Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Net interest income	$ 5,002	$ 5,286	$ 10,348	$ 10,055
Fee and other income	353	174	602	377
Net revenues	5,355	5,460	10,950	10,432
Investment gains, net	385	398	376	467
Fair value gains (losses), net	(691)	(1,667)	(731)	(4,480)
Administrative expenses	(686)	(678)	(1,370)	(1,366)
Benefit for credit losses	1,267	1,601	1,663	2,785
Foreclosed property expense	(34)	(63)	(251)	(397)
Total credit-related income	1,233	1,538	1,412	2,388
TCCA fees	(518)	(453)	(1,021)	(893)
Other expenses, net	(291)	(254)	(673)	(518)
Income before federal income taxes	4,787	4,344	8,943	6,030
Provision for federal income taxes	(1,587)	(1,398)	(2,970)	(1,948)
Net income	3,200	2,946	5,973	4,082
US Treasury [Member]
Segment Reporting Information [Line Items]
TCCA fees	(518)	(453)	(1,021)	(893)
Business Segments [Member] | Single-family [Member]
Segment Reporting Information [Line Items]
Net interest income	4,366	4,730	9,122	8,975
Fee and other income	111	78	187	145
Net revenues	4,477	4,808	9,309	9,120
Investment gains, net	321	280	271	336
Fair value gains (losses), net	(685)	(1,679)	(697)	(4,529)
Administrative expenses	(600)	(597)	(1,201)	(1,206)
Benefit for credit losses	1,255	1,596	1,655	2,759
Foreclosed property expense	(32)	(61)	(248)	(396)
Total credit-related income	1,223	1,535	1,407	2,363
Other expenses, net	(155)	(252)	(411)	(498)
Income before federal income taxes	4,063	3,642	7,657	4,693
Provision for federal income taxes	(1,401)	(1,254)	(2,653)	(1,643)
Net income	2,662	2,388	5,004	3,050
Business Segments [Member] | Single-family [Member] | US Treasury [Member]
Segment Reporting Information [Line Items]
TCCA fees	(518)	(453)	(1,021)	(893)
Business Segments [Member] | Multifamily [Member]
Segment Reporting Information [Line Items]
Net interest income	636	556	1,226	1,080
Fee and other income	242	96	415	232
Net revenues	878	652	1,641	1,312
Investment gains, net	64	118	105	131
Fair value gains (losses), net	(6)	12	(34)	49
Administrative expenses	(86)	(81)	(169)	(160)
Benefit for credit losses	12	5	8	26
Foreclosed property expense	(2)	(2)	(3)	(1)
Total credit-related income	10	3	5	25
Other expenses, net	(136)	(2)	(262)	(20)
Income before federal income taxes	724	702	1,286	1,337
Provision for federal income taxes	(186)	(144)	(317)	(305)
Net income	$ 538	$ 558	$ 969	$ 1,032