Derivative Financial Instruments - Schedule of The Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	$ 16,674	$ 11,456
Fair value of derivative liabilities	16,136	11,153
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	16,300	11,316
Fair value of derivative liabilities	15,786	10,868
Interest-rate contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	371	135
Fair value of derivative liabilities	206	182
Derivatives not designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	15,803	10,806
Derivatives not designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	15,850	10,900
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	15,799	10,799
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	15,705	10,795
Derivatives not designated as hedging instruments | Interest-rate contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	1	2
Derivatives not designated as hedging instruments | Interest-rate contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	1	2
Derivatives not designated as hedging instruments | Other derivative contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	3	5
Derivatives not designated as hedging instruments | Other derivative contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	144	103
Derivatives designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	871	650
Derivatives designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	286	253
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	501	517
Derivatives designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	81	73
Derivatives designated as hedging instruments | Interest-rate contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	370	133
Derivatives designated as hedging instruments | Interest-rate contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	$ 205	$ 180