Card Balances and Other Loans - Performance (Details) - USD ($) $ in Millions	Jun. 30, 2026	Jun. 30, 2025
Current
Financing Receivable, Modifications [Line Items]
Account balances	$ 3,105	$ 2,839
30-89 Days Past Due
Financing Receivable, Modifications [Line Items]
Account balances	201	205
90+ Days Past Due
Financing Receivable, Modifications [Line Items]
Account balances	82	82
Card Balances \| Current \| Consumer
Financing Receivable, Modifications [Line Items]
Account balances	1,971	1,810
Card Balances \| Current \| Small Business
Financing Receivable, Modifications [Line Items]
Account balances	1,023	939
Card Balances \| Current \| Corporate
Financing Receivable, Modifications [Line Items]
Account balances	17	12
Card Balances \| 30-89 Days Past Due \| Consumer
Financing Receivable, Modifications [Line Items]
Account balances	111	113
Card Balances \| 30-89 Days Past Due \| Small Business
Financing Receivable, Modifications [Line Items]
Account balances	83	84
Card Balances \| 30-89 Days Past Due \| Corporate
Financing Receivable, Modifications [Line Items]
Account balances	3	3
Card Balances \| 90+ Days Past Due \| Consumer
Financing Receivable, Modifications [Line Items]
Account balances	47	45
Card Balances \| 90+ Days Past Due \| Small Business
Financing Receivable, Modifications [Line Items]
Account balances	32	32
Card Balances \| 90+ Days Past Due \| Corporate
Financing Receivable, Modifications [Line Items]
Account balances	1	3
Other Loans \| Current
Financing Receivable, Modifications [Line Items]
Account balances	95	78
Other Loans \| 30-89 Days Past Due
Financing Receivable, Modifications [Line Items]
Account balances	5	5
Other Loans \| 90+ Days Past Due
Financing Receivable, Modifications [Line Items]
Account balances	$ 2	$ 2