Derivative Financial Instruments - Schedule of The Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	$ 9,170	$ 16,552
Fair value of derivative liabilities	9,394	16,684
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	9,161	16,484
Fair value of derivative liabilities	8,892	15,956
Interest-rate contracts(7)
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	9	68
Fair value of derivative liabilities	113	348
Derivatives not designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	8,783	15,982
Derivatives not designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	9,169	16,261
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	8,783	15,982
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	8,780	15,881
Derivatives not designated as hedging instruments | Other derivative contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	389	380
Derivatives designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	387	570
Derivatives designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	225	423
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	378	502
Derivatives designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	112	75
Derivatives designated as hedging instruments | Interest-rate contracts(7) | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	9	68
Derivatives designated as hedging instruments | Interest-rate contracts(7) | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	$ 113	$ 348