Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net interest income	$ 5,850	$ 5,229	$ 5,150	$ 4,733	$ 4,973	$ 5,369	$ 5,377	$ 5,232	$ 20,962	$ 20,951	$ 20,733
Fee and other income									1,176	979	2,227
Net revenues									22,138	21,930	22,960
Investment gains, net	923	253	461	133	259	166	277	250	1,770	952	1,522
Fair value losses, net	84	(713)	(754)	(831)	(539)	386	229	1,045	(2,214)	1,121	(1,211)
Administrative expenses	(786)	(749)	(744)	(744)	(814)	(740)	(755)	(750)	(3,023)	(3,059)	(2,737)
Benefit for credit losses	279	1,857	1,225	650	1,080	716	1,296	217	4,011	3,309	2,041
Foreclosed property income (expense)	(151)	(96)	(128)	(140)	(157)	(159)	(139)	(162)	(515)	(617)	(521)
Credit-related income (expense)									3,496	2,692	1,520
Temporary Payroll Cut Continuation Act of 2011 (TCCA) fees	(626)	(613)	(600)	(593)	(586)	(576)	(565)	(557)	(2,432)	(2,284)	(2,096)
Other expenses, net	(644)	(571)	(535)	(408)	(307)	(377)	(366)	(203)	(2,158)	(1,253)	(1,511)
Income before federal income taxes	5,230	4,999	4,321	3,027	4,058	5,056	5,593	5,392	17,577	20,099	18,447
Provision for federal income taxes	(865)	(1,036)	(889)	(627)	(828)	(1,045)	(1,136)	(1,131)	(3,417)	(4,140)	(15,984)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 4,365	$ 3,963	$ 3,432	$ 2,400	$ 3,230	$ 4,011	$ 4,457	$ 4,261	14,160	15,959	2,463
US Treasury [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Cut Continuation Act of 2011 (TCCA) fees									(2,432)	(2,284)	(2,096)
Operating Segments [Member] | Single-Family [Member]
Segment Reporting Information [Line Items]
Net interest income									18,013	18,162	18,212
Fee and other income									453	450	1,378
Net revenues									18,466	18,612	19,590
Investment gains, net									1,589	850	1,352
Fair value losses, net									(2,216)	1,210	(1,188)
Administrative expenses									(2,565)	(2,631)	(2,391)
Benefit for credit losses									4,038	3,313	2,090
Foreclosed property income (expense)									(523)	(604)	(540)
Credit-related income (expense)									3,515	2,709	1,550
Other expenses, net									(1,661)	(1,012)	(1,004)
Income before federal income taxes									14,696	17,454	15,813
Provision for federal income taxes									(2,859)	(3,708)	(14,301)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									11,837	13,746	1,512
Operating Segments [Member] | Multifamily [Member]
Segment Reporting Information [Line Items]
Net interest income									2,949	2,789	2,521
Fee and other income									723	529	849
Net revenues									3,672	3,318	3,370
Investment gains, net									181	102	170
Fair value losses, net									2	(89)	(23)
Administrative expenses									(458)	(428)	(346)
Benefit for credit losses									(27)	(4)	(49)
Foreclosed property income (expense)									8	(13)	19
Credit-related income (expense)									(19)	(17)	(30)
Other expenses, net									(497)	(241)	(507)
Income before federal income taxes									2,881	2,645	2,634
Provision for federal income taxes									(558)	(432)	(1,683)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									2,323	2,213	951
Operating Segments [Member] | US Treasury [Member] | Single-Family [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Cut Continuation Act of 2011 (TCCA) fees									(2,432)	(2,284)	(2,096)
Operating Segments [Member] | US Treasury [Member] | Multifamily [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Cut Continuation Act of 2011 (TCCA) fees									$ 0	$ 0	$ 0