QUARTERLY CONSOLIDATED FINANCIAL DATA (UNAUDITED) (Schedule of Quarterly Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 108,947	$ 124,571	$ 149,823	$ 162,110	$ 90,246	$ 104,877	$ 130,261	$ 137,225	$ 545,451	$ 462,609	$ 403,083
Gross margin	57,347	66,877	80,681	83,552	45,853	53,128	67,691	71,356	288,457	238,028
Net income	$ 8,850	$ 7,949	$ 16,118	$ 2,552	$ 3,806	$ 7,309	$ 12,085	$ 2,943	$ 35,469	$ 26,143	$ 19,311
Basic income per common share	$ 0.30	$ 0.27	$ 0.55	$ 0.09	$ 0.13	$ 0.25	$ 0.42	$ 0.10	$ 1.20	$ 0.90	$ 0.67
Diluted income per common share	$ 0.29	$ 0.27	$ 0.54	$ 0.09	$ 0.13	$ 0.25	$ 0.41	$ 0.10	$ 1.19	$ 0.89	$ 0.66