Loans and Leases and the Allowance for Credit Losses - Summary of Payment Status of Loans Modified (Detail) $ in Millions	Mar. 31, 2024 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 1,693
30-89 Days Past Due	121
Past Due 90 Days or More	64
Total	1,878
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	310
30-89 Days Past Due	7
Past Due 90 Days or More	10
Total	327
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	715
30-89 Days Past Due	33
Past Due 90 Days or More	24
Total	772
Residential Builder and Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	14
30-89 Days Past Due	39
Total	53
Other Commercial Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	534
30-89 Days Past Due	5
Total	539
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	112
30-89 Days Past Due	35
Past Due 90 Days or More	30
Total	177
Residential Limited Documentation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	6
30-89 Days Past Due	2
Total	8
Home Equity Lines and Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	2
Total	$ 2