Loans and Allowance for Credit Losses - Loan Modifications by Delinquency Status (Details) - USD ($) $ in Millions	Jun. 30, 2026	Jun. 30, 2025
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	$ 3,364	$ 3,588
Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	2,907	3,200
30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	107	120
90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	350	268
Commercial \| Commercial
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	637	624
Commercial \| Commercial \| Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	503	504
Commercial \| Commercial \| 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	4	22
Commercial \| Commercial \| 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	130	98
Commercial \| Commercial real estate
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	1,076	910
Commercial \| Commercial real estate \| Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	917	799
Commercial \| Commercial real estate \| 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	0	0
Commercial \| Commercial real estate \| 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	159	111
Consumer \| Residential mortgages
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	1,025	1,446
Consumer \| Residential mortgages \| Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	1,009	1,433
Consumer \| Residential mortgages \| 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	6	5
Consumer \| Residential mortgages \| 30-89 Days Past Due \| Loans purchased from GNMA mortgage pools
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	186	413
Consumer \| Residential mortgages \| 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	10	8
Consumer \| Residential mortgages \| 90 Days or More Past Due \| Loans purchased from GNMA mortgage pools
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	218	239
Consumer \| Credit card
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	531	493
Consumer \| Credit card \| Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	400	368
Consumer \| Credit card \| 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	85	80
Consumer \| Credit card \| 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	46	45
Consumer \| Other retail
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	95	115
Consumer \| Other retail \| Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	78	96
Consumer \| Other retail \| 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	12	13
Consumer \| Other retail \| 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	$ 5	$ 6

Financing Receivable, Modified [Line Items]