Allowance for Loan Losses - ALL by Loan Type (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	$ 7,479	$ 7,113	$ 7,902	$ 7,770
Charge-offs	(554)	(472)	(1,531)	(1,379)
Recoveries	75	137	253	415
Provision (recovery of)	495	509	871	481
Ending Balance	7,495	7,287	7,495	7,287
Mortgage Loans on Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	5,052	4,244	4,967	3,864
Charge-offs	(209)	(54)	(368)	(168)
Recoveries	24	60	67	103
Provision (recovery of)	214	157	415	608
Ending Balance	5,081	4,407	5,081	4,407
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	1,537	944	1,374	878
Charge-offs				(116)
Recoveries	1		1	1
Provision (recovery of)	114	186	277	367
Ending Balance	1,652	1,130	1,652	1,130
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	890	1,925	1,561	3,028
Charge-offs	(345)	(418)	(1,163)	(1,095)
Recoveries	50	77	185	311
Provision (recovery of)	167	166	179	(494)
Ending Balance	$ 762	$ 1,750	$ 762	$ 1,750