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]	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
Other comprehensive income (loss)				671		671
Stock-based employee compensation expense			826			826
Issuance of restricted shares, net			(18)			(18)
Effect of adoption of ASU 2014-09					591	591
Balance at Mar. 31, 2018	171	24	138,050	964	162,479	301,688
Balance at Dec. 31, 2017	171	24	137,242	293	157,471	295,201
Net income						14,388
Balance at Jun. 30, 2018	171	24	139,362	1,544	172,450	313,551
Balance at Mar. 31, 2018	171	24	138,050	964	162,479	301,688
Net income					9,971	9,971
Other comprehensive income (loss)				580		580
Stock-based employee compensation expense			937			937
Issuance of restricted shares, net			375			375
Balance at Jun. 30, 2018	171	24	139,362	1,544	172,450	313,551
Balance at Dec. 31, 2018	171	24	142,177	204	200,566	343,142
Net income					4,433	4,433
Other comprehensive income (loss)				(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
Balance at Dec. 31, 2018	171	24	142,177	204	200,566	343,142
Net income						10,504
Balance at Jun. 30, 2019	172	24	141,337	(918)	211,070	351,685
Balance at Mar. 31, 2019	172	24	142,770	(228)	204,999	347,737
Net income					6,071	6,071
Other comprehensive income (loss)				(690)		(690)
Issuance of restricted shares, net
Stock-based employee compensation expense reversal			(1,433)			(1,433)
Balance at Jun. 30, 2019	$ 172	$ 24	$ 141,337	$ (918)	$ 211,070	$ 351,685