Impact of Derivative Instruments on Income Statement (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 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	$ 127	$ (192)	$ (79)
Amount of gain or (loss) recognized in hedged item	(127)	185	73
Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in OCI on derivative (effective portion)	342	(18)	(493)
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)	339	31	(499)
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)	(2)	(61)	(5)
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)	(4)	(10)	(11)
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)	3
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)	2	(2)	3
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)	342	43	(491)
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)	342	43	(491)
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)		3
Amount of gain or (loss) reclassified from accumulated OCI into income (effective portion)	(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)	(139)	36	(169)
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