Derivative Financial Instruments - Schedule of The Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	$ 11,456	$ 15,214
Fair value of derivative liabilities	11,153	15,234
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	11,316	15,135
Fair value of derivative liabilities	10,868	14,925
Interest-rate contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	135	77
Fair value of derivative liabilities	182	239
Derivatives not designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	10,806	14,643
Derivatives not designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	10,900	15,008
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	10,799	14,626
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	10,795	14,922
Derivatives not designated as hedging instruments | Interest-rate contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	2	15
Derivatives not designated as hedging instruments | Interest-rate contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	2	16
Derivatives not designated as hedging instruments | Other derivative contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	5	2
Derivatives not designated as hedging instruments | Other derivative contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	103	70
Derivatives designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	650	571
Derivatives designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	253	226
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	517	509
Derivatives designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	73	3
Derivatives designated as hedging instruments | Interest-rate contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	133	62
Derivatives designated as hedging instruments | Interest-rate contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	$ 180	$ 223