Credit Quality and the Allowance for Loan and Lease Losses - Summary of Loans That Were Modified for Borrowers Experiencing Financial Difficulty (Details) - USD ($) $ in Millions	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	$ 460	$ 444
Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	415	435
30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	22	5
90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	23	4
Commercial | Commercial and industrial loans
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	210	191
Commercial | Commercial and industrial loans | Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	199	190
Commercial | Commercial and industrial loans | 30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	3	0
Commercial | Commercial and industrial loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	8	1
Commercial | Commercial mortgage owner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	34	40
Commercial | Commercial mortgage owner-occupied loans | Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	34	40
Commercial | Commercial mortgage owner-occupied loans | 30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	0	0
Commercial | Commercial mortgage owner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	0	0
Commercial | Commercial mortgage nonowner-occupied loans
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	50	26
Commercial | Commercial mortgage nonowner-occupied loans | Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	50	26
Commercial | Commercial mortgage nonowner-occupied loans | 30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	0	0
Commercial | Commercial mortgage nonowner-occupied loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	0	0
Commercial | Commercial construction loans
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	23	101
Commercial | Commercial construction loans | Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	23	101
Commercial | Commercial construction loans | 30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	0	0
Commercial | Commercial construction loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	0	0
Residential Mortgage
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	100	59
Residential Mortgage | Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	74	56
Residential Mortgage | 30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	15	2
Residential Mortgage | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	11	1
Consumer | Home equity
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	15	7
Consumer | Home equity | Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	13	7
Consumer | Home equity | 30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	1	0
Consumer | Home equity | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	1	0
Consumer | Credit card
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	23	17
Consumer | Credit card | Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	17	12
Consumer | Credit card | 30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	3	3
Consumer | Credit card | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	3	2
Consumer | Solar energy installation loans
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	1	1
Consumer | Solar energy installation loans | Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	1	1
Consumer | Solar energy installation loans | 30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	0	0
Consumer | Solar energy installation loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	0	0
Consumer | Other consumer loans
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	4	2
Consumer | Other consumer loans | Current
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	4	2
Consumer | Other consumer loans | 30-89 days past due
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	0	0
Consumer | Other consumer loans | 90 Days or More
Financing Receivable, Recorded Investment, Past Due
Financing receivable, excluding accrued interest, modified, after 12 months	$ 0	$ 0