Mortgage Loans - Credit Quality Indicators - SF (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans held for investment	$ 3,968,737	$ 3,659,247
Single-family
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,200,915	1,253,449
One fiscal year before	1,082,870	367,647
Two fiscal years before	207,663	178,798
Three fiscal years before	100,239	226,092
Four fiscal years before	135,670	272,831
Prior	829,967	972,993
Total loans held for investment	3,557,324	3,271,810
Single-family | Less than or equal to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,001,159	978,509
One fiscal year before	1,040,601	277,248
Two fiscal years before	204,398	154,357
Three fiscal years before	98,924	220,388
Four fiscal years before	134,953	270,966
Prior	826,785	960,696
Total loans held for investment	3,306,820	2,862,164
Single-family | Greater than 80% and less than or equal to 90%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	132,354	163,839
One fiscal year before	39,973	86,192
Two fiscal years before	2,712	23,574
Three fiscal years before	1,067	5,346
Four fiscal years before	632	1,635
Prior	1,972	7,288
Total loans held for investment	178,710	287,874
Single-family | Greater than 90% and less than or equal to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	67,381	111,073
One fiscal year before	2,284	4,200
Two fiscal years before	544	832
Three fiscal years before	231	270
Four fiscal years before	60	137
Prior	597	2,608
Total loans held for investment	71,097	119,120
Single-family | Greater than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	21	28
One fiscal year before	12	7
Two fiscal years before	9	35
Three fiscal years before	17	88
Four fiscal years before	25	93
Prior	613	2,401
Total loans held for investment	697	2,652
Single-family | 20- and 30-year or more, amortizing fixed-rate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	994,858	1,061,427
One fiscal year before	923,269	323,414
Two fiscal years before	181,151	160,137
Three fiscal years before	89,126	188,912
Four fiscal years before	111,760	222,969
Prior	668,941	785,344
Total loans held for investment	2,969,105	2,742,203
Single-family | 20- and 30-year or more, amortizing fixed-rate | Less than or equal to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	798,830	794,156
One fiscal year before	881,290	233,994
Two fiscal years before	177,909	135,849
Three fiscal years before	87,825	183,315
Four fiscal years before	111,059	221,172
Prior	666,327	775,636
Total loans held for investment	2,723,240	2,344,122
Single-family | 20- and 30-year or more, amortizing fixed-rate | Greater than 80% and less than or equal to 90%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	129,340	157,500
One fiscal year before	39,689	85,227
Two fiscal years before	2,689	23,440
Three fiscal years before	1,056	5,270
Four fiscal years before	622	1,592
Prior	1,687	5,958
Total loans held for investment	175,083	278,987
Single-family | 20- and 30-year or more, amortizing fixed-rate | Greater than 90% and less than or equal to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	66,667	109,743
One fiscal year before	2,278	4,186
Two fiscal years before	544	820
Three fiscal years before	229	250
Four fiscal years before	57	124
Prior	460	1,994
Total loans held for investment	70,235	117,117
Single-family | 20- and 30-year or more, amortizing fixed-rate | Greater than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	21	28
One fiscal year before	12	7
Two fiscal years before	9	28
Three fiscal years before	16	77
Four fiscal years before	22	81
Prior	467	1,756
Total loans held for investment	547	1,977
Single-family | 15-year or less, amortizing fixed-rate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	199,318	188,797
One fiscal year before	157,340	42,194
Two fiscal years before	25,406	15,809
Three fiscal years before	9,600	31,518
Four fiscal years before	20,720	46,102
Prior	121,043	132,639
Total loans held for investment	533,427	457,059
Single-family | 15-year or less, amortizing fixed-rate | Less than or equal to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	196,163	181,418
One fiscal year before	157,076	41,374
Two fiscal years before	25,390	15,768
Three fiscal years before	9,595	31,497
Four fiscal years before	20,715	46,088
Prior	121,027	132,596
Total loans held for investment	529,966	448,741
Single-family | 15-year or less, amortizing fixed-rate | Greater than 80% and less than or equal to 90%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,576	6,105
One fiscal year before	259	811
Two fiscal years before	16	35
Three fiscal years before	4	14
Four fiscal years before	2	8
Prior	7	20
Total loans held for investment	2,864	6,993
Single-family | 15-year or less, amortizing fixed-rate | Greater than 90% and less than or equal to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	579	1,274
One fiscal year before	5	9
Two fiscal years before	0	3
Three fiscal years before	1	4
Four fiscal years before	1	3
Prior	4	10
Total loans held for investment	590	1,303
Single-family | 15-year or less, amortizing fixed-rate | Greater than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One fiscal year before	0	0
Two fiscal years before	0	3
Three fiscal years before	0	3
Four fiscal years before	2	3
Prior	5	13
Total loans held for investment	7	22
Single-family | Adjustable-rate
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	6,739	3,225
One fiscal year before	2,261	1,994
Two fiscal years before	1,072	2,492
Three fiscal years before	1,240	4,784
Four fiscal years before	2,526	2,683
Prior	12,504	16,263
Total loans held for investment	26,342	31,441
Single-family | Adjustable-rate | Less than or equal to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	6,166	2,935
One fiscal year before	2,235	1,839
Two fiscal years before	1,065	2,412
Three fiscal years before	1,236	4,765
Four fiscal years before	2,524	2,678
Prior	12,501	16,248
Total loans held for investment	25,727	30,877
Single-family | Adjustable-rate | Greater than 80% and less than or equal to 90%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	438	234
One fiscal year before	25	152
Two fiscal years before	7	79
Three fiscal years before	4	19
Four fiscal years before	2	5
Prior	3	12
Total loans held for investment	479	501
Single-family | Adjustable-rate | Greater than 90% and less than or equal to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	135	56
One fiscal year before	1	3
Two fiscal years before	0	1
Three fiscal years before	0	0
Four fiscal years before	0	0
Prior	0	2
Total loans held for investment	136	62
Single-family | Adjustable-rate | Greater than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
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	0	1
Total loans held for investment	0	1
Single-family | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One fiscal year before	0	45
Two fiscal years before	34	360
Three fiscal years before	273	878
Four fiscal years before	664	1,077
Prior	27,479	38,747
Total loans held for investment	28,450	41,107
Single-family | Other | Less than or equal to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One fiscal year before	0	41
Two fiscal years before	34	328
Three fiscal years before	268	811
Four fiscal years before	655	1,028
Prior	26,930	36,216
Total loans held for investment	27,887	38,424
Single-family | Other | Greater than 80% and less than or equal to 90%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One fiscal year before	0	2
Two fiscal years before	0	20
Three fiscal years before	3	43
Four fiscal years before	6	30
Prior	275	1,298
Total loans held for investment	284	1,393
Single-family | Other | Greater than 90% and less than or equal to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One fiscal year before	0	2
Two fiscal years before	0	8
Three fiscal years before	1	16
Four fiscal years before	2	10
Prior	133	602
Total loans held for investment	136	638
Single-family | Other | Greater than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One fiscal year before	0	0
Two fiscal years before	0	4
Three fiscal years before	1	8
Four fiscal years before	1	9
Prior	141	631
Total loans held for investment	143	652
Single-family | Government
Financing Receivable, Credit Quality Indicator [Line Items]
Total recorded investment	$ 9,500	$ 13,500