CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
NET REVENUES		$ 415,955	$ 431,755	$ 389,668
COST OF REVENUES		201,167	218,091	197,477
GROSS PROFIT		214,788	213,664	192,191
OPERATING EXPENSES:
Research and development		70,580	68,501	62,310
Sales and marketing		53,064	51,384	47,978
General and administrative		35,496	36,142	33,029
Total operating expenses		159,140	156,027	143,317
INCOME FROM OPERATIONS		55,648	57,637	48,874
OTHER INCOME		4,116	2,662	1,078
INCOME BEFORE INCOME TAXES		59,764	60,299	49,952
PROVISION (BENEFIT) FOR INCOME TAXES		(10,220)	32,690	1,054
NET INCOME		$ 69,984	$ 27,609	$ 48,898
EARNINGS PER SHARE:
Basic		$ 2.38	$ 0.93	$ 1.69
Diluted	[1]	$ 2.32	$ 0.90	$ 1.65
SHARES USED IN PER SHARE CALCULATION:
Basic		29,456	29,674	28,925
Diluted	[1]	30,147	30,545	29,619

[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 included in the 2018, 2017 and 2016 calculations those shares that were contingently issuable upon the satisfaction of the performance conditions as of the end of the respective periods.