Offsetting Arrangements - Assets With Offsetting Arrangements (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	$ 17,382	$ 11,606
Derivatives, Gross Amounts Offset in Statement of Condition	(11,231)	(7,593)
Derivatives, Net Amounts of Assets Presented in Statement of Condition	6,151	4,013
Derivatives, Net Amount	6,051	3,889
Derivatives, Cash collateral and securities netting, offset	(1,557)	(2,045)
Derivatives, Cash collateral and securities netting, Cash and Securities Received	(100)	(124)
Derivatives, Cash collateral and securities netting, Net	(1,657)	(2,169)
Resale agreements and securities borrowing, Gross Amounts of Recognized Assets	73,482	70,079
Resale agreements and securities borrowing, Gross Amounts Offset in Statement of Condition	(47,108)	(47,434)
Resale agreements and securities borrowing, Net Amounts of Assets Presented in Statement of Condition	26,372	22,645
Resale agreements and securities borrowing, Cash and Securities Received	(26,063)	(22,645)
Resale agreements and securities borrowing, Net Amount	310	0
Total derivatives and other financial instruments, Gross Amounts of Recognized Assets	90,864	81,685
Total derivatives and other financial instruments, Gross Amounts Offset in Statement of Condition	(58,339)	(55,027)
Total derivatives and other financial instruments, Net Amounts of Assets Presented in Statement of Condition	32,523	26,658
Total derivatives and other financial instruments, Cash and Securities Received(5)	(26,163)	(22,769)
Total derivatives and other financial instruments, Net Amount	6,361	3,889
Securities purchased under resale agreements	3,583	3,241
Cash collateral provided for securities lending	22,789	19,400
Securities borrowed subject to master netting arrangements		(19,404)
Foreign exchange contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	17,380	11,597
Derivatives, Gross Amounts Offset in Statement of Condition	(9,674)	(5,548)
Derivatives, Net Amounts of Assets Presented in Statement of Condition	7,706	6,049
Derivatives, Net Amount	7,706	6,049
Interest-rate contracts(6)
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	0	8
Derivatives, Gross Amounts Offset in Statement of Condition	0	0
Derivatives, Net Amounts of Assets Presented in Statement of Condition	0	8
Derivatives, Net Amount	0	8
Other derivative contracts
Offsetting Assets [Line Items]
Derivatives, Gross Amounts of Recognized Assets	2	1
Derivatives, Gross Amounts Offset in Statement of Condition	0	0
Derivatives, Net Amounts of Assets Presented in Statement of Condition	2	1
Derivatives, Net Amount	$ 2	$ 1