Quarterly Consolidated Financial Data (unaudited) - Schedule of Consolidated Quarterly Financial Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Consolidated Financial Data Unaudited [Abstract]
Revenues	$ 60,081	$ 66,920	$ 67,418	$ 60,679	$ 54,076	$ 61,641	$ 62,701	$ 54,362	$ 255,098	$ 232,780	$ 221,690
Gross profit	32,126	35,145	35,456	31,868	27,864	32,449	34,193	29,045	134,595	123,551	119,406
Income before income taxes	11,780	25,663	12,752	9,607	6,744	12,970	10,593	19,561	59,802	49,868	26,812
Net income	$ (804)	$ 17,369	$ 9,193	$ 7,151	$ 6,126	$ 9,286	$ 7,601	$ 13,939	$ 32,909	$ 36,952	$ 17,956
Income (loss) per share:
Basic	$ (0.03)	$ 0.55	$ 0.29	$ 0.23	$ 0.20	$ 0.30	$ 0.25	$ 0.45	$ 1.05	$ 1.19	$ 0.57
Diluted	$ (0.03)	$ 0.54	$ 0.29	$ 0.22	$ 0.19	$ 0.30	$ 0.24	$ 0.44	$ 1.02	$ 1.16	$ 0.56
Weighted average number of shares outstanding:
Basic	31,597	31,571	31,501	31,290	31,085	30,988	30,779	30,957	31,491	31,128	31,408
Diluted	31,597	32,170	32,146	32,058	32,018	31,459	31,754	31,654	32,162	31,790	32,166