Investments in Securities Trading 1 (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 48,123		$ 41,867
Mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	8,543		6,276
Fannie Mae [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	3,424		1,467
Variable Interest Entity, Conclusion to Consolidate, Change in Facts and Circumstances, Amount		$ 1,400
Other agency [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	4,490		3,503
Alt-A and subprime private-label securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	629		1,306
U.S. Treasury Securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	39,501		35,502
Debt Security, Corporate, US [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	79		89
Non-mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 39,580		$ 35,591