Legal Proceedings (Narrative) (Details) $ in Millions	1 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)
Legal Reserve [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Loss contingency, range of possible loss not accrued	$ 125	$ 125
Interchange Litigation [Member]
Loss Contingencies [Line Items]
Additional legal settlement payment from all defendants	900
Settlement paid by defendants pursuant to the original 2012 settlement agreement		$ 5,300
Maximum return of legal payments to defendants if more than 15% of class members opt out of the class	$ 700
Percent of class members who must opt out to trigger return of a portion of the settlement paid (percent)	15.00%
Percent of class members who must opt out to allw termination of Amended Settlement Agreement Litigation Settlement, Trigger Percent of Opt Out by Class Members to Allow Termination of Amended Settlement Agreement	25.00%
Visa [Member] | Interchange Litigation [Member]
Loss Contingencies [Line Items]
Additional legal settlement payment from all defendants	$ 600
Maximum return of legal payments to defendants if more than 15% of class members opt out of the class	$ 467