Loans and Allowance for Credit Losses - Loans modified by class and modification type (Detail) (Parenthetical) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 899
Payment Deferral And Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	52
Contractual Interest Rate Reduction And Extended Maturity [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	32
Contractual Interest Rate Reduction Extended Maturity And Payment Deferral [Member]
Financing Receivable, Modifications [Line Items]
Loans modified during the period	$ 5