Reserves for Credit Losses - Changes in Loan Reserve (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provisions for credit losses	$ 1,268	$ 1,198	$ 2,537	$ 2,253
Card Member Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	5,271	4,053	5,118	3,747
Provisions for credit losses	970	923	1,984	1,709
Other	(7)	11	(13)	17
Ending Balance	5,321	4,390	5,321	4,390
Card Member Loans \| Principal
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Net write-offs	(753)	(490)	(1,458)	(887)
Recoveries	179	130	338	258
Card Member Loans \| Interest and fees
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Net write-offs	$ (160)	$ (107)	$ (310)	$ (196)

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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