Short-Term Borrowings - Summary of Short-Term Borrowings (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Short-term borrowings	$ 1,100	$ 1,100
Weighted average interest rate	0.30%	2.19%
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Short-term borrowings	$ 1,100	$ 1,100
Short-term Debt [Member]
Short-term Debt [Line Items]
End of period interest rate	0.05%	1.45%