CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
NET REVENUES		$ 109,482	$ 107,563	$ 212,563	$ 212,251
COST OF REVENUES		53,248	54,116	102,785	108,328
GROSS PROFIT		56,234	53,447	109,778	103,923
OPERATING EXPENSES:
Research and development		17,898	17,341	35,379	33,981
Sales and marketing		13,497	13,144	26,585	25,360
General and administrative		9,220	8,765	18,234	17,469
Total operating expenses		40,615	39,250	80,198	76,810
INCOME FROM OPERATIONS		15,619	14,197	29,580	27,113
OTHER INCOME		885	465	1,721	971
INCOME BEFORE INCOME TAXES		16,504	14,662	31,301	28,084
PROVISION FOR INCOME TAXES		1,123	760	1,720	83
NET INCOME		$ 15,381	$ 13,902	$ 29,581	$ 28,001
EARNINGS PER SHARE:
Basic (in dollars per share)		$ 0.52	$ 0.47	$ 1.00	$ 0.95
Diluted (in dollars per share)	[1]	$ 0.51	$ 0.46	$ 0.97	$ 0.92
SHARES USED IN PER SHARE CALCULATION:
Basic (in shares)		29,505	29,720	29,651	29,589
Diluted (in shares)		30,183	30,454	30,387	30,370

[1] The Company includes the shares underlying performance-based awards in the calculation of diluted earnings per share if the performance conditions have been satisfied as of the end of the reporting period and excludes such shares when the necessary conditions have not been met. The Company has excluded the shares underlying the outstanding performance-based awards in the 2018 and 2017 calculations as the shares were not contingently issuable as of the end of the reporting periods.