Derivative Instruments - Customer-Related Derivative Positions of Company (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Fair Value, Assets	$ 2,035	$ 1,546
Fair Value, Liabilities	1,956	2,178
Customer-Related Positions [Member]
Derivative [Line Items]
Notional Value, Assets	32,284	33,440
Fair Value, Assets	1,410	1,443
Notional Value, Liabilities	30,881	33,013
Fair Value, Liabilities	1,329	1,365
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	12,603	16,671
Fair Value, Assets	753	1,085
Derivative Asset Average Remaining Maturity Period	5 years 26 days	4 years 9 months 11 days
Notional Value, Liabilities	5,175	1,090
Fair Value, Liabilities	93	15
Derivative Liability Average Remaining Maturity Period	5 years 3 months 11 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	5,463	928
Fair Value, Assets	100	14
Derivative Asset Average Remaining Maturity Period	5 years 3 months 7 days	11 years 1 month 13 days
Notional Value, Liabilities	12,404	16,923
Fair Value, Liabilities	711	1,042
Derivative Liability Average Remaining Maturity Period	5 years 1 month 2 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	3,548	3,046
Fair Value, Assets	27	16
Derivative Asset Average Remaining Maturity Period	4 years 7 months 13 days	5 years 2 months 27 days
Notional Value, Liabilities		28
Derivative Liability Average Remaining Maturity Period		4 years 5 months 1 day
Customer-Related Positions [Member] | Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	28	286
Derivative Asset Average Remaining Maturity Period	3 years 11 months 1 day	9 months
Notional Value, Liabilities	3,475	2,788
Fair Value, Liabilities	27	16
Derivative Liability Average Remaining Maturity Period	4 years 8 months 5 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	245	323
Fair Value, Assets	4	6
Derivative Asset Average Remaining Maturity Period	5 months 27 days	6 months 18 days
Derivative Liability Average Remaining Maturity Period	0 years	0 years
Customer-Related Positions [Member] | Foreign Exchange Contract [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Liabilities	245	323
Fair Value, Liabilities	4	6
Derivative Liability Average Remaining Maturity Period	5 months 27 days	6 months 18 days
Customer-Related Positions [Member] | Foreign Exchange Contract [Member] | Forwards, Spots and Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	10,397	12,186
Fair Value, Assets	526	322
Derivative Asset Average Remaining Maturity Period	6 months 26 days	5 months 5 days
Notional Value, Liabilities	9,582	11,861
Fair Value, Liabilities	$ 494	$ 286
Derivative Liability Average Remaining Maturity Period	6 months 26 days	5 months 9 days