Loans and Card Member Receivables - Modifications (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Financing Receivable, Troubled Debt Restructuring [Line Items]
Maximum payment term extension			60 months
Unused credit available	$ 70	$ 48	$ 70	$ 48
Account Balances	956	1,044	2,630	2,320
Card Member Loans | Interest Rate Reduction | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 511	$ 542	$ 1,438	$ 1,113
% of Total Class of Financing Receivables	0.50%	0.60%	1.40%	1.20%
Weighted Average Interest Rate Reduction (% points)	18.30%	16.40%	18.20%	16.10%
Card Member Loans | Interest Rate Reduction | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 185	$ 167	$ 514	$ 411
% of Total Class of Financing Receivables	0.60%	0.60%	1.60%	1.50%
Weighted Average Interest Rate Reduction (% points)	17.60%	15.90%	17.50%	15.70%
Card Member Loans | Interest Rate Reduction | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 0	$ 0	$ 0	$ 0
% of Total Class of Financing Receivables	0.00%	0.00%	0.00%	0.00%
Weighted Average Interest Rate Reduction (% points)	0.00%	0.00%	0.00%	0.00%
Card Member Receivables | Term Extension | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 89	$ 126	$ 232	$ 282
% of Total Class of Financing Receivables	0.40%	0.60%	1.00%	1.30%
Weighted Average Payment Term Extensions (# of months)	31 months	30 months	30 months	27 months
Card Member Receivables | Term Extension | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 138	$ 181	$ 359	$ 455
% of Total Class of Financing Receivables	0.70%	0.90%	1.90%	2.30%
Weighted Average Payment Term Extensions (# of months)	31 months	30 months	30 months	27 months
Card Member Receivables | Term Extension | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 9	$ 4	$ 15	$ 12
% of Total Class of Financing Receivables	0.10%	0.02%	0.10%	0.10%
Weighted Average Payment Term Extensions (# of months)	10 months	10 months	9 months	10 months
Other Loans | Interest Rate Reduction and Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 16	$ 16	$ 46	$ 28
% of Total Class of Financing Receivables	0.20%	0.20%	0.50%	0.40%
Weighted Average Interest Rate Reduction (% points)	2.50%	2.10%	2.50%	2.00%
Weighted Average Payment Term Extensions (# of months)	20 months	20 months	20 months	19 months
Other Loans | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 8	$ 8	$ 26	$ 19
% of Total Class of Financing Receivables	0.10%	0.10%	0.30%	0.30%
Weighted Average Interest Rate Reduction (% points)	0.00%	0.00%	0.00%	0.00%
Weighted Average Payment Term Extensions (# of months)	16 months	19 months	18 months	18 months