CONDENSED CONSOLIDATED STATEMENTS OF INCOME - UNAUDITED - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 244,793	$ 201,704
Cost of revenues (exclusive of depreciation, shown separately below)	128,963	101,096
Other operating expenses:
Research and development	32,591	29,379
Selling, general and administrative	45,918	40,648
Depreciation	5,113	3,914
Restructuring and reorganization charges	115	900
Total operating expenses	212,700	175,937
Operating income	32,093	25,767
Other income (expense):
Interest expense	(4,560)	(4,266)
Amortization of original issue discount	(690)	(652)
Interest and investment income, net	519	811
Loss on extinguishment of debt		(810)
Other, net	(1,511)	(646)
Total other	(6,242)	(5,563)
Income before income taxes	25,851	20,204
Income tax provision	(6,600)	(6,190)
Net income	$ 19,251	$ 14,014
Weighted-average shares outstanding:
Basic	32,128	32,528
Diluted	32,438	33,102
Earnings per common share:
Basic	$ 0.60	$ 0.43
Diluted	$ 0.59	$ 0.42