CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
REVENUE	$ 77,550	$ 61,683	$ 177,271	$ 219,762
COST OF SALES	16,123	13,465	35,216	37,762
Gross margin	61,427	48,218	142,055	182,000
OPERATING EXPENSES:
Research and development	13,616	11,596	38,922	34,099
Selling, general and administrative	12,120	11,695	34,473	31,611
Amortization of acquired technology and other intangible assets	5,493	5,498	16,479	16,485
Patent costs	1,937	1,875	5,691	5,096
Royalty and license expense	2,229	1,764	5,028	6,342
Total operating expenses	35,395	32,428	100,593	93,633
OPERATING INCOME	26,032	15,790	41,462	88,367
Interest income, net	2,118	861	5,155	2,328
Other (expense) income, net	(7)	6	(66)	(7)
Interest and other (expense) income, net	2,111	867	5,089	2,321
INCOME BEFORE INCOME TAXES	28,143	16,657	46,551	90,688
INCOME TAX EXPENSE	(5,325)	(3,137)	(6,960)	(19,616)
NET INCOME	$ 22,818	$ 13,520	$ 39,591	$ 71,072
NET INCOME PER COMMON SHARE:
BASIC	$ 0.48	$ 0.28	$ 0.83	$ 1.50
DILUTED	$ 0.48	$ 0.28	$ 0.83	$ 1.49
WEIGHTED AVERAGE SHARES USED IN COMPUTING NET INCOME PER COMMON SHARE:
BASIC	46,869,998	46,801,051	46,841,036	46,716,726
DILUTED	46,914,553	46,871,720	46,893,768	46,793,429
CASH DIVIDENDS DECLARED PER COMMON SHARE	$ 0.06	$ 0.03	$ 0.18	$ 0.09