Derivatives and Hedging Activities (Details Textuals) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Margin on interest rate swap not netted	$ 34,000,000	$ 47,000,000
Carrying value of derivative liabilities	588,000,000	341,000,000
Net increases (reductions) in interest expense on long term debt and other	(256,000,000)	102,000,000	$ 51,000,000
Net gains (losses) related to hedges of investment in foreign operations	(252,000,000)	(140,000,000)
Income associated with the sale or liquidation of a business	1,000,000	0	1,000,000
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Carrying value of derivative liabilities	16,400,000,000	22,700,000,000
Card Member Services Expense [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) in changes of fair value of derivatives not designated as hedges	10,000,000	64,000,000	60,000,000
Gain on embedded derivatives	0	3,000,000
Loss on embedded derivatives			11,000,000
Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Fixed-rate debt obligations designated in fair value relationships	15,800,000,000	22,600,000,000
Cumulative amount of fair value hedging adjustments	622,000,000	217,000,000
Net Investment Hedges [Member]
Derivatives, Fair Value [Line Items]
Notional amounts of foreign currency derivatives	10,500,000,000	9,800,000,000
Net gains (losses) related to hedges of investment in foreign operations	(252,000,000)	(140,000,000)	$ 328,000,000
Credit Valuation Adjustment [Member]
Derivatives, Fair Value [Line Items]
Fixed-rate debt obligations designated in fair value relationships	$ 0	$ 0