Offsetting Arrangements - Assets With Offsetting Arrangements (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	$ 11,740	$ 16,552
Derivatives, Gross Amounts Offset in Statement of Condition	(7,028)	(9,231)
Derivatives, Net Amounts of Assets Presented in Statement of Condition	4,712	7,321
Derivatives, Net Amount	4,606	7,074
Derivatives, Cash collateral and securities netting, offset	(637)	(906)
Derivatives, Cash collateral and securities netting, Cash and Securities Received	(106)	(247)
Derivatives, Cash collateral and securities netting, Net	(743)	(1,153)
Resale agreements and securities borrowing, Gross Amounts of Recognized Assets	63,821	58,677
Resale agreements and securities borrowing, Gross Amounts Offset in Statement of Condition	(36,728)	(35,517)
Resale agreements and securities borrowing, Net Amounts of Assets Presented in Statement of Condition	27,093	23,160
Resale agreements and securities borrowing, Cash and Securities Received	(27,093)	(22,939)
Resale agreements and securities borrowing, Net Amount	0	221
Total derivatives and other financial instruments, Gross Amounts of Recognized Assets	75,561	75,229
Total derivatives and other financial instruments, Gross Amounts Offset in Statement of Condition	(43,756)	(44,748)
Total derivatives and other financial instruments, Net Amounts of Assets Presented in Statement of Condition	31,805	30,481
Total derivatives and other financial instruments, Cash and Securities Received(5)	(27,199)	(23,186)
Total derivatives and other financial instruments, Net Amount	4,606	7,295
Securities purchased under resale agreements	3,465	1,956
Securities borrowed subject to master netting arrangements	(23,628)	(21,204)
Foreign exchange contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	11,737	16,484
Derivatives, Gross Amounts Offset in Statement of Condition	(6,389)	(8,257)
Derivatives, Net Amounts of Assets Presented in Statement of Condition	5,348	8,227
Derivatives, Net Amount	5,348	8,227
Interest-rate contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	3	68
Derivatives, Gross Amounts Offset in Statement of Condition	(2)	(68)
Derivatives, Net Amounts of Assets Presented in Statement of Condition	1	0
Derivatives, Net Amount	$ 1	$ 0