Customer-Related Derivative Positions of Company (Detail) (Customer-Related Positions, USD $) In Millions, unless otherwise specified	Sep. 30, 2012 Y		Dec. 31, 2011 Y
Interest rate contracts | Receive fixed/pay floating swaps
Derivative [Line Items]
Notional Value, Assets	$ 17,262		$ 16,230
Fair Value, Assets	1,186		1,216
Derivative Asset Average Remaining Maturity Period	4.74		4.98
Notional Value, Liabilities	359		523
Fair Value, Liabilities	8		1
Derivative Liability Average Remaining Maturity Period	16.45		2.52
Interest rate contracts | Pay fixed/receive floating swaps
Derivative [Line Items]
Notional Value, Assets	280		99
Fair Value, Assets	8
Derivative Asset Average Remaining Maturity Period	19.79		1.81
Notional Value, Liabilities	17,433		16,206
Fair Value, Liabilities	1,148		1,182
Derivative Liability Average Remaining Maturity Period	4.76		5.10
Interest rate contracts | Purchased options
Derivative [Line Items]
Notional Value, Assets	3,014		2,660
Fair Value, Assets	15		26
Derivative Asset Average Remaining Maturity Period	5.34		6.11
Notional Value, Liabilities	28
Derivative Liability Average Remaining Maturity Period	4.67
Interest rate contracts | Written options
Derivative [Line Items]
Notional Value, Assets	202
Derivative Asset Average Remaining Maturity Period	0.73
Notional Value, Liabilities	2,839		2,660
Fair Value, Liabilities	15		26
Derivative Liability Average Remaining Maturity Period	5.66		6.11
Foreign exchange contract | Purchased options
Derivative [Line Items]
Notional Value, Assets	346		127
Fair Value, Assets	8		5
Derivative Asset Average Remaining Maturity Period	0.65		0.41
Foreign exchange contract | Written options
Derivative [Line Items]
Notional Value, Liabilities	346		127
Fair Value, Liabilities	8		5
Derivative Liability Average Remaining Maturity Period	0.65		0.41
Foreign exchange contract | Forwards, spots and swaps
Derivative [Line Items]
Notional Value, Assets	11,038	[1]	7,936	[1]
Fair Value, Assets	301	[1]	369	[1]
Derivative Asset Average Remaining Maturity Period	0.36	[1]	0.54	[1]
Notional Value, Liabilities	10,799	[1]	7,731	[1]
Fair Value, Liabilities	$ 283	[1]	$ 354	[1]
Derivative Liability Average Remaining Maturity Period	0.45	[1]	0.54	[1]

[1] Reflects the net of long and short positions.