Derivative Instruments - Customer-Related Derivative Positions of Company (Detail) (Customer-Related Positions [Member], USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Notional Value, Assets	$ 56,695	$ 50,780
Fair Value, Assets	2,574	1,853
Notional Value, Liabilities	54,876	47,993
Fair Value, Liabilities	2,482	1,717
Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	29,287	21,724
Fair Value, Assets	1,140	888
Derivative Asset Average Remaining Maturity Period	5 years 7 months 28 days	6 years 1 month 2 days
Notional Value, Liabilities	3,634	5,880
Fair Value, Liabilities	10	24
Derivative Liability Average Remaining Maturity Period	5 years 5 months 9 days	3 years 9 months 15 days
Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	2,773	4,622
Fair Value, Assets	8	26
Derivative Asset Average Remaining Maturity Period	4 years 11 months 19 days	3 years 3 months 7 days
Notional Value, Liabilities	27,960	21,821
Fair Value, Liabilities	1,166	892
Derivative Liability Average Remaining Maturity Period	5 years 8 months 16 days	6 years 29 days
Interest Rate Contracts [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	4,114	4,409
Fair Value, Assets	8	10
Derivative Asset Average Remaining Maturity Period	3 years 10 months 28 days	3 years 9 months 15 days
Notional Value, Liabilities	23	24
Derivative Liability Average Remaining Maturity Period	2 years 2 months 1 day	2 years 5 months 1 day
Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	23	24
Derivative Asset Average Remaining Maturity Period	2 years 2 months 1 day	2 years 5 months 1 day
Notional Value, Liabilities	4,080	4,375
Fair Value, Liabilities	7	10
Derivative Liability Average Remaining Maturity Period	3 years 10 months 28 days	3 years 9 months 15 days
Interest Rate Contracts [Member] | Futures [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	1,796	1,811
Derivative Asset Average Remaining Maturity Period	3 months	2 months 19 days
Notional Value, Liabilities		226
Derivative Liability Average Remaining Maturity Period		5 months 12 days
Interest Rate Contracts [Member] | Futures [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets		152
Derivative Asset Average Remaining Maturity Period		1 year 29 days
Notional Value, Liabilities	807	46
Derivative Liability Average Remaining Maturity Period	1 year 2 months 27 days	1 year 8 months 23 days
Foreign Exchange Rate Contracts [Member] | Forwards, Spots and Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	17,250	17,062
Fair Value, Assets	1,327	890
Derivative Asset Average Remaining Maturity Period	8 months 5 days	6 months 7 days
Notional Value, Liabilities	16,920	14,645
Fair Value, Liabilities	1,208	752
Derivative Liability Average Remaining Maturity Period	8 months 9 days	7 months 2 days
Foreign Exchange Option [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	1,452	976
Fair Value, Assets	91	39
Derivative Asset Average Remaining Maturity Period	1 year 7 days	5 months 9 days
Foreign Exchange Option [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Liabilities	1,452	976
Fair Value, Liabilities	$ 91	$ 39
Derivative Liability Average Remaining Maturity Period	1 year 7 days	5 months 9 days