Derivative Financial Instruments - Schedule of The Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	$ 15,148	$ 16,399
Fair value of derivative liabilities	15,381	16,807
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	15,140	16,386
Fair value of derivative liabilities	15,150	16,522
Interest rate contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	8	13
Fair value of derivative liabilities	49	71
Derivatives not designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	15,140	16,369
Derivatives not designated as hedging instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	15,236	16,648
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	15,140	16,369
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	15,054	16,434
Derivatives not designated as hedging instruments | Other derivative contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	0	0
Derivatives not designated as hedging instruments | Other derivative contracts | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	182	214
Derivatives designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	8	30
Derivatives designated as hedging instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	145	159
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	0	17
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	96	88
Derivatives designated as hedging instruments | Interest rate contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	8	13
Derivatives designated as hedging instruments | Interest rate contracts | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	$ 49	$ 71