Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 5,369	$ 5,274	$ 15,978	$ 15,622
Fee and other income	271	1,194	830	1,796
Net revenues	5,640	6,468	16,808	17,418
Investment gains (losses), net	166	313	693	689
Fair value gains (losses), net	386	(289)	1,660	(1,020)
Administrative expenses	(740)	(664)	(2,245)	(2,034)
Benefit (provision) for credit losses	716	(182)	2,229	1,481
Foreclosed property income (expense)	(159)	(140)	(460)	(391)
Total credit-related income (expense)	557	(322)	1,769	1,090
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	(576)	(531)	(1,698)	(1,552)
Other expenses, net	(377)	(427)	(946)	(1,100)
Income before federal income taxes	5,056	4,548	16,041	13,491
Provision for federal income taxes	(1,045)	(1,525)	(3,312)	(4,495)
Net income	4,011	3,023	12,729	8,996
US Treasury [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	(576)	(531)	(1,698)	(1,552)
Business Segments [Member] | Single-family [Member]
Segment Reporting Information [Line Items]
Net interest income	4,670	4,627	13,954	13,749
Fee and other income	79	1,005	306	1,192
Net revenues	4,749	5,632	14,260	14,941
Investment gains (losses), net	146	286	640	557
Fair value gains (losses), net	417	(300)	1,729	(997)
Administrative expenses	(636)	(580)	(1,928)	(1,781)
Benefit (provision) for credit losses	732	(137)	2,223	1,518
Foreclosed property income (expense)	(150)	(157)	(448)	(405)
Total credit-related income (expense)	582	(294)	1,775	1,113
Other expenses, net	(282)	(320)	(684)	(731)
Income before federal income taxes	4,400	3,893	14,094	11,550
Provision for federal income taxes	(938)	(1,361)	(2,998)	(4,014)
Net income	3,462	2,532	11,096	7,536
Business Segments [Member] | Single-family [Member] | US Treasury [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	(576)	(531)	(1,698)	(1,552)
Business Segments [Member] | Multifamily [Member]
Segment Reporting Information [Line Items]
Net interest income	699	647	2,024	1,873
Fee and other income	192	189	524	604
Net revenues	891	836	2,548	2,477
Investment gains (losses), net	20	27	53	132
Fair value gains (losses), net	(31)	11	(69)	(23)
Administrative expenses	(104)	(84)	(317)	(253)
Benefit (provision) for credit losses	(16)	(45)	6	(37)
Foreclosed property income (expense)	(9)	17	(12)	14
Total credit-related income (expense)	(25)	(28)	(6)	(23)
Other expenses, net	(95)	(107)	(262)	(369)
Income before federal income taxes	656	655	1,947	1,941
Provision for federal income taxes	(107)	(164)	(314)	(481)
Net income	$ 549	$ 491	$ 1,633	$ 1,460