal year before	1,017	2,040
Two fiscal years before	2,443	2,339
Three fiscal years before	2,557	3,188
Four fiscal years before	3,274	480
Prior	680	215
Total mortgage loans	10,044	8,831
20- and 30-year or more, amortizing fixed-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	229,566	270,116
One fiscal year before	271,351	261,486
Two fiscal years before	226,796	216,159
Three fiscal years before	186,325	378,287
Four fiscal years before	351,231	809,560
Prior	1,976,629	1,304,902
Total mortgage loans	3,241,898	3,240,510
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	2	5
One fiscal year, writeoff	48	56
Two fiscal years, writeoff	70	92
Three fiscal years, writeoff	75	176
Four fiscal years, writeoff	132	106
Prior	193	242
Total writeoff	520	677
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	129,927	145,040
One fiscal year before	161,662	152,418
Two fiscal years before	142,474	142,942
Three fiscal years before	132,415	306,573
Four fiscal years before	295,080	792,049
Prior	1,960,287	1,301,401
Total mortgage loans	2,821,845	2,840,423
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	40,071	54,527
One fiscal year before	61,243	62,451
Two fiscal years before	56,284	52,313
Three fiscal years before	38,581	53,203
Four fiscal years before	41,221	14,848
Prior	13,301	2,790
Total mortgage loans	250,701	240,132
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	59,495	69,983
One fiscal year before	47,437	44,582
Two fiscal years before	25,610	18,590
Three fiscal years before	12,803	15,374
Four fiscal years before	11,706	2,184
Prior	2,382	517
Total mortgage loans	159,433	151,230
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	73	566
One fiscal year before	1,009	2,035
Two fiscal years before	2,428	2,314
Three fiscal years before	2,526	3,137
Four fiscal years before	3,224	479
Prior	659	194
Total mortgage loans	9,919	8,725
15-year or less, amortizing fixed-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	15,348	15,837
One fiscal year before	15,147	7,324
Two fiscal years before	6,009	5,288
Three fiscal years before	4,364	26,837
Four fiscal years before	23,727	125,843
Prior	229,505	141,455
Total mortgage loans	294,100	322,584
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	0	0
One fiscal year, writeoff	1	1
Two fiscal years, writeoff	1	1
Three fiscal years, writeoff	1	3
Four fiscal years, writeoff	1	1
Prior	3	3
Total writeoff	7	9
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	13,465	13,753
One fiscal year before	13,820	6,794
Two fiscal years before	5,751	5,149
Three fiscal years before	4,306	26,742
Four fiscal years before	23,676	125,837
Prior	229,502	141,455
Total mortgage loans	290,520	319,730
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	1,260	1,464
One fiscal year before	1,113	440
Two fiscal years before	235	127
Three fiscal years before	52	82
Four fiscal years before	46	6
Prior	3	0
Total mortgage loans	2,709	2,119
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	623	619
One fiscal year before	213	88
Two fiscal years before	22	11
Three fiscal years before	5	13
Four fiscal years before	5	0
Prior	0	0
Total mortgage loans	868	731
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	1	2
Two fiscal years before	1	1
Three fiscal years before	1	0
Four fiscal years before	0	0
Prior	0	0
Total mortgage loans	3	4
Adjustable-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	8,686	7,032
One fiscal year before	7,616	1,975
Two fiscal years before	1,700	2,120
Three fiscal years before	1,864	4,732
Four fiscal years before	4,298	4,901
Prior	11,206	7,846
Total mortgage loans	35,370	28,606
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	1
Four fiscal years, writeoff	1	0
Prior	1	0
Total writeoff	2	2
Adjustable-rate | Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	5,932	4,550
One fiscal year before	5,268	1,324
Two fiscal years before	1,166	1,533
Three fiscal years before	1,396	3,956
Four fiscal years before	3,664	4,859
Prior	11,166	7,841
Total mortgage loans	28,592	24,063
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	1,626	1,493
One fiscal year before	1,536	442
Two fiscal years before	382	432
Three fiscal years before	334	560
Four fiscal years before	458	32
Prior	31	4
Total mortgage loans	4,367	2,963
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	1,128	987
One fiscal year before	805	206
Two fiscal years before	138	131
Three fiscal years before	104	165
Four fiscal years before	126	9
Prior	7	1
Total mortgage loans	2,308	1,499
Adjustable-rate | Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	2
One fiscal year before	7	3
Two fiscal years before	14	24
Three fiscal years before	30	51
Four fiscal years before	50	1
Prior	2	0
Total mortgage loans	103	81
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	13,320	14,788
Total mortgage loans	13,320	14,788
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	6	35
Total writeoff	6	35
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	13,249	14,701
Total mortgage loans	13,249	14,701
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	38	45
Total mortgage loans	38	45
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	14	21
Total mortgage loans	14	21
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	19	21
Total mortgage loans	19	21
U.S Government
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Total mortgage loans	$ 2,500	$ 2,800