Derivative Instruments and Hedging Activities - Net Gains (Losses) Related to Derivatives Designated as Cash Flow Hedges and Net Investment Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	$ (46)	$ (54)	$ (78)	$ 727
Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains recognized in earnings	32	40	72	115
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	3	(93)	51	525
Gains (losses) reclassified from AOCI into earnings	20	49	89	147
Net derivative gains recognized in earnings	20	49	92	150
Cash flow hedges | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	(2)	(94)	37	524
Cash flow hedges | Interest rate contracts | Interest Income (Expense)
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from AOCI into earnings	15	48	76	146
Cash flow hedges | Interest rate contracts | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings due to ineffectiveness	0	0	3	3
Cash flow hedges | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	5	1	14	1
Cash flow hedges | Foreign exchange contracts | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from AOCI into earnings	5	1	13	1
Net investment hedges | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	$ (49)	$ 39	$ (129)	$ 202