Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Retained Earnings [Member]
Beginning balance at Dec. 31, 2016	$ 69,693	$ 72	$ 9,638	$ (3)	$ 59,986
Beginning balance, shares at Dec. 31, 2016		7,244
Common stock issued on exercise of options and vesting of restricted stock units	98	$ 1	97
Common stock issued on exercise of options and vesting of restricted stock units, shares		9
Common stock repurchased on vesting of restricted stock units	(68)		(68)
Common stock repurchased on vesting of restricted stock units, shares		(1)
Share-based compensation expense	882		882
Cash dividends on common stock	(1,813)				(1,813)
Unrealized loss on investments, net of tax	(20)			(20)
Net loss	(11,227)				(11,227)
Ending balance at Mar. 31, 2017	57,545	$ 73	10,549	(23)	46,946
Ending balance, shares at Mar. 31, 2017		7,252
Beginning balance at Dec. 31, 2017	88,834	$ 73	12,311	(1,430)	77,880
Beginning balance, shares at Dec. 31, 2017		7,301
Common stock issued on exercise of options and vesting of restricted stock units	53		53
Common stock issued on exercise of options and vesting of restricted stock units, shares		7
Common stock repurchased on vesting of restricted stock units	(76)		(76)
Common stock repurchased on vesting of restricted stock units, shares		(1)
Share-based compensation expense	1,542		1,542
Cash dividends on common stock	(1,826)				(1,826)
Unrealized loss on investments, net of tax	(3,964)			(3,964)
Net loss	(9,123)				(9,123)
Ending balance at Mar. 31, 2018	$ 75,440	$ 73	$ 13,830	$ (5,394)	$ 66,931
Ending balance, shares at Mar. 31, 2018		7,307