Derivative Instruments - Customer-Related Derivative Positions of Company (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Fair Value, Assets	$ 1,362	$ 1,546
Fair Value, Liabilities	1,825	2,178
Customer-Related Positions [Member]
Derivative [Line Items]
Notional Value, Assets	32,809	33,440
Fair Value, Assets	1,261	1,443
Notional Value, Liabilities	33,070	33,013
Fair Value, Liabilities	1,174	1,365
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	13,562	16,671
Fair Value, Assets	736	1,085
Derivative Asset Average Remaining Maturity Period	5 years 3 months 18 days	4 years 9 months 11 days
Notional Value, Liabilities	5,138	1,090
Fair Value, Liabilities	70	15
Derivative Liability Average Remaining Maturity Period	4 years 11 months 23 days	9 years 3 months 18 days
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	4,700	928
Fair Value, Assets	76	14
Derivative Asset Average Remaining Maturity Period	5 years 1 month 24 days	11 years 1 month 13 days
Notional Value, Liabilities	14,089	16,923
Fair Value, Liabilities	691	1,042
Derivative Liability Average Remaining Maturity Period	5 years 3 months 4 days	4 years 8 months 27 days
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	3,681	3,046
Fair Value, Assets	28	16
Derivative Asset Average Remaining Maturity Period	4 years 5 months 16 days	5 years 2 months 27 days
Notional Value, Liabilities	107	28
Fair Value, Liabilities	1
Derivative Liability Average Remaining Maturity Period	1 year 1 month 13 days	4 years 5 months 1 day
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	107	286
Fair Value, Assets	1
Derivative Asset Average Remaining Maturity Period	1 year 1 month 13 days	9 months
Notional Value, Liabilities	3,681	2,788
Fair Value, Liabilities	28	16
Derivative Liability Average Remaining Maturity Period	4 years 5 months 16 days	5 years 8 months 5 days
Customer-Related Positions [Member] | Foreign Exchange Contract [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	367	323
Fair Value, Assets	9	6
Derivative Asset Average Remaining Maturity Period	7 months 21 days	6 months 18 days
Notional Value, Liabilities
Fair Value, Liabilities
Derivative Liability Average Remaining Maturity Period
Customer-Related Positions [Member] | Foreign Exchange Contract [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets
Fair Value, Assets
Notional Value, Liabilities	367	323
Fair Value, Liabilities	9	6
Derivative Liability Average Remaining Maturity Period	7 months 21 days	6 months 18 days
Customer-Related Positions [Member] | Foreign Exchange Contract [Member] | Forwards, Spots and Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	10,392	12,186
Fair Value, Assets	411	322
Derivative Asset Average Remaining Maturity Period	8 months 16 days	5 months 5 days
Notional Value, Liabilities	9,688	11,861
Fair Value, Liabilities	$ 375	$ 286
Derivative Liability Average Remaining Maturity Period	8 months 5 days	5 months 9 days