Condensed Parent Company Only Financial Information - Condensed Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income (loss)	$ 2,758	$ 167	$ (4,592)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Income (loss) from other investments	(42)	51	218
Net cash provided by operating activities	4,957	3,144	4,639
Cash flows from investing activities:
Net cash provided by investing activities	20,266	(43,581)	27,713
Cash flows from financing activities:
Retirement of common stock	(502)
Dividends paid	(51)
Net cash provided by (used in) financing activities	(41,058)	50,157	(24,512)
Net increase (decrease) in cash	(15,835)	9,720	7,840
Cash and cash equivalents, beginning of year	41,116	31,396	23,556
Cash and cash equivalents, end of year	25,281	41,116	31,396
Parent Company [Member]
Cash flows from operating activities:
Net income (loss)	2,758	167	(4,592)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Income (loss) from other investments	(42)	51	218
Undistributed (income) loss of subsidiaries	(1,592)	(247)	4,242
Other assets	(20)	(8)
Net cash provided by operating activities	1,104	(37)	(132)
Cash flows from investing activities:
Redemption of equity securities		200
Net cash provided by investing activities		200
Cash flows from financing activities:
Retirement of common stock	(502)
Dividends paid	(51)
Net cash provided by (used in) financing activities	(553)
Net increase (decrease) in cash	551	163	(132)
Cash and cash equivalents, beginning of year	191	28	160
Cash and cash equivalents, end of year	$ 742	$ 191	$ 28