Transactions with Affiliates (Details Textuals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Parties Textuals [Abstract]
Card Member receivables and loans purchased without recourse from TRS	$ 262,000	$ 225,000	$ 227,000
Participation Interest And Card Member Receivables Sold To Affiliates	9,400	5,700	2,600
Discount Revenue Earned From Purchased Cardmember Receivables And Loans	760	471	479
Uncharged Servicing Fees to Affiliates	234	253	242
Restricted Cash with Affiliates	100	0	0
Long Term Debt with Affiliates	270	0	0
Related Party Transaction [Line Items]
Loans to affiliates and other	14,527	10,659	$ 14,262
Participation interests in Card Member receivables purchased without recourse	4,100	4,000
30 Days or More Past Due [Member] | Reserves for Losses [Member]
Related Party Transaction [Line Items]
Loans to affiliates and other	0	0
Collateralized [Member]
Related Party Transaction [Line Items]
Loans to affiliates and other	$ 5,000	$ 3,300