Investments in Securities Trading 1 (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	$ 34,864	$ 31,504
Mortgage-related securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	11,074	12,038
Fannie Mae [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	5,079	4,940
Freddie Mac [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	1,537	1,369
Ginnie Mae [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	239	166
Alt-A private-label securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	475	920
Subprime private-label securities [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	718	1,307
CMBS [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	2,424	2,515
Mortgage revenue bonds [Member]
Schedule of Investments in Trading Securities [Line Items]
Trading, at fair value	602	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	$ 23,790	$ 19,466