Investments in Securities Trading 1 (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 39,908	$ 31,504
Mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	10,423	12,038
Fannie Mae [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	4,813	4,940
Freddie Mac [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	1,314	1,369
Ginnie Mae [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	426	166
Alt-A private-label securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	436	920
Subprime private-label securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	644	1,307
CMBS [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	2,341	2,515
Mortgage revenue bonds [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	449	722
Other mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	0	99
U.S. Treasury Securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 29,485	$ 19,466