Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Net interest income	$ 5,274	$ 5,435	$ 15,622	$ 15,490
Fee and other income	1,194	175	1,796	552
Net revenues	6,468	5,610	17,418	16,042
Investment gains, net	313	467	689	934
Fair value gains (losses), net	(289)	(491)	(1,020)	(4,971)
Administrative expenses	(664)	(661)	(2,034)	(2,027)
Benefit (provision) for credit losses	(182)	673	1,481	3,458
Foreclosed property income (expense)	(140)	(110)	(391)	(507)
Total credit-related income (expense)	(322)	563	1,090	2,951
TCCA fees	(531)	(465)	(1,552)	(1,358)
Other expenses, net	(427)	(300)	(1,100)	(818)
Income before federal income taxes	4,548	4,723	13,491	10,753
Provision for federal income taxes	(1,525)	(1,527)	(4,495)	(3,475)
Net income	3,023	3,196	8,996	7,278
US Treasury [Member]
Segment Reporting Information [Line Items]
TCCA fees	(531)	(465)	(1,552)	(1,358)
Business Segments [Member] | Single-family [Member]
Segment Reporting Information [Line Items]
Net interest income	4,627	4,857	13,749	13,832
Fee and other income	1,005	77	1,192	222
Net revenues	5,632	4,934	14,941	14,054
Investment gains, net	286	399	557	735
Fair value gains (losses), net	(300)	(499)	(997)	(5,028)
Administrative expenses	(580)	(582)	(1,781)	(1,788)
Benefit (provision) for credit losses	(137)	646	1,518	3,405
Foreclosed property income (expense)	(157)	(114)	(405)	(510)
Total credit-related income (expense)	(294)	532	1,113	2,895
Other expenses, net	(320)	(275)	(731)	(773)
Income before federal income taxes	3,893	4,044	11,550	8,737
Provision for federal income taxes	(1,361)	(1,399)	(4,014)	(3,042)
Net income	2,532	2,645	7,536	5,695
Business Segments [Member] | Single-family [Member] | US Treasury [Member]
Segment Reporting Information [Line Items]
TCCA fees	(531)	(465)	(1,552)	(1,358)
Business Segments [Member] | Multifamily [Member]
Segment Reporting Information [Line Items]
Net interest income	647	578	1,873	1,658
Fee and other income	189	98	604	330
Net revenues	836	676	2,477	1,988
Investment gains, net	27	68	132	199
Fair value gains (losses), net	11	8	(23)	57
Administrative expenses	(84)	(79)	(253)	(239)
Benefit (provision) for credit losses	(45)	27	(37)	53
Foreclosed property income (expense)	17	4	14	3
Total credit-related income (expense)	(28)	31	(23)	56
Other expenses, net	(107)	(25)	(369)	(45)
Income before federal income taxes	655	679	1,941	2,016
Provision for federal income taxes	(164)	(128)	(481)	(433)
Net income	$ 491	$ 551	$ 1,460	$ 1,583