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, 2014	$ 262	$ 252,421	$ 34,660	$ 1,062		$ 288,405
BALANCE-beginning of period (in shares) at Dec. 31, 2014	26,176
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			12,866			12,866
Net change in unrealized gains and losses on available-for-sale securities, net of taxes and reclassification adjustment				308		308
Issuance of common stock in connection with the exercise of stock options	$ 1	954				955
Issuance of common stock in connection with the exercise of stock options (in shares)	101
Stock-based compensation expense		695				695
BALANCE-end of period at Sep. 30, 2015	$ 263	254,070	47,526	1,370		303,229
BALANCE-end of period (in shares) at Sep. 30, 2015	26,277
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			(3,516)			(3,516)
Net change in unrealized gains and losses on available-for-sale securities, net of taxes and reclassification adjustment				562		562
Issuance of common stock in connection with the exercise of stock options	$ 1	71				72
Issuance of common stock in connection with the exercise of stock options (in shares)	251
Purchase of treasury stock					$ (1,253)	(1,253)
Purchase of treasury stock (in shares)	(178)
Stock-based compensation expense		948				948
BALANCE-end of period at Sep. 30, 2016	$ 369	$ 379,537	$ 46,583	$ 979	$ (1,253)	$ 426,215
BALANCE-end of period (in shares) at Sep. 30, 2016	36,861