Segment Reporting (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segments	Sep. 30, 2020 USD ($)
Segment Reporting Information [Line Items]
Number of reportable business segments | segments			2
Net interest income	$ 6,972	$ 6,656	$ 22,000	$ 17,780
Fee and other income	111	93	301	303
Net revenues	7,083	6,749	22,301	18,083
Investment gains (losses), net	243	653	934	644
Fair value gains (losses), net	(17)	(327)	321	(1,621)
Administrative expenses	(745)	(762)	(2,239)	(2,265)
Benefit (provision) for credit losses	937	501	4,290	(2,094)
Foreclosed property income (expense)	(69)	(71)	(105)	(161)
Total credit-related income (expense)	868	430	4,185	(2,255)
TCCA fees	(781)	(679)	(2,270)	(1,976)
Credit enhancement expense	(233)	(325)	(791)	(1,061)
Change in expected credit enhancement recoveries	(42)	(48)	(117)	413
Other expenses, net	(268)	(313)	(867)	(792)
Income before federal income taxes	6,108	5,378	21,457	9,170
Provision for federal income taxes	(1,266)	(1,149)	(4,470)	(1,935)
Net income	4,842	4,229	16,987	7,235
US Treasury
Segment Reporting Information [Line Items]
TCCA fees	(781)	(679)	(2,270)	(1,976)
Business segments | Single-Family
Segment Reporting Information [Line Items]
Net interest income	5,870	5,870	19,087	15,350
Fee and other income	86	73	228	238
Net revenues	5,956	5,943	19,315	15,588
Investment gains (losses), net	222	583	944	527
Fair value gains (losses), net	(31)	(244)	323	(1,734)
Administrative expenses	(620)	(634)	(1,862)	(1,888)
Benefit (provision) for credit losses	887	542	4,102	(1,411)
Foreclosed property income (expense)	(80)	(64)	(91)	(145)
Total credit-related income (expense)	807	478	4,011	(1,556)
Credit enhancement expense	(174)	(274)	(619)	(897)
Change in expected credit enhancement recoveries	(28)	(48)	(101)	218
Other expenses, net	(261)	(307)	(863)	(722)
Income before federal income taxes	5,090	4,818	18,878	7,560
Provision for federal income taxes	(1,065)	(1,049)	(3,952)	(1,623)
Net income	4,025	3,769	14,926	5,937
Business segments | Single-Family | US Treasury
Segment Reporting Information [Line Items]
TCCA fees	(781)	(679)	(2,270)	(1,976)
Business segments | Multifamily
Segment Reporting Information [Line Items]
Net interest income	1,102	786	2,913	2,430
Fee and other income	25	20	73	65
Net revenues	1,127	806	2,986	2,495
Investment gains (losses), net	21	70	(10)	117
Fair value gains (losses), net	14	(83)	(2)	113
Administrative expenses	(125)	(128)	(377)	(377)
Benefit (provision) for credit losses	50	(41)	188	(683)
Foreclosed property income (expense)	11	(7)	(14)	(16)
Total credit-related income (expense)	61	(48)	174	(699)
Credit enhancement expense	(59)	(51)	(172)	(164)
Change in expected credit enhancement recoveries	(14)	0	(16)	195
Other expenses, net	(7)	(6)	(4)	(70)
Income before federal income taxes	1,018	560	2,579	1,610
Provision for federal income taxes	(201)	(100)	(518)	(312)
Net income	817	460	2,061	1,298
Business segments | Multifamily | US Treasury
Segment Reporting Information [Line Items]
TCCA fees	$ 0	$ 0	$ 0	$ 0