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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	$ 329	$ 32	$ 473	$ 167
Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains recognized in earnings	23	27	38	74
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	267	(39)	433	96
Gains (losses) reclassified from AOCI into earnings	37	29	122	74
Net derivative gains recognized in earnings	39	28	126	74
Cash flow hedges | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	270	(34)	447	112
Cash flow hedges | Interest rate contracts | Interest Income (Expense)
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from AOCI into earnings	39	34	136	90
Cash flow hedges | Interest rate contracts | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in earnings due to ineffectiveness	2	(1)	4	0
Cash flow hedges | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	(3)	(5)	(14)	(16)
Cash flow hedges | Foreign exchange contracts | Other Non-Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from AOCI into earnings	(2)	(5)	(14)	(16)
Net investment hedges | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recorded in AOCI	$ 62	$ 71	$ 40	$ 71