CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
NET REVENUES		$ 431,755	$ 389,668	$ 344,609
COST OF REVENUES		218,091	197,477	171,309
GROSS PROFIT		213,664	192,191	173,300
OPERATING EXPENSES:
Research and development		68,501	62,310	57,549
Sales and marketing		51,384	47,978	46,816
General and administrative		36,142	33,029	30,029
Total operating expenses		156,027	143,317	134,394
INCOME FROM OPERATIONS		57,637	48,874	38,906
OTHER INCOME		2,662	1,078	425
INCOME BEFORE INCOME TAXES		60,299	49,952	39,331
PROVISION FOR INCOME TAXES		32,690	1,054	179
NET INCOME		$ 27,609	$ 48,898	$ 39,152
EARNINGS PER SHARE:
Basic		$ 0.93	$ 1.69	$ 1.35
Diluted	[1]	$ 0.90	$ 1.65	$ 1.32
SHARES USED IN PER SHARE CALCULATION:
Basic		29,674	28,925	29,001
Diluted	[1]	30,545	29,619	29,696

[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 2017, 2016 and 2015 calculations those shares that were contingently issuable upon the satisfaction of the performance conditions as of the end of the respective periods.