Allowance for Loan Losses - ALL by Loan Type (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	$ 7,858	$ 7,923	$ 7,902	$ 7,770
Charge-offs	(516)	(519)	(978)	(907)
Recoveries	75	57	179	278
Provision (recovery of)	62	(348)	376	(28)
Ending Balance	7,479	7,113	7,479	7,113
Mortgage Loans on Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	5,259	4,190	4,967	3,864
Charge-offs	(105)	(83)	(159)	(114)
Recoveries	18	16	43	43
Provision (recovery of)	(120)	121	201	451
Ending Balance	5,052	4,244	5,052	4,244
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	1,406	1,043	1,374	878
Charge-offs		(101)		(116)
Recoveries			1
Provision (recovery of)	131	2	162	182
Ending Balance	1,537	944	1,537	944
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	1,193	2,690	1,561	3,028
Charge-offs	(411)	(335)	(819)	(677)
Recoveries	57	41	135	235
Provision (recovery of)	51	(471)	13	(661)
Ending Balance	$ 890	$ 1,925	$ 890	$ 1,925