Consolidated Statement of Changes in Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Total
BALANCE-beginning of period at Dec. 31, 2015	$ 368	$ 378,518	$ 50,099	$ 417		$ 429,402
BALANCE-beginning of period (in shares) at Dec. 31, 2015	36,788
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			1,839			1,839
Net change in unrealized gains and losses on available-for-sale securities, net of taxes and reclassification adjustment				595		595
Purchase of treasury stock					$ (1,253)	(1,253)
Stock-based compensation expense		327				327
BALANCE-end of period at Mar. 31, 2016	$ 368	378,845	51,938	1,012	(1,253)	430,910
BALANCE-end of period (in shares) at Mar. 31, 2016	36,788
BALANCE-beginning of period at Dec. 31, 2016	$ 372	382,961	49,127	(725)	(1,253)	430,482
BALANCE-beginning of period (in shares) at Dec. 31, 2016	36,988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			7,212			7,212
Net change in unrealized gains and losses on available-for-sale securities, net of taxes and reclassification adjustment				(1,024)		(1,024)
Issuance of common stock in connection with the exercise of stock options		271				271
Issuance of common stock in connection with the exercise of stock options (in shares)	205
Stock-based compensation expense		347				347
BALANCE-end of period at Mar. 31, 2017	$ 372	$ 383,579	$ 56,339	$ (1,749)	$ (1,253)	$ 437,288
BALANCE-end of period (in shares) at Mar. 31, 2017	37,193