Allowance for Loan Losses - ALL by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	$ 7,923	$ 3,993	$ 7,770	$ 3,863
(Charge-offs)	(519)	(334)	(907)	(474)
Recoveries	57	14	278	94
Provision (recovery)	(348)	568	(28)	758
Ending Balance	7,113	4,241	7,113	4,241
Mortgage Loans on Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	4,190	3,421	3,864	3,318
(Charge-offs)	(83)	(141)	(114)	(273)
Recoveries	16	10	43	88
Provision (recovery)	121	396	451	553
Ending Balance	4,244	3,686	4,244	3,686
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	1,043	528	878	493
(Charge-offs)	(101)		(116)
Recoveries		1		1
Provision (recovery)	2	(73)	182	(38)
Ending Balance	944	456	944	456
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	2,690	44	3,028	52
(Charge-offs)	(335)	(193)	(677)	(201)
Recoveries	41	3	235	5
Provision (recovery)	(471)	245	(661)	243
Ending Balance	$ 1,925	$ 99	$ 1,925	$ 99