Derivative Financial Instruments - Schedule of The Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	$ 17,363	$ 25,944
Fair value of derivative liabilities	17,355	26,126
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	17,362	25,943
Fair value of derivative liabilities	17,141	25,927
Interest rate contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	1	1
Fair value of derivative liabilities	31	42
Derivatives not designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	17,218	25,939
Derivatives not designated as hedging instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	17,316	25,968
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	17,218	25,939
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	17,133	25,811
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	183	157
Derivatives designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	145	5
Derivatives designated as hedging instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	39	158
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	144	4
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	8	116
Derivatives designated as hedging instruments | Interest rate contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	1	1
Derivatives designated as hedging instruments | Interest rate contracts | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	$ 31	$ 42