Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Net interest income	$ 5,229	$ 5,369	$ 15,112	$ 15,978
Fee and other income	402	271	875	830
Net revenues	5,631	5,640	15,987	16,808
Investment gains, net	253	166	847	693
Fair value gains (losses), net	(713)	386	(2,298)	1,660
Administrative expenses	(749)	(740)	(2,237)	(2,245)
Benefit (provision) for credit losses	1,857	716	3,732	2,229
Foreclosed property income (expense)	(96)	(159)	(364)	(460)
Total credit-related income (expense)	(1,761)	(557)	(3,368)	(1,769)
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	(613)	(576)	(1,806)	(1,698)
Other expenses, net	(571)	(377)	(1,514)	(946)
Income before federal income taxes	4,999	5,056	12,347	16,041
Provision for federal income taxes	(1,036)	(1,045)	(2,552)	(3,312)
Net income	3,963	4,011	9,795	12,729
US Treasury [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	(613)	(576)	(1,806)	(1,698)
Business Segments [Member] | Single-family [Member]
Segment Reporting Information [Line Items]
Net interest income	4,484	4,670	12,942	13,954
Fee and other income	156	79	350	306
Net revenues	4,640	4,749	13,292	14,260
Investment gains, net	198	146	709	640
Fair value gains (losses), net	(719)	417	(2,364)	1,729
Administrative expenses	(634)	(636)	(1,899)	(1,928)
Benefit (provision) for credit losses	(1,840)	(732)	(3,753)	(2,223)
Foreclosed property income (expense)	(93)	(150)	(362)	(448)
Total credit-related income (expense)	(1,747)	(582)	(3,391)	(1,775)
Other expenses, net	(424)	(282)	(1,179)	(684)
Income before federal income taxes	4,195	4,400	10,144	14,094
Provision for federal income taxes	(872)	(938)	(2,125)	(2,998)
Net income	3,323	3,462	8,019	11,096
Business Segments [Member] | Single-family [Member] | US Treasury [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	(613)	(576)	(1,806)	(1,698)
Business Segments [Member] | Multifamily [Member]
Segment Reporting Information [Line Items]
Net interest income	745	699	2,170	2,024
Fee and other income	246	192	525	524
Net revenues	991	891	2,695	2,548
Investment gains, net	55	20	138	53
Fair value gains (losses), net	6	(31)	66	(69)
Administrative expenses	(115)	(104)	(338)	(317)
Benefit (provision) for credit losses	(17)	(16)	(21)	(6)
Foreclosed property income (expense)	(3)	(9)	(2)	(12)
Total credit-related income (expense)	(14)	(25)	(23)	(6)
Other expenses, net	(147)	(95)	(335)	(262)
Income before federal income taxes	804	656	2,203	1,947
Provision for federal income taxes	(164)	(107)	(427)	(314)
Net income	640	549	1,776	1,633
Business Segments [Member] | Multifamily [Member] | US Treasury [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Tax Cut Continuation Act of 2011 (“TCCA”) fees	$ 0	$ 0	$ 0	$ 0