Loans and Leases and the Allowance for Credit Losses - Loan Modification Activities to Borrowers Experiencing Financial Difficulty on Financing Receivables (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 638	$ 304
Percent of total loan class	0.47%	0.23%
Payment Deferral [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 634	$ 302
Combination of Modification Types [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	4	2
Commercial and Industrial [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 184	$ 70
Percent of total loan class	0.32%	0.13%
Commercial and Industrial [Member] | Payment Deferral [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 184	$ 70
Commercial Real Estate [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 270	$ 94
Percent of total loan class	1.07%	0.35%
Commercial Real Estate [Member] | Payment Deferral [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 267	$ 94
Commercial Real Estate [Member] | Combination of Modification Types [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	3
Residential Builder and Developer [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 2	$ 8
Percent of total loan class	0.18%	0.64%
Residential Builder and Developer [Member] | Payment Deferral [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 2	$ 8
Other Commercial Construction [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 131	$ 92
Percent of total loan class	2.11%	1.39%
Other Commercial Construction [Member] | Payment Deferral [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 131	$ 92
Residential [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 49	$ 35
Percent of total loan class	0.22%	0.15%
Residential [Member] | Payment Deferral [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 48	$ 33
Residential [Member] | Combination of Modification Types [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	1	2
Residential Limited Documentation [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 2	$ 5
Percent of total loan class	0.17%	0.51%
Residential Limited Documentation [Member] | Payment Deferral [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 2	$ 5