Allowance for Loan Losses - ALL by Loan Type (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	$ 7,902	$ 7,770
Charge-offs	(461)	(388)
Recoveries	103	221
Provision (recovery of)	314	320
Ending Balance	7,858	7,923
Mortgage Loans on Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	4,967	3,864
Charge-offs	(54)	(31)
Recoveries	24	27
Provision (recovery of)	322	330
Ending Balance	5,259	4,190
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	1,374	878
Charge-offs		(14)
Recoveries	1
Provision (recovery of)	31	179
Ending Balance	1,406	1,043
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	1,561	3,028
Charge-offs	(407)	(343)
Recoveries	78	194
Provision (recovery of)	(39)	(189)
Ending Balance	$ 1,193	$ 2,690