Transactions with Affiliates Textuals (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Related Party Transactions [Abstract]
Card Member receivables and loans purchased without recourse from TRS		$ 165,000,000,000	$ 316,000,000,000	$ 299,000,000,000
Participation interest and card member receivables sold to affiliates		12,700,000,000	1,100,000,000	6,200,000,000
Discount revenue earned from purchased Card Member receivables and Card Member loans		584,000,000	1,204,000,000	1,017,000,000
Participation interests in card member receivables purchased		4,200,000,000	8,100,000,000
Related Party Transaction [Line Items]
Loans to affiliates and other		10,890,000,000	10,345,000,000	14,136,000,000
Restricted cash with affiliates		120,000,000	116,000,000	93,000,000
Uncharged servicing fees to affiliates		250,000,000	328,000,000	$ 305,000,000
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Loss reserves		0	0
Collateralized [Member]
Related Party Transaction [Line Items]
Loans to affiliates and other		6,400,000,000	$ 8,200,000,000
Restructuring of Loan Arrangements [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Amount borrowed from related party	$ 7,100,000,000
Repayment of borrowings from related party	4,700,000,000
Excess deposited with AENB	$ 2,200,000,000	$ 500,000,000