Revenue from Contracts with Customers (Schedule of Revenue from Contracts with Customers Disaggregated by Business Segment) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net		$ 237	$ 299	$ 453	$ 530
Protection products revenue		44	49	91	98
Transaction processing revenue		49	48	93	94
Other income subject to ASC 606		14	22	42	50
Loan fee income		85	102	204	206
Gains on equity investments		43	0	79	0
Total other income not subject to ASC 606		128	102	283	206
Total other income by operating segment		472	520	962	978
Customer rewards included in discount and interchange revenue		385	460	863	906
Deposit product fees reported in net interest income and excluded from other income subject to ASC 606		1	1	1	2
Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net	[1]	237	299	453	530
Protection products revenue		44	49	91	98
Transaction processing revenue		49	48	93	94
Other income subject to ASC 606		14	22	42	50
Total other income subject to ASC 606	[2]	344	418	679	772
Operating Segments [Member] | Direct Banking [Member]
Disaggregation of Revenue [Line Items]
Loan fee income		85	102	204	206
Gains on equity investments		0	0	0	0
Total other income not subject to ASC 606		85	102	204	206
Total other income by operating segment		354	436	720	808
Operating Segments [Member] | Direct Banking [Member] | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net	[1]	222	283	419	500
Protection products revenue		44	49	91	98
Transaction processing revenue		0	0	0	0
Other income subject to ASC 606		3	2	6	4
Total other income subject to ASC 606	[2]	269	334	516	602
Operating Segments [Member] | Payment Services [Member]
Disaggregation of Revenue [Line Items]
Loan fee income		0	0	0	0
Gains on equity investments		43	0	79	0
Total other income not subject to ASC 606		43	0	79	0
Total other income by operating segment		118	84	242	170
Operating Segments [Member] | Payment Services [Member] | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net	[1]	15	16	34	30
Protection products revenue		0	0	0	0
Transaction processing revenue		49	48	93	94
Other income subject to ASC 606		11	20	36	46
Total other income subject to ASC 606	[2]	$ 75	$ 84	$ 163	$ 170

[1] Net of rewards, including Cashback Bonus rewards, of $385 million and $460 million for the three months ended June 30, 2020 and 2019, respectively.

[2] Excludes $1 million and $1 million of deposit product fees that are reported within net interest income for the three months ended June 30, 2020 and 2019, respectively.