Offsetting Arrangements - Assets With Offsetting Arrangements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	$ 16,260	$ 15,214
Derivatives, Gross Amounts Offset in Statement of Condition	(8,212)	(7,280)
Net Amounts of Assets Presented in Statement of Condition	8,048	7,934
Derivative, Collateral, Cash Offset	(466)	(983)
Total Net Derivative Asset	8,048	7,934
Resale Agreements and Securities Borrowing, Gross Amounts of Recognized Assets	62,587	47,488
Resale Agreements and Securities Borrowing, Gross Amounts Offset in Statement of Condition	(31,407)	(29,157)
Net Amounts of Assets Presented in Statement of Condition	31,180	18,331
Total, Gross Amounts of Recognized Assets	78,847	62,702
Total, Gross Amounts Offset in Statement of Condition	(39,619)	(36,437)
Total, Net Amounts of Assets Presented in Statement of Condition	39,228	26,265
Securities purchased under resale agreements	11,331	2,390
Securities borrowed subject to master netting arrangements	19,849	15,941
Foreign exchange contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	16,116	15,135
Derivatives, Gross Amounts Offset in Statement of Condition	(7,730)	(6,275)
Net Amounts of Assets Presented in Statement of Condition	8,386	8,860
Interest-rate contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	141	77
Derivatives, Gross Amounts Offset in Statement of Condition	(14)	(21)
Net Amounts of Assets Presented in Statement of Condition	127	56
Other derivative contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	3	2
Derivatives, Gross Amounts Offset in Statement of Condition	(2)	(1)
Net Amounts of Assets Presented in Statement of Condition	$ 1	$ 1