Regulatory Capital Requirements (Details) - USD ($)	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Component of statutory minimum capital requirement, percentage of the unpaid principal balance of outstanding Fannie Mae MBS held by third parties	0.45%
Component of critical capital requirement, percentage of the unpaid principal balance of outstanding Fannie Mae MBS held by third parties	0.45%
Net worth (deficit)	$ 14,608,000,000				$ 6,240,000,000	$ (3,686,000,000)	$ 6,071,000,000
Core capital	(106,360,000,000)				(114,919,000,000)
Statutory minimum capital requirement	22,392,000,000				22,216,000,000
Deficit of core capital over statutory minimum capital requirement	$ (128,752,000,000)				(137,135,000,000)
Component of statutory minimum capital requirement, percentage of on-balance sheet assets, except those underlying Fannie Mae MBS held by third parties	2.50%
Component of statutory minimum capital requirement, maximum percentage of other off-balance sheet obligations	0.45%
Component of critical capital requirement, percentage of on-balance sheet assets, except those underlying Fannie Mae MBS held by third parties	1.25%
Component of critical capital requirement, percentage of other off-balance sheet obligations	0.25%
Related Parties [Line Items]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 14,608,000,000				6,240,000,000
US Treasury [Member]
Related Parties [Line Items]
Aggregate funding received from US Treasury pursuant to the senior preferred stock purchase agreement	$ 119,800,000,000
Capital Reserve Amount, Fiscal Year, Senior Preferred Stock Purchase Agreement, Amendment		$ 25,000,000,000	$ 3,000,000,000	$ 0	$ 3,000,000,000.0			$ 0