Asset Quality - Schedule of Performance of Loans That Have Been Modified in the Last 12 Months (Details) - USD ($) $ in Millions	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	$ 247	$ 190
Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	201	177
30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	40	5
90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	6	8
Total commercial loans
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	218	175
Total commercial loans | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	175	163
Total commercial loans | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	38	5
Total commercial loans | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	5	7
Total commercial loans | Commercial and Industrial
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	146	168
Total commercial loans | Commercial and Industrial | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	134	156
Total commercial loans | Commercial and Industrial | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	10	5
Total commercial loans | Commercial and Industrial | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	2	7
Total commercial loans | Total commercial real estate loans
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	218	175
Total commercial loans | Total commercial real estate loans | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	175	163
Total commercial loans | Total commercial real estate loans | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	38	5
Total commercial loans | Total commercial real estate loans | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	5	7
Total commercial loans | Commercial mortgage
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	42	7
Total commercial loans | Commercial mortgage | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	11	7
Total commercial loans | Commercial mortgage | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	28	0
Total commercial loans | Commercial mortgage | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	3	0
Total commercial loans | Construction
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	30	0
Total commercial loans | Construction | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	30	0
Total commercial loans | Construction | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	0
Total commercial loans | Construction | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	0
Total commercial loans | Commercial lease financing
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	0
Total commercial loans | Commercial lease financing | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	0
Total commercial loans | Commercial lease financing | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	0
Total commercial loans | Commercial lease financing | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	0
Total consumer loans
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	29	15
Total consumer loans | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	26	14
Total consumer loans | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	2	0
Total consumer loans | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	1	1
Total consumer loans | Real estate — residential mortgage
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	10	6
Total consumer loans | Real estate — residential mortgage | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	10	5
Total consumer loans | Real estate — residential mortgage | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	0
Total consumer loans | Real estate — residential mortgage | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	1
Total consumer loans | Home equity loans
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	11	5
Total consumer loans | Home equity loans | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	9	5
Total consumer loans | Home equity loans | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	1	0
Total consumer loans | Home equity loans | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	1	0
Total consumer loans | Other consumer loans
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	4	2
Total consumer loans | Other consumer loans | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	3	2
Total consumer loans | Other consumer loans | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	1	0
Total consumer loans | Other consumer loans | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	0
Total consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	4	2
Total consumer loans | Credit cards | Current
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	4	2
Total consumer loans | Credit cards | 30-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	0	0
Total consumer loans | Credit cards | 90 and Greater Days Past Due
Financing Receivable, Past Due [Line Items]
Total loans modified in last 12 months	$ 0	$ 0