Investments in Securities Trading 1 (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 39,167	$ 39,908
Mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	9,515	10,423
Fannie Mae [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	5,352	4,813
Freddie Mac [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	1,328	1,314
Ginnie Mae [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	542	426
Alt-A private-label securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	316	436
Subprime private-label securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	395	644
CMBS [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	1,389	2,341
Mortgage revenue bonds [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	193	449
U.S. Treasury securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 29,652	$ 29,485