CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
NET REVENUES		$ 103,081	$ 104,688
COST OF REVENUES		49,537	54,212
GROSS PROFIT		53,544	50,476
OPERATING EXPENSES:
Research and development		17,481	16,640
Sales and marketing		13,088	12,216
General and administrative		9,014	8,704
Total operating expenses		39,583	37,560
INCOME FROM OPERATIONS		13,961	12,916
OTHER INCOME		836	506
INCOME BEFORE INCOME TAXES		14,797	13,422
PROVISION FOR (BENEFIT FROM) INCOME TAXES		597	(677)
NET INCOME		$ 14,200	$ 14,099
EARNINGS PER SHARE:
Basic (in dollars per share)		$ 0.48	$ 0.48
Diluted (in dollars per share)	[1]	$ 0.46	$ 0.47
SHARES USED IN PER SHARE CALCULATION:
Basic (in shares)		29,799	29,456
Diluted (in shares)		30,552	30,248

[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.