CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
NET REVENUES		$ 110,085	$ 111,255	$ 322,648	$ 323,506
COST OF REVENUES		53,080	55,542	155,865	163,870
GROSS PROFIT		57,005	55,713	166,783	159,636
OPERATING EXPENSES:
Research and development		17,236	17,340	52,615	51,321
Sales and marketing		13,278	12,768	39,863	38,128
General and administrative		8,466	9,546	26,700	27,015
Total operating expenses		38,980	39,654	119,178	116,464
INCOME FROM OPERATIONS		18,025	16,059	47,605	43,172
OTHER INCOME		1,098	895	2,819	1,866
INCOME BEFORE INCOME TAXES		19,123	16,954	50,424	45,038
PROVISION FOR INCOME TAXES		1,456	448	3,176	531
NET INCOME		$ 17,667	$ 16,506	$ 47,248	$ 44,507
EARNINGS PER SHARE:
Basic (in dollars per share)		$ 0.60	$ 0.55	$ 1.60	$ 1.50
Diluted (in dollars per share)	[1]	$ 0.59	$ 0.54	$ 1.56	$ 1.46
SHARES USED IN PER SHARE CALCULATION:
Basic (in shares)		29,365	29,759	29,558	29,646
Diluted (in shares)		29,998	30,614	30,281	30,472

[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.