Derivative Instruments- Impact of Derivative Instruments on Income Statement (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Fair Value Hedging | Interest rate contracts | Net interest revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized in income on derivatives	$ (200)	$ (109)	$ 143	$ (594)	$ 388
Gain or (loss) recognized in hedged item	195	102	(137)	574	(374)
Cash flow hedges
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized in accumulated OCI on derivatives (effective portion)	16	(4)	(57)	18	127
Gain or (loss) reclassified from accumulated OCI into income (effective portion)	31	(1)	(74)	34	123
Gain or (loss) recognized in income on derivatives (ineffectiveness portion and amount excluded from effectiveness testing)	0.2	(0.2)	(0.2)	0.1	(0.1)
Cash flow hedges | Foreign exchange contracts | Net interest revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized in accumulated OCI on derivatives (effective portion)	0	(1)	4	(2)	(23)
Gain or (loss) reclassified from accumulated OCI into income (effective portion)	(1)	0	(5)	(2)	(24)
Gain or (loss) recognized in income on derivatives (ineffectiveness portion and amount excluded from effectiveness testing)	0	0	0	0	0
Cash flow hedges | Foreign exchange contracts | Other revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized in accumulated OCI on derivatives (effective portion)	(5)	0	(5)	(2)	(4)
Gain or (loss) reclassified from accumulated OCI into income (effective portion)	1	1	(1)	2	(1)
Gain or (loss) recognized in income on derivatives (ineffectiveness portion and amount excluded from effectiveness testing)	0.2	(0.2)	(0.2)	0.1	(0.1)
Cash flow hedges | Foreign exchange contracts | Trading revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized in accumulated OCI on derivatives (effective portion)	29	(6)	(67)	26	150
Gain or (loss) reclassified from accumulated OCI into income (effective portion)	29	(6)	(67)	26	150
Gain or (loss) recognized in income on derivatives (ineffectiveness portion and amount excluded from effectiveness testing)	0	0	0	0	0
Cash flow hedges | Foreign exchange contracts | Salary expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized in accumulated OCI on derivatives (effective portion)	(8)	3	11	(4)	4
Gain or (loss) reclassified from accumulated OCI into income (effective portion)	2	4	(1)	8	(2)
Gain or (loss) recognized in income on derivatives (ineffectiveness portion and amount excluded from effectiveness testing)	0	0	0	0	0
Net Investment Hedging | Foreign exchange contracts | Net interest revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized in accumulated OCI on derivatives (effective portion)	308	(129)	(192)	163	13
Gain or (loss) reclassified from accumulated OCI into income (effective portion)	0	(1)	2	(1)	2
Net Investment Hedging | Foreign exchange contracts | Other revenue
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (loss) recognized in income on derivatives (ineffectiveness portion and amount excluded from effectiveness testing)	$ (0.2)	$ 0.2	$ 0	$ (0.1)	$ 0.1