Investments in Securities Trading 1 (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 40,899	$ 41,867
Mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	5,795	6,276
Fannie Mae [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	1,583	1,467
Other agency [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	3,158	3,503
Alt-A and subprime private-label securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	1,054	1,306
Non-mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	35,104	35,591
U.S. Treasury securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	35,020	35,502
Other securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 84	$ 89