Derivative Instruments - Customer-Related Derivative Positions of Company (Detail) - Customer-Related Positions [Member] - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional Value, Assets	$ 109,768	$ 72,112
Fair Value, Assets	3,706	2,046
Notional Value, Liabilities	101,871	80,044
Fair Value, Liabilities	3,777	2,099
Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	55,987	32,647
Fair Value, Assets	$ 2,617	$ 1,097
Derivative Asset Average Remaining Maturity Period	5 years 4 months 13 days	5 years 8 months 9 days
Notional Value, Liabilities	$ 13,198	$ 14,068
Fair Value, Liabilities	$ 9	$ 54
Derivative Liability Average Remaining Maturity Period	1 year 4 months 21 days	4 years 8 months 16 days
Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	$ 12,868	$ 10,685
Fair Value, Assets	$ 7	$ 43
Derivative Asset Average Remaining Maturity Period	1 year 7 months 17 days	4 years 6 months 18 days
Notional Value, Liabilities	$ 55,594	$ 35,045
Fair Value, Liabilities	$ 2,722	$ 1,160
Derivative Liability Average Remaining Maturity Period	5 years 4 months 17 days	5 years 8 months 27 days
Interest Rate Contracts [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 9,416	$ 8,705
Fair Value, Assets	$ 12	$ 10
Derivative Asset Average Remaining Maturity Period	2 years 4 months 13 days	2 years 7 months 10 days
Notional Value, Liabilities	$ 375	$ 146
Fair Value, Liabilities	$ 27	$ 1
Derivative Liability Average Remaining Maturity Period	1 year 11 days	2 years 2 months 23 days
Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	$ 375	$ 146
Fair Value, Assets	$ 29	$ 2
Derivative Asset Average Remaining Maturity Period	1 year 11 days	2 years 2 months 23 days
Notional Value, Liabilities	$ 8,695	$ 8,482
Fair Value, Liabilities	$ 7	$ 9
Derivative Liability Average Remaining Maturity Period	2 years 2 months 23 days	2 years 6 months 26 days
Interest Rate Contracts [Member] | Futures [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 6,176
Fair Value, Assets	$ 4
Derivative Asset Average Remaining Maturity Period	1 year 1 month 6 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	$ 22,998	$ 18,399
Fair Value, Assets	$ 981	$ 851
Derivative Asset Average Remaining Maturity Period	6 months 15 days	7 months 2 days
Notional Value, Liabilities	$ 22,061	$ 17,959
Fair Value, Liabilities	$ 956	$ 830
Derivative Liability Average Remaining Maturity Period	6 months 18 days	6 months 29 days
Foreign Exchange Option [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 1,948	$ 1,485
Fair Value, Assets	$ 56	$ 43
Derivative Asset Average Remaining Maturity Period	1 year 2 months 16 days	1 year 2 months 9 days
Foreign Exchange Option [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Liabilities	$ 1,948	$ 1,485
Fair Value, Liabilities	$ 56	$ 43
Derivative Liability Average Remaining Maturity Period	1 year 2 months 16 days	1 year 2 months 9 days