Loans and Allowance for Credit Losses - Loan Modifications by Delinquency Status (Details) - USD ($) $ in Millions	Jun. 30, 2025	Jun. 30, 2024
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	$ 3,588	$ 4,168
Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	3,200	3,475
30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	120	104
90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	268	589
Commercial | Commercial
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	702	762
Commercial | Commercial | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	556	628
Commercial | Commercial | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	38	17
Commercial | Commercial | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	108	117
Commercial | Commercial real estate
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	910	1,266
Commercial | Commercial real estate | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	799	847
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	111	419
Consumer | Residential mortgages
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	1,446	1,604
Consumer | Residential mortgages | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	1,433	1,585
Consumer | Residential mortgages | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	5	6
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	413	462
Consumer | Residential mortgages | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	8	13
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	239	196
Consumer | Credit card
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	415	391
Consumer | Credit card | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	316	293
Consumer | Credit card | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	64	64
Consumer | Credit card | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	35	34
Consumer | Other retail
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	115	145
Consumer | Other retail | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	96	122
Consumer | Other retail | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	13	17
Consumer | Other retail | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	$ 6	$ 6