Segment Reporting (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) segments	Jun. 30, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable business segments | segments			2
Net interest income	$ 8,286	$ 5,777	$ 15,028	$ 11,124
Fee and other income	103	90	190	210
Net revenues	8,389	5,867	15,218	11,334
Investment gains (losses), net	646	149	691	(9)
Fair value gains (losses), net	(446)	(1,018)	338	(1,294)
Administrative expenses	(746)	(754)	(1,494)	(1,503)
Benefit (provision) for credit losses	2,588	(12)	3,353	(2,595)
Foreclosed property expense	(41)	(10)	(36)	(90)
Total credit-related income (expense)	2,547	(22)	3,317	(2,685)
TCCA fees	(758)	(660)	(1,489)	(1,297)
Credit enhancement expense	(274)	(360)	(558)	(736)
Change in expected credit enhancement recoveries	(44)	273	(75)	461
Other income (expenses), net	(280)	(261)	(599)	(479)
Income before federal income taxes	9,034	3,214	15,349	3,792
Provision for federal income taxes	(1,882)	(669)	(3,204)	(786)
Net income	7,152	2,545	12,145	3,006
US Treasury
Segment Reporting Information [Line Items]
TCCA fees	(758)	(660)	(1,489)	(1,297)
Business Segments | Single-Family
Segment Reporting Information [Line Items]
Net interest income	7,323	4,939	13,217	9,480
Fee and other income	80	71	142	165
Net revenues	7,403	5,010	13,359	9,645
Investment gains (losses), net	658	96	722	(56)
Fair value gains (losses), net	(386)	(1,030)	354	(1,490)
Administrative expenses	(619)	(625)	(1,242)	(1,254)
Benefit (provision) for credit losses	2,553	219	3,215	(1,953)
Foreclosed property expense	(28)	(3)	(11)	(81)
Total credit-related income (expense)	2,525	216	3,204	(2,034)
Credit enhancement expense	(219)	(307)	(445)	(623)
Change in expected credit enhancement recoveries	(57)	208	(73)	266
Other income (expenses), net	(315)	(252)	(602)	(415)
Income before federal income taxes	8,232	2,656	13,788	2,742
Provision for federal income taxes	(1,725)	(556)	(2,887)	(574)
Net income	6,507	2,100	10,901	2,168
Business Segments | Single-Family | US Treasury
Segment Reporting Information [Line Items]
TCCA fees	(758)	(660)	(1,489)	(1,297)
Business Segments | Multifamily
Segment Reporting Information [Line Items]
Net interest income	963	838	1,811	1,644
Fee and other income	23	19	48	45
Net revenues	986	857	1,859	1,689
Investment gains (losses), net	(12)	53	(31)	47
Fair value gains (losses), net	(60)	12	(16)	196
Administrative expenses	(127)	(129)	(252)	(249)
Benefit (provision) for credit losses	35	(231)	138	(642)
Foreclosed property expense	(13)	(7)	(25)	(9)
Total credit-related income (expense)	22	(238)	113	(651)
Credit enhancement expense	(55)	(53)	(113)	(113)
Change in expected credit enhancement recoveries	13	65	(2)	195
Other income (expenses), net	35	(9)	3	(64)
Income before federal income taxes	802	558	1,561	1,050
Provision for federal income taxes	(157)	(113)	(317)	(212)
Net income	645	445	1,244	838
Business Segments | Multifamily | US Treasury
Segment Reporting Information [Line Items]
TCCA fees	$ 0	$ 0	$ 0	$ 0