Impact of Derivative Instruments on Income Statement (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Fair Value Hedging | Interest Rate Contract | Net Interest Revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in income on derivatives	$ (249)	$ 127	$ 95	$ (122)	$ 16
Amount of gain or (loss) recognized in hedged item	248	(127)	(97)	121	(24)
Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	90	342	97	432	(396)
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)	88	339	104	427	(395)
Amount of gain or (loss) recognized in income on derivatives (ineffectiveness portion and amount excluded from effectiveness testing)		0.1		0.1	(0.1)
Cash Flow Hedging | Foreign Exchange Contract | Net Interest Revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	9	(2)	(56)	7	(61)
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)	8	(4)	(50)	4	(61)
Cash Flow Hedging | Foreign Exchange Contract | Other Revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	(1)	3	(3)	2	(8)
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)	(1)	2	(3)	1	(4)
Amount of gain or (loss) recognized in income on derivatives (ineffectiveness portion and amount excluded from effectiveness testing)		0.1		0.1	(0.1)
Cash Flow Hedging | Foreign Exchange Contract | Trading Revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	81	342	155	423	(331)
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)	81	342	156	423	(331)
Cash Flow Hedging | Foreign Exchange Contract | Salary Expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	1	(1)	1		4
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)		(1)	1	(1)	1
Net Investment Hedging | Foreign Exchange Contract
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	110	(139)	(12)	(29)	(181)
Net Investment Hedging | Foreign Exchange Contract | Other Revenue
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in income on derivatives (ineffectiveness portion and amount excluded from effectiveness testing)		$ (0.1)		$ (0.1)	$ (0.1)