Summary of Significant Accounting Policies Textuals (Details) $ in Millions				1 Months Ended	3 Months Ended	12 Months Ended
		Feb. 01, 2020 USD ($)	Jan. 01, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Apr. 20, 2020 USD ($)	Dec. 31, 2019 USD ($)		Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Accounting Policies [Abstract]
Ratio of combined earnings and fixed earnings to fixed charges required to maintain availability of credit line						1.25
Summary Of Significant Accounting Policies [Line Items]
Shareholders' equity						$ (2,895)		$ (2,587)		$ (2,196)	$ (1,871)
Removal of financing receivables (U.S. consumer Card Member receivables)					$ 7,200
Reduction in long term debt to affiliate		$ 7,200
Retained Earnings [Member]
Summary Of Significant Accounting Policies [Line Items]
Shareholders' equity						(3,833)		(3,513)		(3,095)	(2,708)
Restructuring of Loan Arrangements [Member] | Affiliated Entity [Member]
Summary Of Significant Accounting Policies [Line Items]
Amount borrowed from related party				$ 7,100
Repayment of borrowings from related party				4,700
Excess deposited with AENB				$ 2,200		500
Cumulative Effect, Period of Adoption, Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Current and deferred tax impact			$ 21
Shareholders' equity	[1]							(119)
Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained Earnings [Member]
Summary Of Significant Accounting Policies [Line Items]
Shareholders' equity			(119)					(119)	[1]
Card Member Loans [Member]
Summary Of Significant Accounting Policies [Line Items]
Receivable reserves						(20)		(10)		(5)	(5)
Card Member Loans [Member] | Global Consumer Services Group [Member]
Summary Of Significant Accounting Policies [Line Items]
Receivable reserves						(20)		(10)
Card Member Loans [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Decrease in financing receivable, allowance			(7)
Receivable reserves								(17)
Card Member Receivables [Member]
Summary Of Significant Accounting Policies [Line Items]
Receivable reserves						$ (70)		(162)		$ (167)	$ (145)
Removal of financing receivables (U.S. consumer Card Member receivables)		7,200
Card Member Receivables [Member] | Global Corporate Payments [Member]
Summary Of Significant Accounting Policies [Line Items]
Transfer of financing receivables		5,200					$ 1,700
Card Member Receivables [Member] | Global Consumer Services Group [Member]
Summary Of Significant Accounting Policies [Line Items]
Removal of financing receivables (U.S. consumer Card Member receivables)		$ 7,200
Card Member Receivables [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Decrease in financing receivable, allowance			$ 147
Receivable reserves								$ (15)

[1] Represents $140 million, net of tax of $21 million, related to the impact as of January 1, 2020, of adopting the new accounting guidance for the recognition of credit losses on certain financial instruments.