Loans - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Receivables [Abstract]
Net deferred origination costs (fees)	$ 57	$ 79
Net unamortized premium (discount)	$ 9	$ 3
Executive Officers and Directors [Member]
Related Party Transaction [Line Items]
Loans outstanding to executive officers and director as percent of shareholders equity, maximum (percent)	5.00%	5.00%