Allowance for Loan Losses - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Percentage of loans granted forbearance that migrated to TDR classification	75.00%	75.00%
Payment default period for TDRs	60 days past due
Interest Rate Reduction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
TDR loans, Unpaid Principal Balance	$ 838	$ 831