Investments in Securities Trading 1 (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 142,472	$ 48,123
Mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	6,426	8,543
Fannie Mae [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	2,750	3,424
Other agency [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	3,518	4,490
Private-label and other mortgage securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	158	629
Non-mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	136,046	39,580
U.S. Treasury securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	135,972	39,501
Other securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	74	79
Variable Interest Entity, Primary Beneficiary [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 850	$ 896