Card Balances and Other Loans - Modifications (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Financing Receivable, Modifications [Line Items]
Maximum payment term extension			60 months
Unused credit available	$ 59	$ 59	$ 59	$ 59
Account Balances	1,075	1,035	2,795	2,616
Card Balances | Interest Rate Reduction | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	$ 605	$ 591	$ 1,566	$ 1,482
% of Total Class of Financing Receivables	0.50%	0.50%	1.30%	1.30%
Weighted Average Interest Rate Reduction (% points)	18.00%	18.20%	18.10%	18.30%
Card Balances | Interest Rate Reduction | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	$ 222	$ 221	$ 639	$ 582
% of Total Class of Financing Receivables	0.60%	0.70%	1.70%	1.70%
Weighted Average Interest Rate Reduction (% points)	18.10%	17.70%	18.10%	17.70%
Card Balances | 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 Balances | Term Extension | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	$ 94	$ 77	$ 199	$ 178
% of Total Class of Financing Receivables	0.40%	0.30%	0.80%	0.70%
Weighted Average Payment Term Extensions (# of months)	30 months	33 months	31 months	32 months
Card Balances | Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	$ 114	$ 111	$ 287	$ 287
% of Total Class of Financing Receivables	0.60%	0.60%	1.40%	1.50%
Weighted Average Payment Term Extensions (# of months)	30 months	30 months	31 months	30 months
Card Balances | Term Extension | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances	$ 9	$ 7	$ 19	$ 16
% of Total Class of Financing Receivables	0.10%	0.04%	0.10%	0.10%
Weighted Average Payment Term Extensions (# of months)	11 months	9 months	10 months	10 months
Other Loans | Interest Rate Reduction and Term Extension
Financing Receivable, Modifications [Line Items]
Account Balances	$ 22	$ 19	$ 57	$ 46
% of Total Class of Financing Receivables	0.20%	0.20%	0.50%	0.40%
Weighted Average Interest Rate Reduction (% points)	3.80%	3.40%	3.80%	3.30%
Weighted Average Payment Term Extensions (# of months)	21 months	21 months	21 months	21 months
Other Loans | Term Extension
Financing Receivable, Modifications [Line Items]
Account Balances	$ 9	$ 9	$ 29	$ 25
% of Total Class of Financing Receivables	0.10%	0.10%	0.20%	0.20%
Weighted Average Interest Rate Reduction (% points)	0.00%	0.00%	0.00%	0.00%
Weighted Average Payment Term Extensions (# of months)	19 months	16 months	18 months	17 months