Derivative Instruments - Customer-Related Derivative Positions of Company (Detail) - Customer-Related Positions [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional Value, Assets	$ 96,070	$ 72,112
Fair Value, Assets	3,018	2,046
Notional Value, Liabilities	88,973	80,044
Fair Value, Liabilities	3,027	2,099
Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	51,354	32,647
Fair Value, Assets	$ 2,000	$ 1,097
Derivative Asset Average Remaining Maturity Period	5 years 2 months 27 days	5 years 8 months 9 days
Notional Value, Liabilities	$ 5,011	$ 14,068
Fair Value, Liabilities	$ 8	$ 54
Derivative Liability Average Remaining Maturity Period	3 years 3 months	4 years 8 months 16 days
Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	$ 5,224	$ 10,685
Fair Value, Assets	$ 8	$ 43
Derivative Asset Average Remaining Maturity Period	4 years 29 days	4 years 6 months 18 days
Notional Value, Liabilities	$ 50,201	$ 35,045
Fair Value, Liabilities	$ 2,056	$ 1,160
Derivative Liability Average Remaining Maturity Period	5 years 3 months 7 days	5 years 8 months 27 days
Interest Rate Contracts [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 8,676	$ 8,705
Fair Value, Assets	$ 7	$ 10
Derivative Asset Average Remaining Maturity Period	2 years 3 months 29 days	2 years 7 months 10 days
Notional Value, Liabilities	$ 321	$ 146
Fair Value, Liabilities	$ 13	$ 1
Derivative Liability Average Remaining Maturity Period	1 year 2 months 27 days	2 years 2 months 23 days
Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	$ 321	$ 146
Fair Value, Assets	$ 14	$ 2
Derivative Asset Average Remaining Maturity Period	1 year 2 months 27 days	2 years 2 months 23 days
Notional Value, Liabilities	$ 8,256	$ 8,482
Fair Value, Liabilities	$ 5	$ 9
Derivative Liability Average Remaining Maturity Period	2 years 2 months 27 days	2 years 6 months 26 days
Interest Rate Contracts [Member] | Futures [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 3,870
Fair Value, Assets	$ 2
Derivative Asset Average Remaining Maturity Period	1 year 7 days
Notional Value, Liabilities		$ 2,859
Fair Value, Liabilities		$ 2
Derivative Liability Average Remaining Maturity Period		10 months 2 days
Interest Rate Contracts [Member] | Futures [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets		$ 45
Derivative Asset Average Remaining Maturity Period		11 months 19 days
Foreign Exchange Rate Contracts [Member] | Forwards, Spots and Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	$ 24,917	$ 18,399
Fair Value, Assets	$ 938	$ 851
Derivative Asset Average Remaining Maturity Period	5 months 27 days	7 months 2 days
Notional Value, Liabilities	$ 23,476	$ 17,959
Fair Value, Liabilities	$ 896	$ 830
Derivative Liability Average Remaining Maturity Period	6 months 4 days	6 months 29 days
Foreign Exchange Option [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 1,708	$ 1,485
Fair Value, Assets	$ 49	$ 43
Derivative Asset Average Remaining Maturity Period	1 year 3 months 15 days	1 year 2 months 9 days
Foreign Exchange Option [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Liabilities	$ 1,708	$ 1,485
Fair Value, Liabilities	$ 49	$ 43
Derivative Liability Average Remaining Maturity Period	1 year 3 months 15 days	1 year 2 months 9 days