Offsetting Arrangements - Assets With Offsetting Arrangements (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	$ 10,971	$ 15,214
Derivatives, Gross Amounts Offset in Statement of Condition	(5,584)	(7,280)
Net Amounts of Assets Presented in Statement of Condition	5,387	7,934
Derivative, Collateral, Cash Offset	(842)	(983)
Total Net Derivative Asset	5,387	7,934
Resale Agreements and Securities Borrowing, Gross Amounts of Recognized Assets	67,065	47,488
Resale Agreements and Securities Borrowing, Gross Amounts Offset in Statement of Condition	(36,705)	(29,157)
Net Amounts of Assets Presented in Statement of Condition	30,360	18,331
Total, Gross Amounts of Recognized Assets	78,036	62,702
Total, Gross Amounts Offset in Statement of Condition	(42,289)	(36,437)
Total, Net Amounts of Assets Presented in Statement of Condition	35,747	26,265
Securities purchased under resale agreements	9,155	2,390
Securities borrowed subject to master netting arrangements	21,205	15,941
Foreign exchange contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	10,734	15,135
Derivatives, Gross Amounts Offset in Statement of Condition	(4,729)	(6,275)
Net Amounts of Assets Presented in Statement of Condition	6,005	8,860
Interest-rate contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	232	77
Derivatives, Gross Amounts Offset in Statement of Condition	(9)	(21)
Net Amounts of Assets Presented in Statement of Condition	223	56
Equity Derivative Contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	1	0
Derivatives, Gross Amounts Offset in Statement of Condition	(1)	0
Net Amounts of Assets Presented in Statement of Condition	0	0
Other Derivative Contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	4	2
Derivatives, Gross Amounts Offset in Statement of Condition	(3)	(1)
Net Amounts of Assets Presented in Statement of Condition	$ 1	$ 1