Derivative Financial Instruments - Schedule of The Fair Values of Derivative Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	$ 16,260	$ 15,214
Fair value of derivative liabilities	17,397	15,234
Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	16,116	15,135
Fair value of derivative liabilities	17,053	14,925
Interest-rate contracts
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	141	77
Fair value of derivative liabilities	232	239
Derivatives not designated as hedging instruments | Other assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	15,625	14,643
Derivatives not designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	17,177	15,008
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	15,610	14,626
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	17,053	14,922
Derivatives not designated as hedging instruments | Interest-rate contracts | Other assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	12	15
Derivatives not designated as hedging instruments | Interest-rate contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	12	16
Derivatives not designated as hedging instruments | Other derivative contracts | Other assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	3	2
Derivatives not designated as hedging instruments | Other derivative contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	112	70
Derivatives designated as hedging instruments | Other assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	635	571
Derivatives designated as hedging instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	220	226
Derivatives designated as hedging instruments | Foreign exchange contracts | Other assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	506	509
Derivatives designated as hedging instruments | Foreign exchange contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	0	3
Derivatives designated as hedging instruments | Interest-rate contracts | Other assets
Derivatives, Fair Value [Line Items]
Fair value of derivative assets	129	62
Derivatives designated as hedging instruments | Interest-rate contracts | Other liabilities
Derivatives, Fair Value [Line Items]
Fair value of derivative liabilities	$ 220	$ 223