CONDENSED CONSOLIDATED STATEMENTS OF INCOME - UNAUDITED - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenues	$ 251,414	$ 213,055	$ 742,063	$ 627,792
Cost of revenues (exclusive of depreciation, shown separately below)	132,054	109,052	393,251	319,640
Other operating expenses:
Research and development	32,551	31,477	95,787	91,809
Selling, general and administrative	46,694	39,243	137,984	120,515
Depreciation	5,365	4,831	15,919	13,293
Restructuring and reorganization charges	1,330	2,799	3,271	7,028
Total operating expenses	217,994	187,402	646,212	552,285
Operating income	33,420	25,653	95,851	75,507
Other income (expense):
Interest expense	(4,390)	(4,456)	(13,448)	(13,202)
Amortization of original issue discount	(709)	(671)	(2,099)	(1,984)
Interest and investment income, net	392	675	1,328	2,256
Loss on extinguishment of debt				(810)
Other, net	108	(709)	(123)	(347)
Total other	(4,599)	(5,161)	(14,342)	(14,087)
Income before income taxes	28,821	20,492	81,509	61,420
Income tax provision	(7,262)	(4,391)	(21,320)	(16,188)
Net income	$ 21,559	$ 16,101	$ 60,189	$ 45,232
Weighted-average shares outstanding:
Basic	32,016	32,507	32,079	32,541
Diluted	32,518	32,806	32,472	32,939
Earnings per common share:
Basic	$ 0.67	$ 0.50	$ 1.88	$ 1.39
Diluted	$ 0.66	$ 0.49	$ 1.85	$ 1.37