Loans and Card Member Receivables - Modifications (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Financing Receivable, Modifications [Line Items]
Maximum payment term extension			60 months
Unused credit available	$ 59	$ 70	$ 59	$ 70
Account Balances	1,035	956	2,616	2,630
Card Member Loans | Interest Rate Reduction | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	$ 591	$ 511	$ 1,482	$ 1,438
% of Total Class of Financing Receivables	0.50%	0.50%	1.30%	1.40%
Weighted Average Interest Rate Reduction (% points)	18.20%	18.30%	18.30%	18.20%
Card Member Loans | Interest Rate Reduction | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	$ 221	$ 185	$ 582	$ 514
% of Total Class of Financing Receivables	0.70%	0.60%	1.70%	1.60%
Weighted Average Interest Rate Reduction (% points)	17.70%	17.60%	17.70%	17.50%
Card Member Loans | Interest Rate Reduction | Corporate
Financing Receivable, Modifications [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, Modifications [Line Items]
Account Balances	$ 77	$ 89	$ 178	$ 232
% of Total Class of Financing Receivables	0.30%	0.40%	0.70%	1.00%
Weighted Average Payment Term Extensions (# of months)	33 months	31 months	32 months	30 months
Card Member Receivables | Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	$ 111	$ 138	$ 287	$ 359
% of Total Class of Financing Receivables	0.60%	0.70%	1.50%	1.90%
Weighted Average Payment Term Extensions (# of months)	30 months	31 months	30 months	30 months
Card Member Receivables | Term Extension | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances	$ 7	$ 9	$ 16	$ 15
% of Total Class of Financing Receivables	0.04%	0.10%	0.10%	0.10%
Weighted Average Payment Term Extensions (# of months)	9 months	10 months	10 months	9 months
Other Loans | Interest Rate Reduction and Term Extension
Financing Receivable, Modifications [Line Items]
Account Balances	$ 19	$ 16	$ 46	$ 46
% of Total Class of Financing Receivables	0.20%	0.20%	0.40%	0.50%
Weighted Average Interest Rate Reduction (% points)	3.40%	2.50%	3.30%	2.50%
Weighted Average Payment Term Extensions (# of months)	21 months	20 months	21 months	20 months
Other Loans | Term Extension
Financing Receivable, Modifications [Line Items]
Account Balances	$ 9	$ 8	$ 25	$ 26
% of Total Class of Financing Receivables	0.10%	0.10%	0.20%	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	16 months	17 months	18 months