Loans and Allowance for Credit Losses - Loan Modifications by Delinquency Status (Details) - USD ($) $ in Millions	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	$ 4,168	$ 1,368
Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	3,475	1,191
30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	104	55
90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	589	122
Commercial | Commercial
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	762	318
Commercial | Commercial | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	628	287
Commercial | Commercial | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	17	7
Commercial | Commercial | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	117	24
Commercial | Commercial real estate
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	1,266	109
Commercial | Commercial real estate | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	847	43
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	419	66
Consumer | Residential mortgages
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	1,604	692
Consumer | Residential mortgages | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	1,585	668
Consumer | Residential mortgages | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	6	11
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	462	95
Consumer | Residential mortgages | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	13	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	196	20
Consumer | Credit card
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	391	174
Consumer | Credit card | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	293	125
Consumer | Credit card | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	64	34
Consumer | Credit card | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	34	15
Consumer | Other retail
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	145	75
Consumer | Other retail | Current
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	122	68
Consumer | Other retail | 30-89 Days Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	17	3
Consumer | Other retail | 90 Days or More Past Due
Financing Receivable, Modified [Line Items]
Loan balances modified during the prior 12 months	$ 6	$ 4