CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Total
Balance at Dec. 31, 2014	$ 191	$ 22,985	$ 186,745	$ (32,970)	$ 176,951
Balance (in shares) at Dec. 31, 2014	16,812,794
Increase (Decrease) in Stockholders' Equity
Net exercise of stock options		(2,666)		6,566	3,900
Net exercise of stock options (in shares)	389,905
Excess tax benefit from stock-based compensation		865			865
Stock based compensation expense		1,544			1,544
Net income			20,659		20,659
Balance at Dec. 31, 2015	$ 191	22,728	207,404	(26,404)	203,919
Balance (in shares) at Dec. 31, 2015	17,202,699
Increase (Decrease) in Stockholders' Equity
Net exercise of stock options		(1,312)		4,246	2,934
Net exercise of stock options (in shares)	265,570
Excess tax benefit from stock-based compensation		737			737
Stock based compensation expense		1,681			1,681
Net income			24,574		24,574
Balance at Dec. 31, 2016	$ 191	23,834	231,978	(22,158)	$ 233,845
Balance (in shares) at Dec. 31, 2016	17,468,269				17,468,269
Increase (Decrease) in Stockholders' Equity
Net exercise of stock options		812		4,035	$ 4,847
Net exercise of stock options (in shares)	291,177
Stock based compensation expense		2,244			2,244
Net income			25,538		25,538
Balance at Dec. 31, 2017	$ 191	$ 26,890	$ 257,516	$ (18,123)	$ 266,474
Balance (in shares) at Dec. 31, 2017	17,759,446				17,759,446