CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Surplus	Accumulated Other Comprehensive Income (Loss)	Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment for adoption of new ASU | ASU 2014-09			$ (324)		$ (324)
BALANCE at Dec. 31, 2017	$ 114	$ 150,699	55,580	$ (3,293)	203,100
BALANCE at Dec. 31, 2017	114	150,699	55,256	(3,293)	202,776
Components of comprehensive income:
Net income			6,670		6,670
Foreign currency translation adjustments				817	817
COMPREHENSIVE INCOME			6,670	817	7,487
Issuance of common stock to non-employee directors		150			150
Dividends paid			(2,049)		(2,049)
BALANCE at Mar. 31, 2018	114	150,849	59,877	(2,476)	208,364
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment for adoption of new ASU | ASU 2016-02			4		4
BALANCE at Dec. 31, 2018	114	150,905	81,354	(4,810)	227,563
BALANCE at Dec. 31, 2018	114	150,905	81,358	(4,810)	227,567
Components of comprehensive income:
Net income			8,660		8,660
Foreign currency translation adjustments				277	277
COMPREHENSIVE INCOME			8,660	277	8,937
Issuance of common stock to non-employee directors		150			150
Dividends paid			(2,052)		(2,052)
BALANCE at Mar. 31, 2019	$ 114	$ 151,055	$ 87,966	$ (4,533)	$ 234,602