Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member] Common Class A [Member]	Common Stock [Member] Common Class B [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2017	$ 171	$ 24	$ 137,242	$ 293	$ 157,471	$ 295,201
Net income					4,417	4,417	$ 4,417
Effect of adoption of ASU 2014-09					591	591
Other comprehensive income				671		671
Stock-based employee compensation expense			826			826
Issuance of restricted shares, net			(18)			(18)
Balance at Mar. 31, 2018	171	24	138,050	964	162,479	301,688
Balance at Dec. 31, 2018	171	24	142,177	204	200,566	343,142
Net income					4,433	4,433	$ 4,433
Other comprehensive income				(432)		(432)
Stock-based employee compensation expense			1,262			1,262
Issuance of restricted shares, net	1		(669)			(668)
Balance at Mar. 31, 2019	$ 172	$ 24	$ 142,770	$ (228)	$ 204,999	$ 347,737