Consolidations and Transfers of Financial Assets Unconsolidated VIEs (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Assets and liabilities recorded in our condensed consolidated balance sheets related to mortgage-backed trusts: [Abstract]
Trading, at fair value	$ 34,864	$ 31,504
Available-for-sale, at fair value	24,161	30,654
Other assets	19,138	19,992
Other liabilities	(10,661)	(12,019)
Unconsolidated VIEs [Member] | Mortgage-Backed Trusts [Member]
Assets and liabilities recorded in our condensed consolidated balance sheets related to mortgage-backed trusts: [Abstract]
Trading, at fair value	10,922	11,863
Available-for-sale, at fair value	22,069	27,819
Other assets	106	111
Other liabilities	(856)	(1,440)
Net carrying amount	32,241	38,353
Maximum exposure to loss	38,586	45,311
Total assets of unconsolidated mortgage-backed trusts	234,062	253,554
Unconsolidated VIEs [Member] | Limited Partnership Investments [Member]
Assets and liabilities recorded in our condensed consolidated balance sheets related to mortgage-backed trusts: [Abstract]
Total assets of unconsolidated mortgage-backed trusts	5,200	5,800
Fannie Mae Securities [Member]
Assets and liabilities recorded in our condensed consolidated balance sheets related to mortgage-backed trusts: [Abstract]
Trading, at fair value	4,948	4,790
Available-for-sale, at fair value	4,219	5,043
Non-Fannie Mae Securities [Member]
Assets and liabilities recorded in our condensed consolidated balance sheets related to mortgage-backed trusts: [Abstract]
Trading, at fair value	5,974	7,073
Available-for-sale, at fair value	$ 17,850	$ 22,776