Derivative Financial Instruments - Schedule of The Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	$ 21,380	$ 11,456
Fair value of derivative liabilities	20,993	11,153
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	20,868	11,316
Fair value of derivative liabilities	20,620	10,868
Interest-rate contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	507	135
Fair value of derivative liabilities	212	182
Derivatives not designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	20,478	10,806
Derivatives not designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	20,684	10,900
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	20,472	10,799
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	20,522	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	5	5
Derivatives not designated as hedging instruments | Other derivative contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	161	103
Derivatives designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	902	650
Derivatives designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	309	253
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	396	517
Derivatives designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	98	73
Derivatives designated as hedging instruments | Interest-rate contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	506	133
Derivatives designated as hedging instruments | Interest-rate contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	$ 211	$ 180