Derivatives and Hedging Activities (Details 2) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gains (losses)	$ 44	$ (48)	$ (1)	$ 86
Other Expense [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gains (losses)	0	0	0	83
Other Expense [Member] | Foreign exchange contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gains (losses)	40	(50)	(4)	0
Cost Of Card Member Services [Member] | Foreign exchange contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Pretax gains (losses)	$ 4	$ 2	$ 3	$ 3