Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 5,377	$ 5,002	$ 10,609	$ 10,348
Fee and other income	239	353	559	602
Net revenues	5,616	5,355	11,168	10,950
Investment gains (losses), net	277	385	527	376
Fair value gains (losses), net	229	(691)	1,274	(731)
Administrative expenses	(755)	(686)	(1,505)	(1,370)
Benefit (provision) for credit losses	1,296	1,267	1,513	1,663
Foreclosed property income (expense)	(139)	(34)	(301)	(251)
Total credit-related income (expense)	1,157	1,233	1,212	1,412
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	(565)	(518)	(1,122)	(1,021)
Other expenses, net	(366)	(291)	(569)	(673)
Income before federal income taxes	5,593	4,787	10,985	8,943
Provision for federal income taxes	(1,136)	(1,587)	(2,267)	(2,970)
Net income	4,457	3,200	8,718	5,973
US Treasury [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	(565)	(518)	(1,122)	(1,021)
Business Segments [Member] | Single-family [Member]
Segment Reporting Information [Line Items]
Net interest income	4,723	4,366	9,284	9,122
Fee and other income	69	111	227	187
Net revenues	4,792	4,477	9,511	9,309
Investment gains (losses), net	252	321	494	271
Fair value gains (losses), net	278	(685)	1,312	(697)
Administrative expenses	(649)	(600)	(1,292)	(1,201)
Benefit (provision) for credit losses	1,295	1,255	1,491	1,655
Foreclosed property income (expense)	(136)	(32)	(298)	(248)
Total credit-related income (expense)	1,159	1,223	1,193	1,407
Other expenses, net	(270)	(155)	(402)	(411)
Income before federal income taxes	4,997	4,063	9,694	7,657
Provision for federal income taxes	(1,044)	(1,401)	(2,060)	(2,653)
Net income	3,953	2,662	7,634	5,004
Business Segments [Member] | Single-family [Member] | US Treasury [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	(565)	(518)	(1,122)	(1,021)
Business Segments [Member] | Multifamily [Member]
Segment Reporting Information [Line Items]
Net interest income	654	636	1,325	1,226
Fee and other income	170	242	332	415
Net revenues	824	878	1,657	1,641
Investment gains (losses), net	25	64	33	105
Fair value gains (losses), net	(49)	(6)	(38)	(34)
Administrative expenses	(106)	(86)	(213)	(169)
Benefit (provision) for credit losses	1	12	22	8
Foreclosed property income (expense)	(3)	(2)	(3)	(3)
Total credit-related income (expense)	(2)	10	19	5
Other expenses, net	(96)	(136)	(167)	(262)
Income before federal income taxes	596	724	1,291	1,286
Provision for federal income taxes	(92)	(186)	(207)	(317)
Net income	$ 504	$ 538	$ 1,084	$ 969