CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
REVENUE	$ 56,149	$ 102,513	$ 99,721	$ 158,079
COST OF SALES	11,635	11,310	19,093	24,297
Gross margin	44,514	91,203	80,628	133,782
OPERATING EXPENSES:
Research and development	12,949	10,685	25,306	22,503
Selling, general and administrative	11,562	9,839	22,353	19,916
Amortization of acquired technology and other intangible assets	5,495	5,495	10,986	10,987
Patent costs	2,029	1,674	3,754	3,221
Royalty and license expense	1,568	2,991	2,799	4,578
Total operating expenses	33,603	30,684	65,198	61,205
OPERATING INCOME	10,911	60,519	15,430	72,577
Interest income, net	1,766	796	3,037	1,467
Other (expense) income, net	(12)	6	(59)	(13)
Interest and other (expense) income, net	1,754	802	2,978	1,454
INCOME BEFORE INCOME TAXES	12,665	61,321	18,408	74,031
INCOME TAX EXPENSE	(1,851)	(14,134)	(1,635)	(16,479)
NET INCOME	$ 10,814	$ 47,187	$ 16,773	$ 57,552
NET INCOME PER COMMON SHARE:
BASIC	$ 0.23	$ 0.99	$ 0.35	$ 1.21
DILUTED	$ 0.23	$ 0.99	$ 0.35	$ 1.21
WEIGHTED AVERAGE SHARES USED IN COMPUTING NET INCOME PER COMMON SHARE:
BASIC	46,868,999	46,742,746	46,826,314	46,702,376
DILUTED	46,901,098	46,810,238	46,873,109	46,781,120
CASH DIVIDENDS DECLARED PER COMMON SHARE	$ 0.06	$ 0.03	$ 0.12	$ 0.06