CONDENSED CONSOLIDATED STATEMENTS OF INCOME (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Income Statement [Abstract]
NET REVENUES	$ 90,144		$ 91,715		$ 262,202		$ 256,677
COST OF REVENUES	41,092		42,941		118,437		121,832
GROSS PROFIT	49,052		48,774		143,765		134,845
OPERATING EXPENSES:
Research and development	13,458		12,984		41,314		38,745
Sales and marketing	11,564		11,212		35,906		33,357
General and administrative	7,155		7,984		22,614		23,784
Total operating expenses	32,177		32,180		99,834		95,886
INCOME FROM OPERATIONS	16,875		16,594		43,931		38,959
OTHER INCOME
Other income, net	381		82		836		864
Total other income	381		82		836		864
INCOME BEFORE PROVISION FOR (BENEFIT FROM) INCOME TAXES	17,256		16,676		44,767		39,823
PROVISION FOR (BENEFIT FROM) INCOME TAXES	1,145		22		(423)		(1,406)
NET INCOME	$ 16,111		$ 16,654		$ 45,190		$ 41,229
EARNINGS PER SHARE:
Basic (in dollars per share)	$ 0.54		$ 0.56		$ 1.50		$ 1.41
Diluted (in dollars per share)	$ 0.52	[1]	$ 0.54	[1]	$ 1.46	[1]	$ 1.36	[1]
SHARES USED IN PER SHARE CALCULATION:
Basic (in shares)	30,013		29,762		30,186		29,235
Diluted (in shares)	30,757	[1]	30,652	[1]	31,053	[1]	30,237	[1]

[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 2014 and 2013 awards in the 2014 and 2013 calculations, respectively, as those shares were not contingently issuable as of the end of the period.