Derivative Instruments - Customer-Related Derivative Positions of Company (Detail) (Customer-Related Positions [Member], USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Derivative [Line Items]
Notional Value, Assets	$ 44,277	$ 33,286
Fair Value, Assets	1,326	1,215
Notional Value, Liabilities	43,107	33,480
Fair Value, Liabilities	1,292	1,137
Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	16,055	11,717
Fair Value, Assets	645	600
Derivative Asset Average Remaining Maturity Period	5 years 11 months 9 days	5 years 1 month 10 days
Notional Value, Liabilities	8,509	7,291
Fair Value, Liabilities	47	106
Derivative Liability Average Remaining Maturity Period	4 years 3 months 29 days	5 years 6 months 26 days
Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	7,215	6,746
Fair Value, Assets	54	114
Derivative Asset Average Remaining Maturity Period	3 years 11 months 23 days	6 years 11 days
Notional Value, Liabilities	16,384	12,361
Fair Value, Liabilities	638	560
Derivative Liability Average Remaining Maturity Period	5 years 10 months 10 days	4 years 10 months 24 days
Interest Rate Contracts [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	4,110	3,489
Fair Value, Assets	10	33
Derivative Asset Average Remaining Maturity Period	3 years 10 months 2 days	4 years 6 months 11 days
Notional Value, Liabilities	24
Fair Value, Liabilities
Derivative Liability Average Remaining Maturity Period	2 years 8 months 1 day
Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	24
Fair Value, Assets
Derivative Asset Average Remaining Maturity Period	2 years 8 months 1 day
Notional Value, Liabilities	4,096	3,489
Fair Value, Liabilities	10	33
Derivative Liability Average Remaining Maturity Period	3 years 10 months 6 days	4 years 6 months 11 days
Interest Rate Contracts [Member] | Futures [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	2,439
Fair Value, Assets
Derivative Asset Average Remaining Maturity Period	3 months
Notional Value, Liabilities
Fair Value, Liabilities
Derivative Liability Average Remaining Maturity Period
Interest Rate Contracts [Member] | Futures [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	334
Fair Value, Assets
Derivative Asset Average Remaining Maturity Period	1 year 3 months 11 days
Notional Value, Liabilities	131
Fair Value, Liabilities
Derivative Liability Average Remaining Maturity Period	11 months 16 days
Foreign Exchange Rate Contracts [Member] | Forwards, Spots and Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	13,349	10,970
Fair Value, Assets	595	457
Derivative Asset Average Remaining Maturity Period	6 months 18 days	7 months 2 days
Notional Value, Liabilities	13,212	9,975
Fair Value, Liabilities	575	427
Derivative Liability Average Remaining Maturity Period	6 months 18 days	7 months 13 days
Foreign Exchange Option [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	751	364
Fair Value, Assets	22	11
Derivative Asset Average Remaining Maturity Period	6 months 26 days	6 months 11 days
Notional Value, Liabilities
Fair Value, Liabilities
Derivative Liability Average Remaining Maturity Period
Foreign Exchange Option [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets
Fair Value, Assets
Derivative Asset Average Remaining Maturity Period	0 years
Notional Value, Liabilities	751	364
Fair Value, Liabilities	$ 22	$ 11
Derivative Liability Average Remaining Maturity Period	6 months 26 days	6 months 11 days