Loans and Leases and the Allowance for Credit Losses - Loan Modification Activities to Borrowers Experiencing Financial Difficulty on Financing Receivables (Parenthetical) (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
Guaranteed by Government-Related Entities [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	44	23
Unfunded Commitments to Extend Credit [Member]
Financing Receivable, Modifications other than Troubled Debt Restructuring [Line Items]
Financing receivable, modifications other than troubled debt restructuring	$ 29	$ 11