Derivative Instruments and Hedging Activities - Net Gains (Losses) Related to Derivatives Designated as Cash Flow Hedges and Net Investment Hedges (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Gains (losses) recorded in AOCI	$ 32	$ 59	$ 167	$ (98)
Other Non-Interest Income
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Net derivative gains (losses) recognized in earnings	27	(15)	74	(40)
Cash flow hedges
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Gains (losses) recorded in AOCI	(39)	59	96	(98)
Gains (losses) reclassified from AOCI into earnings	29	6	74	23
Net derivative gains (losses) recognized in earnings	28	7	74	23
Cash flow hedges | Interest rate contracts
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Gains (losses) recorded in AOCI	(34)	65	112	(82)
Cash flow hedges | Interest rate contracts | Interest Income (Expense)
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Gains (losses) reclassified from AOCI into earnings	34	14	90	40
Cash flow hedges | Interest rate contracts | Other Non-Interest Income
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Gains (losses) recognized in earnings due to ineffectiveness	(1)	1	0	0
Cash flow hedges | Foreign exchange contracts
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Gains (losses) recorded in AOCI	(5)	(6)	(16)	(16)
Cash flow hedges | Foreign exchange contracts | Other Non-Interest Income
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Gains (losses) reclassified from AOCI into earnings	(5)	(8)	(16)	(17)
Net investment hedges | Foreign exchange contracts
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net [Abstract]
Gains (losses) recorded in AOCI	$ 71	$ 0	$ 71	$ 0