Mortgage Loans - Credit Quality Indicators - SF (Details) - Single-family - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	$ 39,447	$ 279,314
One fiscal year before	295,469	489,031
Two fiscal years before	480,938	1,103,809
Three fiscal years before	1,085,273	890,887
Four fiscal years before	875,301	155,447
Prior	894,017	763,925
Total mortgage loans	3,670,445	3,682,413
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	0	2
One fiscal year, writeoff	5	36
Two fiscal years, writeoff	16	54
Three fiscal years, writeoff	12	46
Four fiscal years, writeoff	6	109
Prior	41	619
Total writeoff	80	866
Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	23,458	157,317
One fiscal year before	170,072	354,060
Two fiscal years before	356,221	1,060,673
Three fiscal years before	1,048,207	887,045
Four fiscal years before	871,713	154,553
Prior	891,620	762,320
Total mortgage loans	3,361,291	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	6,189	58,766
One fiscal year before	65,899	97,186
Two fiscal years before	90,964	38,932
Three fiscal years before	33,597	3,432
Four fiscal years before	3,139	806
Prior	1,885	1,167
Total mortgage loans	201,673	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	9,800	62,216
One fiscal year before	58,353	35,990
Two fiscal years before	31,993	4,014
Three fiscal years before	3,257	363
Four fiscal years before	392	71
Prior	300	230
Total mortgage loans	104,095	102,884
Greater than 100%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	0	1,015
One fiscal year before	1,145	1,795
Two fiscal years before	1,760	190
Three fiscal years before	212	47
Four fiscal years before	57	17
Prior	212	208
Total mortgage loans	3,386	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	38,232	268,985
One fiscal year before	284,737	447,259
Two fiscal years before	440,353	932,415
Three fiscal years before	918,764	771,430
Four fiscal years before	759,626	137,546
Prior	770,314	650,407
Total mortgage loans	3,212,026	3,208,042
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current fiscal year, writeoff	0	2
One fiscal year, writeoff	5	35
Two fiscal years, writeoff	15	53
Three fiscal years, writeoff	12	45
Four fiscal years, writeoff	6	108
Prior	35	560
Total writeoff	73	803
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	22,414	148,641
One fiscal year before	160,958	314,384
Two fiscal years before	317,454	889,434
Three fiscal years before	881,833	767,596
Four fiscal years before	756,047	136,654
Prior	768,064	648,964
Total mortgage loans	2,906,770	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	6,088	57,686
One fiscal year before	64,778	95,509
Two fiscal years before	89,524	38,790
Three fiscal years before	33,474	3,424
Four fiscal years before	3,131	804
Prior	1,807	1,082
Total mortgage loans	198,802	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	9,730	61,658
One fiscal year before	57,866	35,602
Two fiscal years before	31,637	4,002
Three fiscal years before	3,245	363
Four fiscal years before	391	71
Prior	264	189
Total mortgage loans	103,133	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	0	1,000
One fiscal year before	1,135	1,764
Two fiscal years before	1,738	189
Three fiscal years before	212	47
Four fiscal years before	57	17
Prior	179	172
Total mortgage loans	3,321	3,189
15-year or less, amortizing fixed-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	981	7,951
One fiscal year before	8,058	35,931
Two fiscal years before	34,852	165,347
Three fiscal years before	160,581	117,797
Four fiscal years before	114,053	17,162
Prior	94,808	84,225
Total mortgage loans	413,333	428,413
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	1	1
Three fiscal years, writeoff	0	1
Four fiscal years, writeoff	0	1
Prior	1	5
Total writeoff	2	8
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	879	7,110
One fiscal year before	7,300	35,224
Two fiscal years before	34,299	165,294
Three fiscal years before	160,540	117,795
Four fiscal years before	114,051	17,162
Prior	94,806	84,222
Total mortgage loans	411,875	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	61	581
One fiscal year before	554	647
Two fiscal years before	508	52
Three fiscal years before	39	2
Four fiscal years before	2	0
Prior	1	1
Total mortgage loans	1,165	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	41	259
One fiscal year before	203	58
Two fiscal years before	44	1
Three fiscal years before	2	0
Four fiscal years before	0	0
Prior	0	1
Total mortgage loans	290	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	1	2
Two fiscal years before	1	0
Three fiscal years before	0	0
Four fiscal years before	0	0
Prior	1	1
Total mortgage loans	3	4
Adjustable-rate
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	234	2,378
One fiscal year before	2,674	5,841
Two fiscal years before	5,733	6,047
Three fiscal years before	5,928	1,660
Four fiscal years before	1,622	712
Prior	9,895	9,720
Total mortgage loans	26,086	26,358
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	0
Three fiscal years, writeoff	0	0
Four fiscal years, writeoff	0	0
Prior	0	2
Total writeoff	0	3
Adjustable-rate | Less than or equal to 80%
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Current fiscal year	165	1,566
One fiscal year before	1,814	4,452
Two fiscal years before	4,468	5,945
Three fiscal years before	5,834	1,654
Four fiscal years before	1,615	710
Prior	9,889	9,716
Total mortgage loans	23,785	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	40	499
One fiscal year before	567	1,030
Two fiscal years before	932	90
Three fiscal years before	84	6
Four fiscal years before	6	2
Prior	5	3
Total mortgage loans	1,634	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	29	299
One fiscal year before	284	330
Two fiscal years before	312	11
Three fiscal years before	10	0
Four fiscal years before	1	0
Prior	0	1
Total mortgage loans	636	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	9	29
Two fiscal years before	21	1
Three fiscal years before	0	0
Four fiscal years before	0	0
Prior	1	0
Total mortgage loans	31	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	19,000	19,573
Total mortgage loans	19,000	19,600
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	5	52
Total writeoff	5	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	18,861	19,418
Total mortgage loans	18,861	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	72	81
Total mortgage loans	72	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	36	39
Total mortgage loans	36	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	31	35
Total mortgage loans	31	35
U.S Government
Financing Receivable, before Allowance for Credit Loss, by Origination Year [Abstract]
Total mortgage loans	4,800	5,500
Financing Receivable, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total writeoff	$ 35	$ 7