Short-Term and Other Borrowings - Summary of Federal Funds Purchased, Securities Sold Under Agreements to Repurchase and Other Short-term Borrowings (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Maximum indebtedness	$ 35,000,000	$ 50,000,000
Average balance	$ 543,000	$ 385,000
Average rate paid	(1.47%)	0.35%
Short Term Borrowings, FHLB advances [Member]
Short-term Debt [Line Items]
Maximum indebtedness		$ 102,700,000
Average balance		$ 10,888,000
Average rate paid		1.64%