Segment Reporting (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net interest income	$ 4,973	$ 5,369	$ 5,377	$ 5,232	$ 5,111	$ 5,274	$ 5,002	$ 5,346	$ 20,951	$ 20,733	$ 21,295
Fee and other income									979	2,227	966
Net revenues									21,930	22,960	22,261
Investment gains, net	259	166	277	250	833	313	385	(9)	952	1,522	1,256
Fair value losses, net	(539)	386	229	1,045	(191)	(289)	(691)	(40)	1,121	(1,211)	(1,081)
Administrative expenses	(814)	(740)	(755)	(750)	(703)	(664)	(686)	(684)	(3,059)	(2,737)	(2,741)
Benefit for credit losses	1,080	716	1,296	217	560	(182)	1,267	396	3,309	2,041	2,155
Foreclosed property income (expense)	(157)	(159)	(139)	(162)	(130)	(140)	(34)	(217)	(617)	(521)	(644)
Credit-related income (expense)									2,692	1,520	1,511
Temporary Payroll Cut Continuation Act of 2011 (TCCA) fees	(586)	(576)	(565)	(557)	(544)	(531)	(518)	(503)	(2,284)	(2,096)	(1,845)
Other expenses, net	(307)	(377)	(366)	(203)	(411)	(427)	(291)	(382)	(1,253)	(1,511)	(1,028)
Income before federal income taxes	4,058	5,056	5,593	5,392	4,956	4,548	4,787	4,156	20,099	18,447	18,333
Provision for federal income taxes	(828)	(1,045)	(1,136)	(1,131)	(11,489)	(1,525)	(1,587)	(1,383)	(4,140)	(15,984)	(6,020)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 3,230	$ 4,011	$ 4,457	$ 4,261	$ (6,533)	$ 3,023	$ 3,200	$ 2,773	15,959	2,463	12,313
US Treasury [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Cut Continuation Act of 2011 (TCCA) fees									(2,284)	(2,096)	(1,845)
Operating Segments [Member] | Single-Family [Member]
Segment Reporting Information [Line Items]
Net interest income									18,162	18,212	19,010
Fee and other income									450	1,378	521
Net revenues									18,612	19,590	19,531
Investment gains, net									850	1,352	944
Fair value losses, net									1,210	(1,188)	(1,040)
Administrative expenses									(2,631)	(2,391)	(2,418)
Benefit for credit losses									3,313	2,090	2,092
Foreclosed property income (expense)									(604)	(540)	(653)
Credit-related income (expense)									2,709	1,550	1,439
Other expenses, net									(1,012)	(1,004)	(1,012)
Income before federal income taxes									17,454	15,813	15,599
Provision for federal income taxes									(3,708)	(14,301)	(5,417)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									13,746	1,512	10,182
Operating Segments [Member] | Multifamily [Member]
Segment Reporting Information [Line Items]
Net interest income									2,789	2,521	2,285
Fee and other income									529	849	445
Net revenues									3,318	3,370	2,730
Investment gains, net									102	170	312
Fair value losses, net									(89)	(23)	(41)
Administrative expenses									(428)	(346)	(323)
Benefit for credit losses									(4)	(49)	63
Foreclosed property income (expense)									(13)	19	9
Credit-related income (expense)									(17)	(30)	72
Other expenses, net									(241)	(507)	(16)
Income before federal income taxes									2,645	2,634	2,734
Provision for federal income taxes									(432)	(1,683)	(603)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest									2,213	951	2,131
Operating Segments [Member] | US Treasury [Member] | Single-Family [Member]
Segment Reporting Information [Line Items]
Temporary Payroll Cut Continuation Act of 2011 (TCCA) fees									(2,284)	(2,096)	(1,845)
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