Parent Company Only Financial Information - Schedule of Condensed Statement of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net Earnings	$ 2,817	$ 2,220
Adjustments to reconcile net earnings to net cash used in operating activities:
Stock issued as compensation	15	1
Net decrease in other assets	(150)	198
Cash flows from financing activities:
Proceeds from sale of common stock	16,957
Proceeds from stock options exercised	195	261
Cash flows from investment activities:
Net (decrease) increase in cash and cash equivalents	(3,768)	27,736
Cash and cash equivalents at beginning of year	36,165	8,429
Cash and cash equivalents at end of year	32,397	36,165
Supplemental disclosure of cash flow information- Noncash items:
Net change in accumulated other comprehensive loss of subsidiary, net of change in unrealized loss on securities available for sale, net of tax	(18)	(289)
Parent Company [Member]
Cash flows from operating activities:
Net Earnings	2,817	2,220
Adjustments to reconcile net earnings to net cash used in operating activities:
Equity in earnings of subsidiary	(3,092)	(2,482)
Stock issued as compensation	65	55
Net decrease in other assets		207
Net cash used in operating activities	(210)
Cash flows from financing activities:
Proceeds from sale of common stock	16,957
Proceeds from stock options exercised	195	261
Net cash provided by financing activities	17,152	261
Cash flows from investment activities:
Cash dividend paid	(140)	(99)
Cash infusion to subsidiary	(4,000)
Net cash used by investing activities	(4,140)	(99)
Net (decrease) increase in cash and cash equivalents	12,802	162
Cash and cash equivalents at beginning of year	1,301	1,139
Cash and cash equivalents at end of year	14,103	1,301
Supplemental disclosure of cash flow information- Noncash items:
Net change in accumulated other comprehensive loss of subsidiary, net of change in unrealized loss on securities available for sale, net of tax	(18)	(289)
Stock-based compensation expense of subsidiary	$ 15	$ 1