Loans and Card Member Receivables - Modifications (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Financing Receivable, Modifications [Line Items]
Maximum payment term extension			60 months
Unused credit available	$ 38	$ 50	$ 38	$ 50
Account Balances	946	971	1,837	1,944
Card Member Loans | Interest Rate Reduction | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	$ 520	$ 513	$ 1,005	$ 1,039
% of Total Class of Financing Receivables	0.50%	0.50%	0.90%	1.00%
Weighted Average Interest Rate Reduction (% points)	18.30%	18.20%	18.30%	18.10%
Card Member Loans | Interest Rate Reduction | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	$ 205	$ 185	$ 409	$ 370
% of Total Class of Financing Receivables	0.60%	0.60%	1.20%	1.20%
Weighted Average Interest Rate Reduction (% points)	17.70%	17.50%	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	$ 69	$ 92	$ 130	$ 184
% of Total Class of Financing Receivables	0.30%	0.40%	0.50%	0.80%
Weighted Average Payment Term Extensions (# of months)	31 months	30 months	31 months	29 months
Card Member Receivables | Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	$ 114	$ 142	$ 225	$ 283
% of Total Class of Financing Receivables	0.60%	0.70%	1.20%	1.50%
Weighted Average Payment Term Extensions (# of months)	30 months	29 months	30 months	29 months
Card Member Receivables | Term Extension | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances	$ 12	$ 9	$ 16	$ 12
% of Total Class of Financing Receivables	0.10%	0.10%	0.10%	0.10%
Weighted Average Payment Term Extensions (# of months)	10 months	9 months	10 months	9 months
Other Loans | Interest Rate Reduction and Term Extension
Financing Receivable, Modifications [Line Items]
Account Balances	$ 17	$ 18	$ 32	$ 34
% of Total Class of Financing Receivables	0.20%	0.20%	0.30%	0.40%
Weighted Average Interest Rate Reduction (% points)	3.30%	2.50%	3.20%	2.40%
Weighted Average Payment Term Extensions (# of months)	21 months	19 months	21 months	19 months
Other Loans | Term Extension
Financing Receivable, Modifications [Line Items]
Account Balances	$ 9	$ 12	$ 20	$ 22
% 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)	17 months	18 months	17 months	19 months