Derivative Financial Instruments - Schedule of The Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	$ 21,899	$ 25,944
Fair value of derivative liabilities	22,261	26,126
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	21,898	25,943
Fair value of derivative liabilities	22,045	25,927
Interest rate contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	1	1
Fair value of derivative liabilities	35	42
Derivatives not designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	21,776	25,939
Derivatives not designated as hedging instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	22,225	25,968
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	21,776	25,939
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	22,044	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	181	157
Derivatives designated as hedging instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	123	5
Derivatives designated as hedging instruments | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	36	158
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	122	4
Derivatives designated as hedging instruments | Foreign exchange contracts | Other Liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	1	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	$ 35	$ 42