CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
NET REVENUES		$ 343,989	$ 348,797	$ 347,089
COST OF REVENUES		170,602	159,227	163,853
GROSS PROFIT		173,387	189,570	183,236
OPERATING EXPENSES:
Research and development		57,549	54,981	51,654
Sales and marketing		46,816	47,796	45,466
General and administrative		30,029	30,997	32,050
Total operating expenses		134,394	133,774	129,170
INCOME FROM OPERATIONS		38,993	55,796	54,066
OTHER INCOME:
Interest income		1,019	1,203	736
Interest expense		0	0	(23)
Other, net		(594)	(185)	648
Total other income, net		425	1,018	1,361
INCOME BEFORE INCOME TAXES		39,418	56,814	55,427
PROVISION FOR (BENEFIT FROM) INCOME TAXES		271	(2,730)	(1,839)
NET INCOME		$ 39,147	$ 59,544	$ 57,266
EARNINGS PER SHARE:
Basic (per share)		$ 1.35	$ 1.99	$ 1.95
Diluted (per share)	[1]	$ 1.32	$ 1.93	$ 1.88
SHARES USED IN PER SHARE CALCULATION:
Basic (in shares)		29,001	29,976	29,421
Diluted (in shares)	[1]	29,696	30,829	30,420

[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 all performance-based awards in the 2014 calculation as the performance conditions for those awards were not met as of the end of the period. The Company has included in the 2015 and 2013 calculations those shares that were contingently issuable upon the satisfaction of the performance conditions as of the end of the respective periods.